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Soil physical fertility and crop performance as affected by long term application of FYM and inorganic fertilizers in rice–wheat system
Soil & Tillage Research 96 (2007) 64–72 www.elsevier.com/locate/still
Soil physical fertility and crop performance as affected by long term application of FYM and inorganic fertilizers in rice–wheat system Rehana Rasool, S.S. Kukal *, G.S. Hira Department of Soils, Punjab Agricultural University, Ludhiana 141 004, India Received 14 June 2006; received in revised form 5 January 2007; accepted 24 February 2007
Abstract Soil fertility, one of the important determinants of agricultural productivity, is generally thought to be supplemented through the application of nutrients mainly through inorganic fertilizers. The physical fertility of the soil, which creates suitable environment for the availability and uptake of these nutrients, is generally ignored. The present study aims to characterize the soil physical environment in relation to the long term application of farm yard manure (FYM) and inorganic fertilizers in rice–wheat. The treatments during both rice and wheat crops were (i) farm yard manure @ 20 t ha1 (FYM); (ii) nitrogen @ 120 kg ha1 (N120); (iii) nitrogen and phosphorus @ 120 and 30 kg ha1 (N120P30) and (iv) nitrogen, phosphorus and potassium @ 120, 30 and 30 kg ha1 (N120P30K30) in addition to (iv) control treatment, i.e. without any fertilizer and/or FYM addition. The treatments were replicated four times in randomized block design in a sandy loam (typic Ustipsament, non-saline, slightly alkaline). Bulk density, structural stability of soil aggregates and water holding capacity of 0–60 cm soil layer were measured. The average mean weight diameter (MWD) was highest in FYM-plots both in rice (0.237 mm) and wheat (0.249 mm) closely followed by that in N120P30K30 plots. The effect of FYM in increasing the MWD decreased with soil depth. The addition of both FYM and N120P30K30 increased the organic carbon by 44 and 37%, respectively in rice. The total porosity of soil increased with the application of both FYM and N120P30K30 from that in control plots. In 0–15 cm soil layer, the total porosity increased by 25% with FYM from that in control plots. This difference decreased to 13% in 15–30 cm soil layer. The average water holding capacity (WHC) was 16 and 11% higher with FYM and N120P30K30 application from that in control plots. The MWD, total porosity and WHC improved with the application of balanced application of fertilizers. The grain yield and uptake of N, P and K by both rice and wheat were higher with the application of FYM and inorganic fertilizers than in control plots. The carbon sequestration rate after 32 years was maximum (0.31 t ha1 year1) in FYM-plots, followed by 0.26 t ha1 year1 in N120P30K30-plots, 0.19 t ha1 year1 in N120P30 and minimum (0.13 t ha1 year1) in N120-plots. # 2007 Elsevier B.V. All rights reserved. Keywords: Bulk density; Carbon sequestration; FYM; Inorganic fertilizers; Mean weight diameter; Water holding capacity
1. Introduction The declining crop productivity has generally been attributed to the declining soil chemical fertility * Corresponding author. Tel.: +91 161 2401960; fax: +91 161 2400945. E-mail address: [email protected] (S.S. Kukal). 0167-1987/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2007.02.011
(Saunders, 1991; Bhuiyan, 1992; Ali, 1998). Research scientists and policymakers have mainly focused on the issue of chemical soil fertility for enhancing the agricultural productivity. The importance of physical fertility of soil in plant growth has rarely been appreciated (Acharya et al., 1998) because of the concept of soil fertility being related to the extent of the nutrients present in the soil, though their availability is a
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function of the physical environment of the soil. The physical environment of the soil influences the nature of the chemical and biological reactions in the soil necessary for the optimum plant growth (Sharma and Bhushan, 2001). The physical properties of the soil, viz. soil strength, soil water characteristics, drainage, resistance to penetration, aeration, etc. determine the availability of water and hence nutrients, oxygen and the mechanical support to the growing plants. The intensive cultivation results in the degradation of natural soil structure due to the crushing and shearing effect of heavy equipments as well as the depletion of soil organic matter (Anderson et al., 1990; Schjonning et al., 1994). Continuous ploughing at the same depth leads to the formation of a hard pan in the lower layers over a period of time (Aggarwal et al., 1995; Kukal and Aggarwal, 2003a), which hinders the deeper penetration of roots into soil and results in a temporary water logging situation during irrigations (Kukal and Aggarwal, 2003b). Under such situations the application of organic manures can help in regeneration of soil structure (Aggarwal et al., 1995). As the application of organic manures brings about structural improvement, it increases the air capacity, may cause the roots to extend into and exploit a larger volume of soil in addition to increasing water retention in the soil profile (Sarkar et al., 2003; Pernes-Debuyser and Tessier, 2004). It may increase the overall moisture availability to the crop (Dexter, 1988; Ekwue, 1992; El-Shakweer et al., 1998). Thus, the importance of organic matter in relation to the physical fertility of the soil has been widely recognized (Mokwunge et al., 1996; Barzegar et al., 2002). Although organic manure addition and the strengthening of soil biological practices can alleviate nutrient constraints, the problem of soil fertility decline is so serious (Smaling et al., 1997) that it may not be possible to cover all of it with these approaches alone. Chemical fertilizers with instant ability to refurbish depleted nutrients in necessary quantities and forms have come to be recognized as a key component of sustainable soil fertility management and sustainable development of agriculture. The positive effect of the nutrients on the above-ground/below-ground biomass may influence the physical environment of the soil through the addition of higher plant biomass and hence organic matter (Haynes and Naidu, 1998; Sarkar et al., 2003), as well as the modification of the pore geometry of the soil through dense and long root system of the wellfertilized plants (Schjonning et al., 2005). The inorganic fertilizers have been reported to increase rooting depth and root proliferation in cereals (Belford
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et al., 1987; Brown et al., 1987). In addition, the fertilization may also affect the volume of the soil exploited by the roots. The state of Punjab in north India, the most productive state in the country particularly in rice– wheat, has the highest use of chemical fertilizers in the country. Their effect on crop production is mainly attributed to the sufficiency of nutrients (Brar et al., 1997). Though some studies on the long term effect of inorganic and organic fertilizers (Benbi et al., 1998) on soil physical properties have been carried out in isolation in the region, no detailed study on the effect of long term application of organic and inorganic fertilization on soil physical properties has been reported for the cropping system as a whole in the region. The present study thus aims to monitor the effect of long-term application of farmyard manure and inorganic fertilizers on soil physical properties under rice–wheat cropping system. 2. Materials and methods A long-term field experiment, on the application of FYM and inorganic fertilizers in rice–wheat system was selected for the present studies during 2004–2005. The experiment is in progress for last 32 years at Punjab Agricultural University Research Farm, Ludhiana (308540 N latitude and 758480 E longitude above mean sea level of 247 m). 2.1. Climate and soil The climate of the region is tropical semi-arid with an annual rainfall of 700–800 mm of which 80% is received during the 3-month period (July–September). The amount of rain was 444.5 mm in 2004 and 739.7 mm in 2005, with the highest amount of rain in the month of August (225.4 mm in 2004 and 197.6 mm in 2005). The rain during 2005 was normal and well distributed with 40 rainy days in comparison to 32 days during 2004 when it was below long term average. The maximum temperature recorded during 2004 and 2005 was 39.4 8C (May) and 39.3 8C (June), whereas minimum temperature of 7.8 8C (2004) and 4.4 8C (2005) occurred during January and December months, respectively. The soil of the experimental site was sandy loam (Typic ustipsament), low in organic carbon, slightly alkaline, non-saline with low available N, and medium P and high K content. The field capacity (FC) and permanent wilting point (PWP) decreased slightly with depth (Table 1).
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Table 1 Basic soil characteristics Soil characteristics
Soil depth (cm) 0–15
15–30
30–45
45–60
Soil texture Sand (%) Silt (%) Clay (%)
sl 60.1 3.6 33.0 2.2 6.9 0.9
sl 65.1 2.9 30.3 3.6 4.6 1.2
sl 58.2 4.5 35.1 1.9 6.7 1.1
sl 61.1 5.1 33.1 3.4 5.8 0.8
Bulk density (Mg m3)
1.69 0.06
1.75 0.09
1.76 0.04
1.75 0.10
Mass water content (%) FC PWP
15.3 2.9 7.64 1.1
14.7 2.7 7.32 2.0
12.5 1.9 6.24 1.8
11.4 1.7 5.68 0.9
pH EC (dS m1) Organic carbon (%) Available N (kg ha1) Available P (kg ha1) Available K (kg ha1)
8.3 0.4 0.13 0.03 0.29 0.06 88.4 9.6 15.6 2.5 55.0 9.6
7.8 0.3 0.10 0.02 0.23 0.08 – – –
8.1 0.2 0.11 0.04 0.19 0.06 – – –
8.5 0.2 0.12 0.01 0.11 0.04 – – –
2.2. Crop establishment and treatments The field was pre-irrigated 3–4 days in the third week of June 2004 and tilled to 12–13 cm depth twice thereafter at field capacity moisture content to kill the germinated weeds and level the field for better puddling. It was inundated with 5–6 cm standing water and ploughed twice under wet conditions by a tine cultivator followed by one planking with a wooden plank. The rice (cv. PR114) seedlings, about 1-month-old, were transplanted on 18th June 2004 with a spacing of 15 cm 20 cm. The crop was raised as per the recommended practices of Punjab Agricultural University except for the fertilization, which was done as per the treatments. The treatments included (i) FYM (FYM alone @ 20 t ha1, applied at the time of pre-puddling tillage); (ii) N120P30K30 (nitrogen, phosphorus and potash @ 120, 30 and 30 kg ha1); (iii) N120P30 (same as in (ii) except that K application was skipped); (iv) N120 (same as in (iii) except that P and K application was skipped) in comparison to the control treatment (without any FYM or inorganic fertilizer). The treatments were allocated in plots of size 8 m 3 m replicated four times in randomized block design (RBD). Whole of P and K and one-third amount of N fertilizer were added at the time of field preparation. The remaining amount of N was applied at 21 and 42 days after transplanting. The decomposed and dried FYM was spread on the soil surface before pre-puddling tillage. The crop was kept submerged continuously for the first 15 days and thereafter irrigated 2 days after complete disappearance of ponded water in the field. The crop was harvested on
25th October 2004 and the grain yield recorded at 14% moisture content. The same field was again pre-irrigated in the last week of October and disked twice at the field capacity moisture content. It was disked and ploughed twice the next day and thereafter planked once. The wheat (cv. PBW343) was sown on 4th November 2004 and the crop was raised as per the recommended practices of Punjab Agricultural University, except fertilization, which was done as per the treatments. The fertilizer treatments in case of wheat were the same as outlined above in rice crop. Same plots received similar treatments during both the crop seasons. The crop was irrigated at 21, 52 and 131 DAS as per the recommended practice of Punjab Agricultural University. The crop was harvested on 15th April 2005 and the grain yield recorded. 2.3. Observations The soil samples for aggregate size distribution were collected at the depths of 0–15, 15–30, 30–45 and 45– 60 cm from each treatment at the harvest of rice and wheat crops. Big clods (40–50 cm diameter) of soil were sampled for the above-mentioned depth and airdried, made to fall from a height of 60–70 cm on a vegetated surface so as to get broken at natural points of cleavage. These were then passed through 8-mm sieve and those retained on 4-mm sieve were used for aggregate analysis by the wet sieving technique as described by Kemper and Rosenau (1986). The undisturbed soil cores in one edge-sharpened galvanized iron (metallic) cylinders of 7.5 cm internal
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5.0 cm I.D. and 4 cm height with perforated bottom and a filter paper disc fixed with a steel ring at the bottom end) for the soil samples drawn at the harvest of rice and wheat crops from the soil at 0–15, 15–30, 30–45 and 45–60 cm depth. Using the particle density of the soil samples, the total porosity of the soil was calculated. The data so obtained for each observation was analyzed statistically using factorials in randomized block design (RBD) as described by Steel and Torrie (1960).
diameter and 7.5 cm height were collected at the harvest of rice and wheat crops with the help of a small hammer and a piece of wood from all the treatments in 0–15, 15– 30, 30–45 and 45–60 cm soil layers. The precautions were taken to reduce the disturbance of soil within the metallic cylinder during sampling, which was done at 10–12% soil moisture content. The soil cores along with the metallic cylinder were excavated with the help of a spade and the extra soil was retained on both sides of excavated cores and carefully preserved in polythene bags. The soil cores were dried in an oven at 105 8C for 24 h to get dry weight of the soil. The ratio of dry weight of soil core and internal volume of the metallic cylinder was expressed as bulk density in Mg m3. The soil organic carbon was determined by Walkley and Black’s titration method (Piper, 1950). The soil organic carbon (SOC) pools were calculated for each treatment separately at depths 0–15, 15–30, 30–45 and 45–60 cm. From mean pool values, carbon sequestration rate was calculated separately for each treatment over control (without fertilization) after 22-year period of experimentation. The maximum water holding capacity (WHC) was calculated with the help of Keen’s box (steel box of
The wet stability of aggregates, expressed in terms of mean weight diameter (MWD), in relation to inorganic fertilizers and FYM is presented in Table 2. The average MWD was highest in the FYM-treated plots both at the harvest of rice (0.237 mm) and wheat (0.249 mm), followed by that in N120P30K30 treatments. The application of balanced fertilizers helped improve the MWD in both rice and wheat. The FYM improved the MWD by 64 and 67% at the end of rice and wheat crops, whereas N120P30K30 increased the MWD by 58 and
Table 2 Mean weight diameter (MWD) (mm) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Table 3 Organic carbon (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Treatments
Treatments
Rice Control FYM N120 N120P30 N120P30K30 Mean
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
0.145 0.506 0.202 0.274 0.379
0.087 0.237 0.153 0.130 0.220
0.060 0.116 0.086 0.118 0.129
0.049 0.088 0.053 0.074 0.083
0.301
0.165
0.102
0.073
0.085 0.237 0.124 0.149 0.203
Mean
Rice Control FYM N120 N120P30 N120P30K30
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
0.30 0.62 0.34 0.38 0.53
0.20 0.34 0.25 0.27 0.30
0.15 0.22 0.17 0.19 0.20
0.09 0.18 0.10 0.10 0.17
0.43
0.27
0.19
0.13
0.19 0.34 0.22 0.24 0.30
LSD (0.05) Fertilization = 0.023 Soil depth = 0.022 Fertilization soil depth = 0.050
0.129 0.524 0.154 0.244 0.309
0.085 0.224 0.114 0.116 0.213
0.064 0.157 0.069 0.096 0.141
0.054 0.092 0.064 0.071 0.088
0.272
0.150
0.105
0.074
LSD (0.05) Fertilization = 0.006 Soil depth = 0.007 Fertilization soil depth = 0.013
3.1. Soil aggregation
Mean
LSD (0.05) Fertilization = 0.009 Soil depth = 0.008 Fertilization soil depth = 0.018 Wheat Control FYM N120 N120P30 N120P30K30
3. Results and discussion
0.083 0.249 0.100 0.132 0.188
Wheat Control FYM N120 N120P30 N120P30K30 Mean
0.29 0.51 0.39 0.44 0.49
0.23 0.34 0.27 0.29 0.31
0.19 0.26 0.22 0.22 0.24
0.11 0.18 0.13 0.15 0.16
0.42
0.29
0.23
0.15
LSD (0.05) Fertilization = 0.029 Soil depth = 0.026 Fertilization soil depth = 0.059
0.21 0.32 0.25 0.28 0.30
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helped increase the organic C content by 44 and 37%, respectively in rice crop (Table 3). The increase was more pronounced in the surface layers. The increased organic C content might be responsible for stabilization of aggregates and hence higher MWD with the application of FYM and inorganic fertilizers.
56%, respectively, from that in control plots. There was significant decrease in MWD with the soil depth. It decreased 0.301 mm in 0–15 cm to 0.165 mm in 15– 30 cm, 0.102 mm in 30–45 cm, to 0.070 mm in 45– 60 cm soil layers in rice. A significant interaction could be observed between the treatments and soil depth in both the crops. The effect of FYM in increasing the MWD decreased with soil depth. At the end of rice harvest, FYM increased MWD by 71, 64, 48 and 44% in 0–15, 15–30, 30–45 and 45–60 cm soil layers, respectively. On the other hand, the correspondence increase in MWD with N120P30K30 was 62, 60, 53 and 41%, respectively. Similar trend could be observed at the end of wheat crop. Since the effect of FYM in increasing MWD was pronounced till the deeper layers, it indicates that apart from direct effect of FYM as a binding agent (Bhushan and Sharma, 2002), it indirectly might have helped in increasing MWD through increased root biomass (mainly root hair) and hence organic matter. Similarly the inorganic fertilizers might have helped in increasing the root biomass than in control plots which ultimately helped in increasing the MWD (Haynes and Naidu, 1998). The addition of FYM and inorganic fertilizers
The soil bulk density recorded at the harvest of rice and wheat (Table 4) shows that FYM helped decrease the bulk density significantly in comparison to that of control plots in all the soil layers (0–60 cm). However, the decrease was more in upper soil layers (0–15 and 15–30 cm) than in lower layers. In N120- and N120P30 plots, the bulk density of all the layers was at par with that in control plots. The balanced use of fertilizers (N120P30K30) significantly decreased bulk density of all the layers from that in control, the decrease being more in upper layers than in lower layers, both after rice and wheat crops. As in MWD, the mean total porosity of soil during rice crop increased significantly with the application of FYM and inorganic fertilizers (Table 5) in both rice and
Table 4 Soil bulk density (Mg m3) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Table 5 Total soil porosity (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Treatments
Treatments
Rice Control FYM N120 N120P30 N120P30K30
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
1.69 1.60 1.67 1.65 1.63
1.75 1.69 1.73 1.72 1.70
1.76 1.70 1.74 1.73 1.72
1.75 1.71 1.75 1.74 1.73
Mean
Rice Control FYM N120 N120P30 N120P30K30 Mean
LSD (0.05) Fertilization = 0.05 Soil depth = 0.06 Fertilization soil depth = 0.03 Wheat Control FYM N120 N120P30 N120P30K30
3.2. Soil bulk density and total porosity
1.69 1.58 1.65 1.62 1.60
1.75 1.63 1.68 1.67 1.65
Mean LSD (0.05) Fertilization = 0.06 Soil depth = 0.04 Fertilization soil depth = 0.05
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
32.2 40.5 35.3 36.4 38.7
30.1 36.3 34.7 34.2 35.4
29.5 32.3 30.2 30.4 31.8
27.2 32.5 30.6 30.2 31.6
36.6
34.1
30.8
30.4
29.7 35.4 32.7 32.8 33.4
LSD (0.05) Fertilization = 0.025 Soil depth = NS Fertilization soil depth = 0.058 1.75 1.65 1.72 1.70 1.68
1.75 1.70 1.73 1.72 1.71
Wheat Control FYM N120 N120P30 N120P30K30 Mean
37.1 42.5 38.2 39.3 41.4
32.5 36.3 33.6 34.1 35.4
30.2 34.7 33.4 31.1 33.3
29.1 32.4 31.3 30.2 31.1
39.6
34.4
32.5
30.8
LSD (0.05) Fertilization = 0.033 Soil depth = NS Fertilization soil depth = NS
32.2 36.5 34.1 33.7 35.3
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wheat crops. The addition of FYM promotes the total porosity of the soils as the microbial decomposition products of organic manures such as polysaccharides and bacterial gums are known to act as soil particle binding agents. These binding agents increase the porosity and decrease the bulk density of the soil (Bhatia and Shukla, 1982) by improving the aggregation. Increase in soil porosity with fertilization has also been reported by Yeoh and Oades (1981), Schjonning et al. (1994) and Prasad and Sinha (2000). The total porosity increased with the application of balanced fertilizers. It decreased with depth, though nonsignificantly in rice. There was significant difference in the effect of FYM and other treatments with depth. In 0–15 cm soil layer, the total porosity increased by 25% with the application of FYM from that in control in rice crop. This difference decreased to 13% in 15–30 cm soil layer. However, in the deeper layers, the difference in total porosity among the treatments was not significant. Similar was the case with N120P30K30 treatment, where the increase in total porosity from that in control decreased with soil depth. Thus, the effect of FYM and inorganic fertilizers in increasing the total soil porosity was more pronounced in the surface soil layers. The higher total porosity of the soil particularly of the surface layer helps in ready exchange of O2 and CO2 between the soil and the atmosphere, thereby, promoting better root growth in the soil. Similar was the trend in wheat crop except that total soil porosity was affected equally in all the soil layers. 3.3. Maximum water holding capacity The average WHC of soil during rice was (16%) higher in FYM plots than in control plots, whereas it was 11% higher in N120P30K30 plots (Table 6). The application of balanced inorganic fertilizers increased the water holding capacity of soils. The WHC of unbalanced fertilizer plots was not significantly different from that in control plots. The higher organic carbon content in FYM-treated plots could be responsible for increasing the WHC of the soil, the difference is being more pronounced in surface soil layers though the balanced application of NPK enhanced the organic carbon restoration probably due to higher root biomass. The application of inorganic fertilizers thus improves the WHC of soil (Singh et al., 2003). The difference in WHC of FYM and inorganic fertilizers treated plots was significant in both rice and wheat crops. It, however, did not vary significantly with soil depth. At the harvest of rice crop, the WHC was 17.3, 15.6, 17.7 and 15.1% higher in FYM treated plots than in control plots in 0–5,
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Table 6 Maximum water holding capacity (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system Treatments
Rice Control FYM N120 N120P30 N120P30K30 Mean
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
31.6 38.2 32.7 33.4 34.8
30.2 35.9 31.6 32.4 33.8
28.3 34.4 30.7 31.0 32.4
27.5 32.4 29.6 30.8 31.3
34.1
32.8
31.4
30.3
29.4 35.2 31.1 31.9 33.1
LSD (0.05) Fertilization = 1.25 Soil depth = NS Fertilization soil depth = 2.50 Wheat Control FYM N120 N120P30 N120P30K30 Mean
30.6 41.2 34.4 35.8 38.4
29.3 38.4 32.4 33.7 33.7
25.0 34.6 31.8 32.6 32.7
22.7 33.8 29.1 30.1 31.2
36.1
33.5
31.3
29.4
26.9 37.0 31.9 33.0 34.0
LSD (0.05) Fertilization = 1.35 Soil depth = 1.21 Fertilization soil depth = 2.70
15–30, 30–45 and 45–60 cm soil layers, respectively. The corresponding values of increase in case of N120P30K30 were 9.1, 10.6, 12.6 and 12.0%, respectively in the 0–15, 15–30, 30–45 and 45–60 cm soil layer. The higher WHC in the surface layer due to FYM is expected because of its addition in surface layers, whereas in the subsurface layers the increase in WHC could be due to the increased root biomass with FYM or inorganic fertilizers (Singh et al., 2003) and hence organic C. 3.4. SOC pool and C sequestration The SOC pools for different treatments (Table 7) shows that highest C (31.4 Mg ha1) was pooled in FYM-treated plots and lowest (21.3 Mg ha1) in control plots. The N120 plots pooled 19.7% higher SOC than control plots. Addition of P and P + K fertilizers improved SOC pool by 28.6 and 39%, respectively. There was no difference in mean (0–60 cm) SOC pool in FYM- and N120P30K30-plots. The SOC pool decreased significantly with soil depth in all the treatments. Fertilizer or manure application would be expected to increase SOC, because of greater C input associated with enhanced primary production and crop residues returned
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Table 7 Soil organic carbon pools (Mg ha1) and carbon sequestration rate as affected by inorganic fertilization and FYM treatments under rice–wheat system Treatments
Soil depth (cm) 0–15
15–30
30–45
45–60
0–60
Control FYM N120 N120P30 N120P30K30
7.35 12.1 9.65 10.7 11.8
6.04 8.31 6.80 7.26 7.67
4.99 6.44 5.68 5.61 6.05
2.89 4.59 3.37 3.87 4.10
21.3 31.4 25.5 27.4 29.6
Mean
10.3
7.22
5.75
3.76
27.0
C sequestration rate (Mg ha1 year1) – 0.31 0.13 0.19 0.26
LSD (0.05) for SOC pools Fertilization = 4.3 Soil depth = 2.1 Fertilization soil depth = NS
to the soil. Parker et al. (2002) reported 7–20% greater organic C in the surface 5 cm of soil in a cotton-rye (Secale cereale L.) cropping system with a poultry litter than with commercial fertilizer application. Application of dairy manure increased SOC by 2.7 Mg C ha1 in a cotton-corn rotation with cover crops (Terra, 2004). The carbon sequestration rate over 32 years of experimentation was maximum (0.31 Mg ha1 year1) in FYM-plots, followed by 0.26 Mg ha1 year1 in N120P30K30-plots, 0.19 Mg ha1 year1 in N120P30 and minimum (0.13 Mg ha1 year1) in N120-plots (Table 7). This shows that balanced fertilization helps in sequestering higher carbon than that sequestered by unbalanced fertilization. Franzluebbers (2005) estimated that the net C offset due to N fertilization could be optimized at 0.24 Mg C ha1 year1 with the application of 108 kg N ha1 year1 assuming a C cost of 1.23 kg C kg1 N N fertilizer for the manufacture, distribution and application of fertilizer N (Izaurralde et al., 1998). The exploitative practices in intensive agriculture viz. removal of plant residues, imbalanced nutrition are mainly responsible for increased carbon emissions from the soils (Lal, 2003). More research is needed urgently to investigate the effect of animal manure application on SOC sequestration, yield potential and quality characteristics and nutrient leaching in rice–wheat system. The widespread availability of dairy manure (FYM) in the region dictates a need for greater understanding of how nutrients can be recycled among agricultural enterprises more effectively to meet production and environmental goals. 3.5. Crop performance The grain yield of rice was significantly higher (49.4%) in FYM-treated plots than in control plots. It
was closely followed by (47%) higher than that in N120P30K30-plots (Table 8). However, there was no significant difference in the grain yield of FYM and N120P30K30-plots. The balanced fertilization improved the grain yield of rice. Similar was the trend in straw yield except that it was non-significantly higher in N120P30K30-plots. The uptake of N, P and K followed the trend as in the grain yield of rice. It was highest in FYM-treated plots, followed by N120P30K30-plots but was significantly lower in the control treatment. Better physical environment coupled with sufficiency of water and nutrients helped in better uptake of water and nutrients and hence the yield of rice. Yang et al. (2004) observed that incorporation of organic residues significantly increased uptake of N, P and K by rice plants and facilitated the allocation and Table 8 Yield and nutrient uptake by rice–wheat system under inorganic fertilization and FYM treatments Treatments
Grain yield (Mg ha1)
Nutrient uptake (kg ha1)
Grain
Straw
N
P
K
Rice Control FYM N120 N120P30 N120P30K30 LSD (0.05)
5.30 7.92 6.85 7.47 7.77 1.60
11.5 20.4 16.0 19.2 21.2 4.12
70.5 105.3 91.1 99.3 103.3
12.2 18.2 15.7 17.2 17.9
14.8 22.2 19.2 20.9 21.7
Wheat Control FYM N120 N120P30 N120P30K30 LSD (0.05)
2.06 4.83 2.99 4.05 4.37 0.72
8.35 15.3 10.6 13.5 13.9 2.52
39.0 105.3 55.7 81.1 93.9
6.40 16.5 9.28 13.8 14.9
10.2 28.0 15.5 21.9 24.5
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transfer of nutrient elements to the rice ears and grains. Similar trend was observed in the performance of wheat after rice where the FYM-treated plots recorded highest grain (4.83 Mg ha1) and straw (15.3 Mg ha1) yields followed by that in N120P30K30-plots (4.37 and 13.9 Mg ha1, respectively). The uptake of N, P and K by wheat grains was higher in FYM- and N120P30K30plots. Sharma et al. (2003) observed that the addition of Lantana spp. @ 10, 20 and 30 Mg ha1 increased wheat yields by 11, 14 and 20% from that in control, whereas it increased the total (rice + wheat) system productivity by 15, 20 and 26% over controls and at the same time saved NPK fertilizers. The better crop yields of rice and wheat with organic and inorganic balanced fertilization helps improve soil physical environment, pool greater carbon content and better C sequestration in the soils. 4. Conclusions The soil physical properties viz. MWD, total porosity and maximum water holding capacity increased equally with the application of FYM and N120P30K30. The increase in total porosity was more pronounced in the surface layers whereas the MWD increased in the deeper layers as well and water holding capacity was same throughout the profile. The soil bulk density was lower in FYM and N120P30K30 plots than in control plots especially in the surface layers. The FYM and N120P30K30 had similar effect on SOC pool, whereas FYM sequestered more C in FYM plots (0.31 Mg ha1 year1) than in N120P30K30 (0.26 Mg ha1 year1). The application of balanced fertilization increased C sequestration. The uptake of N, P and K and grain yields of both rice and wheat were higher with the application of FYM and N120P30K30. References Acharya, C.L., Bishnoi, S.K., Yaduvanshi, H.S., 1998. Effect of longterm application of fertilizers, and organic and inorganic amendments under continuous cropping on soil physical and chemical properties in an Alfisol. Indian J. Agric. Sci. 58, 509–516. Aggarwal, G.C., Sidhu, A.S., Sekhon, N.K., Sandhu, K.S., Sur, H.S., 1995. Puddling and N management effects on crop response in a rice–wheat cropping system. Soil Till. Res. 36, 129–139. Ali, M.M., 1998. Degradation of paddy soils during the period 1967– 95 in Bangldesh. Ph. D. Thesis, Faculty of Life and Environment Sciences, Shimane University, Matsue 690, Japan. Anderson, S.M., Gantzer, C.J., Brown, J.R., 1990. Soil physical properties after 100 years of continuous cultivation. J. Soil Water Conser. 45, 117–121.
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Barzegar, A.R., Yousefi, A., Daryashenas, A., 2002. The effect of addition of different amounts and types of organic materials on soil physical properties and yield of wheat. Plant Soil 247, 295– 301. Belford, R.K., Klepper, B., Rickman, R.W., 1987. Studies of intact shoot root systems of field grown winter wheat. II. Root and shoot developmental patterns as related to nitrogen fertilizer. Agron. J. 79, 310–319. Benbi, D.K., Biswas, C.R., Bawa, S.S., Kumar, K., 1998. Influence of farmyard manure, inorganic fertilizers and weed control practices on some soil physical properties in a long term experiment. Soil Use Manage. 14, 52–54. Bhatia, K.S., Shukla, K.K., 1982. Effect of continuous application of fertilizers and manure on some physical properties of eroded alluvial soil. J. Indian Soc. Soil Sci. 30, 33–36. Bhuiyan, N.I., 1992. Intensive cropping and soil nutrient balance. In: A key note paper presented at the international conference on ‘‘Improving soil management for intensive cropping in the tropics and subtropics’’, BARC, Dhaka, Bangladesh, December 1–3. Bhushan, L., Sharma, P.K., 2002. Long-term effects of lantana (Lantana spp. L.) residue additions on soil physical properties under rice–wheat cropping I. Soil consistency, surface cracking and clod formation. Soil Till. Res. 65, 157–167. Brar, S.P.S., Rekhi, R.S., Benbi, D.K., 1997. Long term effect of N, P, K and Zn application on crop yield and soil properties in a maize what system. In: Proceedings of 3rd Agricultural Science Congress PAU, Ludhiana, March 12–15, p. 1997. Brown, S.C., Keatinge, J.D.H., Gregory, P.J., Cooper, P.J.M., 1987. Effect of fertilizer, variety and location on barley production under rainfed condition in northern Syria. I. Root and shoot growth. Field Crops Res. 16, 53–66. Dexter, A.R., 1988. Advances in characterization of soil structure. Soil Till. Res. 11, 199–238. Ekwue, E.I., 1992. Effect of organic and fertilizer treatments on soil physical properties and erodibility. Soil Till Res. 22, 199–209. El-Shakweer, M.H.A., El-Sayad, E.A., Ewees, M.S.A., 1998. Soil and plant analysis as a guide for interpretation of the improvement efficiency of organic conditioners added to different soil in Egypt. Comm. Soil Sci. Plant Anal. 29, 2067–2088. Franzluebbers, A.J., 2005. Soil organic carbon sequestration and agricultural GHG emissions in the southeastern USA. Soil Till. Res. 83, 120–147. Haynes, R.J., Naidu, R., 1998. Influence of lime, fertilizer and manure applications on soil organic matter content and soil physical conditions: A review. Nutr. Cycl. Agroecosyst. 51, 123–137. Izaurralde, R.C., McGill, W.B., Bryden, A., Graham, S., Ward, M., Dickey, P., 1998. Scientific challenges in developing a plan to predict and verify C storage in Canadian Prairie soils. In: Lal, R. (Ed.), Management of Carbon Sequestration in Soil. CRC Press, Broca, Raton, FL, pp. 443–446. Kemper, W.D., Rosenau, R.C., 1986. Aggregate stability and size distribution. In: Klute, A. (Ed.), Methods of Soil Analysis. I. Agronomy Monograph No. 9. second ed. pp. 771–798. Kukal, S.S., Aggarwal, G.C., 2003a. Puddling depth and intensity effects in rice–wheat system on a sandy loam soil. I. Development of subsurface compaction. Soil Till. Res. 72, 1–8. Kukal, S.S., Aggarwal, G.C., 2003b. Puddling depth and intensity effects in rice–wheat system on a sandy loam soil. II. Water use and crop performance. Soil Till. Res. 74, 37–45. Lal, R., 2003. Soil erosion and the global carbon budget. Environ. Intern. 29, 437–450.
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Mokwunge, A.U., deJager, A., Smaling, E.M.A., 1996. Pestoring and maintaining the productivity of west African soil: key to sustainable development. In: Miscellaneous Fertilizers Studies No. 14. Parker, M.A., Nyakatawa, E.Z., Reddy, K.C., Reeves, D.W., 2002. Soil carbon and nitrogen as influenced by tillage and poultry litter in north Alabama. In: van Santen, E. (Ed.), Making Conservation Tillage Conventional: BUILDING a FUture on 25 years of Research. Proceedings of 25th Annual Southern Conservation Tillage Conference Sustainable Agriculture, Auburn, AL, 24– 26 June 2002, pp. 283–287. Pernes-Debuyser, A., Tessier, D., 2004. Soil physical properties affected by long-term fertilization. Eur. J. Soil Sci. 55, 505–512. Piper, C.S., 1950. Soil and Plant Analysis. International Science Publishers, New York, USA. Prasad, B., Sinha, S.K., 2000. Long-term effects of fertilizers and organic manures on crop yields, nutrient balance and soil properties in rice–wheat cropping system in Bihar. In: Abrol, I.P., Bronson, K.f., Duxbury, J.M., Gupta, R.K. (Eds.), Long term soil fertility experiments in rice–wheat cropping systems. Rice– Wheat Consortium Paper Series 6. New Delhi, India: Rice– Wheat Consortium for the Indo–Gangetic Plains. pp. 105–119. Sarkar, S., Singh, S.R., Singh, R.P., 2003. The effect of organic and inorganic fertilizers on soil physical condition and the productivity of a rice–wheat cropping sequence in India. J. Agric. Sci. 140, 419–425. Saunders, D.A., 1991. Report of an on farm survey: Jessore and Kustia: Farmer’s practices and perceptions. Monograph No. 8. Wheat Research Center, BARI, Dinajpur, Bangladesh. Schjonning, P., Christensen, B.T., Carstensen, B., 1994. Physical and chemical properties of a sandy loam receiving animal manure, mineral fertilizer or no fertilizer for 90 years. Eur. J. Soil Sci. 45, 257–268.
Schjonning, P., Iversen, B.V., Munkholm, L.J., Labouriau, R., Jacobsen, O.H., 2005. Pore characteristics and hydraulic properties of a sandy loam supplied for a century with either animal manure of mineral fertilizers. Soil Use Manage. 21, 265–275. Sharma, P.K., Bhushan, L., 2001. Physical characterization of a soil amended with organic residues in a rice–wheat cropping system using a single value soil physical index. Soil Till. Res. 60, 143– 152. Sharma, P.K., Ladha, J.K., Verma, T.S., Bhagat, R.M., Padre, A.T., 2003. Rice–wheat productivity and nutrient status in a lantana(Lantana spp.) amended soil. Biol. Fertil. Soils 37, 108–114. Singh, M.V., Manna, M.C., Wanjari, R.H., Singh, Y.V., Rajput, G.S., 2003. Comprehensive report, NATP-RRPS 19—organic pools and dynamics in relation to land use, tillage and agronomic practices for maintenance of soil fertility. IISS, Bhopal, pp. 1–92. Smaling, E.M.A., Nandwa, S.M., Janseen, B.H., 1997. Soil fertility in African is at stake. In: Buresh, R.J., Sanchez, P.A., Calhoum, F. (Eds.), Replenishing Soil Fertility in African. SSSA special publication No. 51, Wisconsin, USA, pp. 47–61. Steel, R.G.D., Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, pp. 232–251. Terra, J.A., 2004. Soil management and landscape variability impacts on field scale cotton and corn productivity. Ph.D. Dissertation, Auburn University, Auburn, AL. Yang, C., Yang, L., Yang, Y., Ouyang, Z., 2004. Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils. Agric. Water Manage. 70, 67– 81. Yeoh, N.S., Oades, J.M., 1981. Properties of soils and clays after acid treatment. II. Urrbrae fine sandy loam. Aust. J. Soil Res. 19, 159– 166.
Soil physical fertility and crop performance as affected by long term application of FYM and inorganic fertilizers in rice–wheat system Rehana Rasool, S.S. Kukal *, G.S. Hira Department of Soils, Punjab Agricultural University, Ludhiana 141 004, India Received 14 June 2006; received in revised form 5 January 2007; accepted 24 February 2007
Abstract Soil fertility, one of the important determinants of agricultural productivity, is generally thought to be supplemented through the application of nutrients mainly through inorganic fertilizers. The physical fertility of the soil, which creates suitable environment for the availability and uptake of these nutrients, is generally ignored. The present study aims to characterize the soil physical environment in relation to the long term application of farm yard manure (FYM) and inorganic fertilizers in rice–wheat. The treatments during both rice and wheat crops were (i) farm yard manure @ 20 t ha1 (FYM); (ii) nitrogen @ 120 kg ha1 (N120); (iii) nitrogen and phosphorus @ 120 and 30 kg ha1 (N120P30) and (iv) nitrogen, phosphorus and potassium @ 120, 30 and 30 kg ha1 (N120P30K30) in addition to (iv) control treatment, i.e. without any fertilizer and/or FYM addition. The treatments were replicated four times in randomized block design in a sandy loam (typic Ustipsament, non-saline, slightly alkaline). Bulk density, structural stability of soil aggregates and water holding capacity of 0–60 cm soil layer were measured. The average mean weight diameter (MWD) was highest in FYM-plots both in rice (0.237 mm) and wheat (0.249 mm) closely followed by that in N120P30K30 plots. The effect of FYM in increasing the MWD decreased with soil depth. The addition of both FYM and N120P30K30 increased the organic carbon by 44 and 37%, respectively in rice. The total porosity of soil increased with the application of both FYM and N120P30K30 from that in control plots. In 0–15 cm soil layer, the total porosity increased by 25% with FYM from that in control plots. This difference decreased to 13% in 15–30 cm soil layer. The average water holding capacity (WHC) was 16 and 11% higher with FYM and N120P30K30 application from that in control plots. The MWD, total porosity and WHC improved with the application of balanced application of fertilizers. The grain yield and uptake of N, P and K by both rice and wheat were higher with the application of FYM and inorganic fertilizers than in control plots. The carbon sequestration rate after 32 years was maximum (0.31 t ha1 year1) in FYM-plots, followed by 0.26 t ha1 year1 in N120P30K30-plots, 0.19 t ha1 year1 in N120P30 and minimum (0.13 t ha1 year1) in N120-plots. # 2007 Elsevier B.V. All rights reserved. Keywords: Bulk density; Carbon sequestration; FYM; Inorganic fertilizers; Mean weight diameter; Water holding capacity
1. Introduction The declining crop productivity has generally been attributed to the declining soil chemical fertility * Corresponding author. Tel.: +91 161 2401960; fax: +91 161 2400945. E-mail address: [email protected] (S.S. Kukal). 0167-1987/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2007.02.011
(Saunders, 1991; Bhuiyan, 1992; Ali, 1998). Research scientists and policymakers have mainly focused on the issue of chemical soil fertility for enhancing the agricultural productivity. The importance of physical fertility of soil in plant growth has rarely been appreciated (Acharya et al., 1998) because of the concept of soil fertility being related to the extent of the nutrients present in the soil, though their availability is a
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function of the physical environment of the soil. The physical environment of the soil influences the nature of the chemical and biological reactions in the soil necessary for the optimum plant growth (Sharma and Bhushan, 2001). The physical properties of the soil, viz. soil strength, soil water characteristics, drainage, resistance to penetration, aeration, etc. determine the availability of water and hence nutrients, oxygen and the mechanical support to the growing plants. The intensive cultivation results in the degradation of natural soil structure due to the crushing and shearing effect of heavy equipments as well as the depletion of soil organic matter (Anderson et al., 1990; Schjonning et al., 1994). Continuous ploughing at the same depth leads to the formation of a hard pan in the lower layers over a period of time (Aggarwal et al., 1995; Kukal and Aggarwal, 2003a), which hinders the deeper penetration of roots into soil and results in a temporary water logging situation during irrigations (Kukal and Aggarwal, 2003b). Under such situations the application of organic manures can help in regeneration of soil structure (Aggarwal et al., 1995). As the application of organic manures brings about structural improvement, it increases the air capacity, may cause the roots to extend into and exploit a larger volume of soil in addition to increasing water retention in the soil profile (Sarkar et al., 2003; Pernes-Debuyser and Tessier, 2004). It may increase the overall moisture availability to the crop (Dexter, 1988; Ekwue, 1992; El-Shakweer et al., 1998). Thus, the importance of organic matter in relation to the physical fertility of the soil has been widely recognized (Mokwunge et al., 1996; Barzegar et al., 2002). Although organic manure addition and the strengthening of soil biological practices can alleviate nutrient constraints, the problem of soil fertility decline is so serious (Smaling et al., 1997) that it may not be possible to cover all of it with these approaches alone. Chemical fertilizers with instant ability to refurbish depleted nutrients in necessary quantities and forms have come to be recognized as a key component of sustainable soil fertility management and sustainable development of agriculture. The positive effect of the nutrients on the above-ground/below-ground biomass may influence the physical environment of the soil through the addition of higher plant biomass and hence organic matter (Haynes and Naidu, 1998; Sarkar et al., 2003), as well as the modification of the pore geometry of the soil through dense and long root system of the wellfertilized plants (Schjonning et al., 2005). The inorganic fertilizers have been reported to increase rooting depth and root proliferation in cereals (Belford
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et al., 1987; Brown et al., 1987). In addition, the fertilization may also affect the volume of the soil exploited by the roots. The state of Punjab in north India, the most productive state in the country particularly in rice– wheat, has the highest use of chemical fertilizers in the country. Their effect on crop production is mainly attributed to the sufficiency of nutrients (Brar et al., 1997). Though some studies on the long term effect of inorganic and organic fertilizers (Benbi et al., 1998) on soil physical properties have been carried out in isolation in the region, no detailed study on the effect of long term application of organic and inorganic fertilization on soil physical properties has been reported for the cropping system as a whole in the region. The present study thus aims to monitor the effect of long-term application of farmyard manure and inorganic fertilizers on soil physical properties under rice–wheat cropping system. 2. Materials and methods A long-term field experiment, on the application of FYM and inorganic fertilizers in rice–wheat system was selected for the present studies during 2004–2005. The experiment is in progress for last 32 years at Punjab Agricultural University Research Farm, Ludhiana (308540 N latitude and 758480 E longitude above mean sea level of 247 m). 2.1. Climate and soil The climate of the region is tropical semi-arid with an annual rainfall of 700–800 mm of which 80% is received during the 3-month period (July–September). The amount of rain was 444.5 mm in 2004 and 739.7 mm in 2005, with the highest amount of rain in the month of August (225.4 mm in 2004 and 197.6 mm in 2005). The rain during 2005 was normal and well distributed with 40 rainy days in comparison to 32 days during 2004 when it was below long term average. The maximum temperature recorded during 2004 and 2005 was 39.4 8C (May) and 39.3 8C (June), whereas minimum temperature of 7.8 8C (2004) and 4.4 8C (2005) occurred during January and December months, respectively. The soil of the experimental site was sandy loam (Typic ustipsament), low in organic carbon, slightly alkaline, non-saline with low available N, and medium P and high K content. The field capacity (FC) and permanent wilting point (PWP) decreased slightly with depth (Table 1).
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Table 1 Basic soil characteristics Soil characteristics
Soil depth (cm) 0–15
15–30
30–45
45–60
Soil texture Sand (%) Silt (%) Clay (%)
sl 60.1 3.6 33.0 2.2 6.9 0.9
sl 65.1 2.9 30.3 3.6 4.6 1.2
sl 58.2 4.5 35.1 1.9 6.7 1.1
sl 61.1 5.1 33.1 3.4 5.8 0.8
Bulk density (Mg m3)
1.69 0.06
1.75 0.09
1.76 0.04
1.75 0.10
Mass water content (%) FC PWP
15.3 2.9 7.64 1.1
14.7 2.7 7.32 2.0
12.5 1.9 6.24 1.8
11.4 1.7 5.68 0.9
pH EC (dS m1) Organic carbon (%) Available N (kg ha1) Available P (kg ha1) Available K (kg ha1)
8.3 0.4 0.13 0.03 0.29 0.06 88.4 9.6 15.6 2.5 55.0 9.6
7.8 0.3 0.10 0.02 0.23 0.08 – – –
8.1 0.2 0.11 0.04 0.19 0.06 – – –
8.5 0.2 0.12 0.01 0.11 0.04 – – –
2.2. Crop establishment and treatments The field was pre-irrigated 3–4 days in the third week of June 2004 and tilled to 12–13 cm depth twice thereafter at field capacity moisture content to kill the germinated weeds and level the field for better puddling. It was inundated with 5–6 cm standing water and ploughed twice under wet conditions by a tine cultivator followed by one planking with a wooden plank. The rice (cv. PR114) seedlings, about 1-month-old, were transplanted on 18th June 2004 with a spacing of 15 cm 20 cm. The crop was raised as per the recommended practices of Punjab Agricultural University except for the fertilization, which was done as per the treatments. The treatments included (i) FYM (FYM alone @ 20 t ha1, applied at the time of pre-puddling tillage); (ii) N120P30K30 (nitrogen, phosphorus and potash @ 120, 30 and 30 kg ha1); (iii) N120P30 (same as in (ii) except that K application was skipped); (iv) N120 (same as in (iii) except that P and K application was skipped) in comparison to the control treatment (without any FYM or inorganic fertilizer). The treatments were allocated in plots of size 8 m 3 m replicated four times in randomized block design (RBD). Whole of P and K and one-third amount of N fertilizer were added at the time of field preparation. The remaining amount of N was applied at 21 and 42 days after transplanting. The decomposed and dried FYM was spread on the soil surface before pre-puddling tillage. The crop was kept submerged continuously for the first 15 days and thereafter irrigated 2 days after complete disappearance of ponded water in the field. The crop was harvested on
25th October 2004 and the grain yield recorded at 14% moisture content. The same field was again pre-irrigated in the last week of October and disked twice at the field capacity moisture content. It was disked and ploughed twice the next day and thereafter planked once. The wheat (cv. PBW343) was sown on 4th November 2004 and the crop was raised as per the recommended practices of Punjab Agricultural University, except fertilization, which was done as per the treatments. The fertilizer treatments in case of wheat were the same as outlined above in rice crop. Same plots received similar treatments during both the crop seasons. The crop was irrigated at 21, 52 and 131 DAS as per the recommended practice of Punjab Agricultural University. The crop was harvested on 15th April 2005 and the grain yield recorded. 2.3. Observations The soil samples for aggregate size distribution were collected at the depths of 0–15, 15–30, 30–45 and 45– 60 cm from each treatment at the harvest of rice and wheat crops. Big clods (40–50 cm diameter) of soil were sampled for the above-mentioned depth and airdried, made to fall from a height of 60–70 cm on a vegetated surface so as to get broken at natural points of cleavage. These were then passed through 8-mm sieve and those retained on 4-mm sieve were used for aggregate analysis by the wet sieving technique as described by Kemper and Rosenau (1986). The undisturbed soil cores in one edge-sharpened galvanized iron (metallic) cylinders of 7.5 cm internal
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5.0 cm I.D. and 4 cm height with perforated bottom and a filter paper disc fixed with a steel ring at the bottom end) for the soil samples drawn at the harvest of rice and wheat crops from the soil at 0–15, 15–30, 30–45 and 45–60 cm depth. Using the particle density of the soil samples, the total porosity of the soil was calculated. The data so obtained for each observation was analyzed statistically using factorials in randomized block design (RBD) as described by Steel and Torrie (1960).
diameter and 7.5 cm height were collected at the harvest of rice and wheat crops with the help of a small hammer and a piece of wood from all the treatments in 0–15, 15– 30, 30–45 and 45–60 cm soil layers. The precautions were taken to reduce the disturbance of soil within the metallic cylinder during sampling, which was done at 10–12% soil moisture content. The soil cores along with the metallic cylinder were excavated with the help of a spade and the extra soil was retained on both sides of excavated cores and carefully preserved in polythene bags. The soil cores were dried in an oven at 105 8C for 24 h to get dry weight of the soil. The ratio of dry weight of soil core and internal volume of the metallic cylinder was expressed as bulk density in Mg m3. The soil organic carbon was determined by Walkley and Black’s titration method (Piper, 1950). The soil organic carbon (SOC) pools were calculated for each treatment separately at depths 0–15, 15–30, 30–45 and 45–60 cm. From mean pool values, carbon sequestration rate was calculated separately for each treatment over control (without fertilization) after 22-year period of experimentation. The maximum water holding capacity (WHC) was calculated with the help of Keen’s box (steel box of
The wet stability of aggregates, expressed in terms of mean weight diameter (MWD), in relation to inorganic fertilizers and FYM is presented in Table 2. The average MWD was highest in the FYM-treated plots both at the harvest of rice (0.237 mm) and wheat (0.249 mm), followed by that in N120P30K30 treatments. The application of balanced fertilizers helped improve the MWD in both rice and wheat. The FYM improved the MWD by 64 and 67% at the end of rice and wheat crops, whereas N120P30K30 increased the MWD by 58 and
Table 2 Mean weight diameter (MWD) (mm) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Table 3 Organic carbon (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Treatments
Treatments
Rice Control FYM N120 N120P30 N120P30K30 Mean
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
0.145 0.506 0.202 0.274 0.379
0.087 0.237 0.153 0.130 0.220
0.060 0.116 0.086 0.118 0.129
0.049 0.088 0.053 0.074 0.083
0.301
0.165
0.102
0.073
0.085 0.237 0.124 0.149 0.203
Mean
Rice Control FYM N120 N120P30 N120P30K30
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
0.30 0.62 0.34 0.38 0.53
0.20 0.34 0.25 0.27 0.30
0.15 0.22 0.17 0.19 0.20
0.09 0.18 0.10 0.10 0.17
0.43
0.27
0.19
0.13
0.19 0.34 0.22 0.24 0.30
LSD (0.05) Fertilization = 0.023 Soil depth = 0.022 Fertilization soil depth = 0.050
0.129 0.524 0.154 0.244 0.309
0.085 0.224 0.114 0.116 0.213
0.064 0.157 0.069 0.096 0.141
0.054 0.092 0.064 0.071 0.088
0.272
0.150
0.105
0.074
LSD (0.05) Fertilization = 0.006 Soil depth = 0.007 Fertilization soil depth = 0.013
3.1. Soil aggregation
Mean
LSD (0.05) Fertilization = 0.009 Soil depth = 0.008 Fertilization soil depth = 0.018 Wheat Control FYM N120 N120P30 N120P30K30
3. Results and discussion
0.083 0.249 0.100 0.132 0.188
Wheat Control FYM N120 N120P30 N120P30K30 Mean
0.29 0.51 0.39 0.44 0.49
0.23 0.34 0.27 0.29 0.31
0.19 0.26 0.22 0.22 0.24
0.11 0.18 0.13 0.15 0.16
0.42
0.29
0.23
0.15
LSD (0.05) Fertilization = 0.029 Soil depth = 0.026 Fertilization soil depth = 0.059
0.21 0.32 0.25 0.28 0.30
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helped increase the organic C content by 44 and 37%, respectively in rice crop (Table 3). The increase was more pronounced in the surface layers. The increased organic C content might be responsible for stabilization of aggregates and hence higher MWD with the application of FYM and inorganic fertilizers.
56%, respectively, from that in control plots. There was significant decrease in MWD with the soil depth. It decreased 0.301 mm in 0–15 cm to 0.165 mm in 15– 30 cm, 0.102 mm in 30–45 cm, to 0.070 mm in 45– 60 cm soil layers in rice. A significant interaction could be observed between the treatments and soil depth in both the crops. The effect of FYM in increasing the MWD decreased with soil depth. At the end of rice harvest, FYM increased MWD by 71, 64, 48 and 44% in 0–15, 15–30, 30–45 and 45–60 cm soil layers, respectively. On the other hand, the correspondence increase in MWD with N120P30K30 was 62, 60, 53 and 41%, respectively. Similar trend could be observed at the end of wheat crop. Since the effect of FYM in increasing MWD was pronounced till the deeper layers, it indicates that apart from direct effect of FYM as a binding agent (Bhushan and Sharma, 2002), it indirectly might have helped in increasing MWD through increased root biomass (mainly root hair) and hence organic matter. Similarly the inorganic fertilizers might have helped in increasing the root biomass than in control plots which ultimately helped in increasing the MWD (Haynes and Naidu, 1998). The addition of FYM and inorganic fertilizers
The soil bulk density recorded at the harvest of rice and wheat (Table 4) shows that FYM helped decrease the bulk density significantly in comparison to that of control plots in all the soil layers (0–60 cm). However, the decrease was more in upper soil layers (0–15 and 15–30 cm) than in lower layers. In N120- and N120P30 plots, the bulk density of all the layers was at par with that in control plots. The balanced use of fertilizers (N120P30K30) significantly decreased bulk density of all the layers from that in control, the decrease being more in upper layers than in lower layers, both after rice and wheat crops. As in MWD, the mean total porosity of soil during rice crop increased significantly with the application of FYM and inorganic fertilizers (Table 5) in both rice and
Table 4 Soil bulk density (Mg m3) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Table 5 Total soil porosity (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system
Treatments
Treatments
Rice Control FYM N120 N120P30 N120P30K30
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
1.69 1.60 1.67 1.65 1.63
1.75 1.69 1.73 1.72 1.70
1.76 1.70 1.74 1.73 1.72
1.75 1.71 1.75 1.74 1.73
Mean
Rice Control FYM N120 N120P30 N120P30K30 Mean
LSD (0.05) Fertilization = 0.05 Soil depth = 0.06 Fertilization soil depth = 0.03 Wheat Control FYM N120 N120P30 N120P30K30
3.2. Soil bulk density and total porosity
1.69 1.58 1.65 1.62 1.60
1.75 1.63 1.68 1.67 1.65
Mean LSD (0.05) Fertilization = 0.06 Soil depth = 0.04 Fertilization soil depth = 0.05
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
32.2 40.5 35.3 36.4 38.7
30.1 36.3 34.7 34.2 35.4
29.5 32.3 30.2 30.4 31.8
27.2 32.5 30.6 30.2 31.6
36.6
34.1
30.8
30.4
29.7 35.4 32.7 32.8 33.4
LSD (0.05) Fertilization = 0.025 Soil depth = NS Fertilization soil depth = 0.058 1.75 1.65 1.72 1.70 1.68
1.75 1.70 1.73 1.72 1.71
Wheat Control FYM N120 N120P30 N120P30K30 Mean
37.1 42.5 38.2 39.3 41.4
32.5 36.3 33.6 34.1 35.4
30.2 34.7 33.4 31.1 33.3
29.1 32.4 31.3 30.2 31.1
39.6
34.4
32.5
30.8
LSD (0.05) Fertilization = 0.033 Soil depth = NS Fertilization soil depth = NS
32.2 36.5 34.1 33.7 35.3
R. Rasool et al. / Soil & Tillage Research 96 (2007) 64–72
wheat crops. The addition of FYM promotes the total porosity of the soils as the microbial decomposition products of organic manures such as polysaccharides and bacterial gums are known to act as soil particle binding agents. These binding agents increase the porosity and decrease the bulk density of the soil (Bhatia and Shukla, 1982) by improving the aggregation. Increase in soil porosity with fertilization has also been reported by Yeoh and Oades (1981), Schjonning et al. (1994) and Prasad and Sinha (2000). The total porosity increased with the application of balanced fertilizers. It decreased with depth, though nonsignificantly in rice. There was significant difference in the effect of FYM and other treatments with depth. In 0–15 cm soil layer, the total porosity increased by 25% with the application of FYM from that in control in rice crop. This difference decreased to 13% in 15–30 cm soil layer. However, in the deeper layers, the difference in total porosity among the treatments was not significant. Similar was the case with N120P30K30 treatment, where the increase in total porosity from that in control decreased with soil depth. Thus, the effect of FYM and inorganic fertilizers in increasing the total soil porosity was more pronounced in the surface soil layers. The higher total porosity of the soil particularly of the surface layer helps in ready exchange of O2 and CO2 between the soil and the atmosphere, thereby, promoting better root growth in the soil. Similar was the trend in wheat crop except that total soil porosity was affected equally in all the soil layers. 3.3. Maximum water holding capacity The average WHC of soil during rice was (16%) higher in FYM plots than in control plots, whereas it was 11% higher in N120P30K30 plots (Table 6). The application of balanced inorganic fertilizers increased the water holding capacity of soils. The WHC of unbalanced fertilizer plots was not significantly different from that in control plots. The higher organic carbon content in FYM-treated plots could be responsible for increasing the WHC of the soil, the difference is being more pronounced in surface soil layers though the balanced application of NPK enhanced the organic carbon restoration probably due to higher root biomass. The application of inorganic fertilizers thus improves the WHC of soil (Singh et al., 2003). The difference in WHC of FYM and inorganic fertilizers treated plots was significant in both rice and wheat crops. It, however, did not vary significantly with soil depth. At the harvest of rice crop, the WHC was 17.3, 15.6, 17.7 and 15.1% higher in FYM treated plots than in control plots in 0–5,
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Table 6 Maximum water holding capacity (%) as affected by inorganic fertilization and FYM treatments under rice–wheat system Treatments
Rice Control FYM N120 N120P30 N120P30K30 Mean
Soil depth (cm)
Mean
0–15
15–30
30–45
45–60
31.6 38.2 32.7 33.4 34.8
30.2 35.9 31.6 32.4 33.8
28.3 34.4 30.7 31.0 32.4
27.5 32.4 29.6 30.8 31.3
34.1
32.8
31.4
30.3
29.4 35.2 31.1 31.9 33.1
LSD (0.05) Fertilization = 1.25 Soil depth = NS Fertilization soil depth = 2.50 Wheat Control FYM N120 N120P30 N120P30K30 Mean
30.6 41.2 34.4 35.8 38.4
29.3 38.4 32.4 33.7 33.7
25.0 34.6 31.8 32.6 32.7
22.7 33.8 29.1 30.1 31.2
36.1
33.5
31.3
29.4
26.9 37.0 31.9 33.0 34.0
LSD (0.05) Fertilization = 1.35 Soil depth = 1.21 Fertilization soil depth = 2.70
15–30, 30–45 and 45–60 cm soil layers, respectively. The corresponding values of increase in case of N120P30K30 were 9.1, 10.6, 12.6 and 12.0%, respectively in the 0–15, 15–30, 30–45 and 45–60 cm soil layer. The higher WHC in the surface layer due to FYM is expected because of its addition in surface layers, whereas in the subsurface layers the increase in WHC could be due to the increased root biomass with FYM or inorganic fertilizers (Singh et al., 2003) and hence organic C. 3.4. SOC pool and C sequestration The SOC pools for different treatments (Table 7) shows that highest C (31.4 Mg ha1) was pooled in FYM-treated plots and lowest (21.3 Mg ha1) in control plots. The N120 plots pooled 19.7% higher SOC than control plots. Addition of P and P + K fertilizers improved SOC pool by 28.6 and 39%, respectively. There was no difference in mean (0–60 cm) SOC pool in FYM- and N120P30K30-plots. The SOC pool decreased significantly with soil depth in all the treatments. Fertilizer or manure application would be expected to increase SOC, because of greater C input associated with enhanced primary production and crop residues returned
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R. Rasool et al. / Soil & Tillage Research 96 (2007) 64–72
Table 7 Soil organic carbon pools (Mg ha1) and carbon sequestration rate as affected by inorganic fertilization and FYM treatments under rice–wheat system Treatments
Soil depth (cm) 0–15
15–30
30–45
45–60
0–60
Control FYM N120 N120P30 N120P30K30
7.35 12.1 9.65 10.7 11.8
6.04 8.31 6.80 7.26 7.67
4.99 6.44 5.68 5.61 6.05
2.89 4.59 3.37 3.87 4.10
21.3 31.4 25.5 27.4 29.6
Mean
10.3
7.22
5.75
3.76
27.0
C sequestration rate (Mg ha1 year1) – 0.31 0.13 0.19 0.26
LSD (0.05) for SOC pools Fertilization = 4.3 Soil depth = 2.1 Fertilization soil depth = NS
to the soil. Parker et al. (2002) reported 7–20% greater organic C in the surface 5 cm of soil in a cotton-rye (Secale cereale L.) cropping system with a poultry litter than with commercial fertilizer application. Application of dairy manure increased SOC by 2.7 Mg C ha1 in a cotton-corn rotation with cover crops (Terra, 2004). The carbon sequestration rate over 32 years of experimentation was maximum (0.31 Mg ha1 year1) in FYM-plots, followed by 0.26 Mg ha1 year1 in N120P30K30-plots, 0.19 Mg ha1 year1 in N120P30 and minimum (0.13 Mg ha1 year1) in N120-plots (Table 7). This shows that balanced fertilization helps in sequestering higher carbon than that sequestered by unbalanced fertilization. Franzluebbers (2005) estimated that the net C offset due to N fertilization could be optimized at 0.24 Mg C ha1 year1 with the application of 108 kg N ha1 year1 assuming a C cost of 1.23 kg C kg1 N N fertilizer for the manufacture, distribution and application of fertilizer N (Izaurralde et al., 1998). The exploitative practices in intensive agriculture viz. removal of plant residues, imbalanced nutrition are mainly responsible for increased carbon emissions from the soils (Lal, 2003). More research is needed urgently to investigate the effect of animal manure application on SOC sequestration, yield potential and quality characteristics and nutrient leaching in rice–wheat system. The widespread availability of dairy manure (FYM) in the region dictates a need for greater understanding of how nutrients can be recycled among agricultural enterprises more effectively to meet production and environmental goals. 3.5. Crop performance The grain yield of rice was significantly higher (49.4%) in FYM-treated plots than in control plots. It
was closely followed by (47%) higher than that in N120P30K30-plots (Table 8). However, there was no significant difference in the grain yield of FYM and N120P30K30-plots. The balanced fertilization improved the grain yield of rice. Similar was the trend in straw yield except that it was non-significantly higher in N120P30K30-plots. The uptake of N, P and K followed the trend as in the grain yield of rice. It was highest in FYM-treated plots, followed by N120P30K30-plots but was significantly lower in the control treatment. Better physical environment coupled with sufficiency of water and nutrients helped in better uptake of water and nutrients and hence the yield of rice. Yang et al. (2004) observed that incorporation of organic residues significantly increased uptake of N, P and K by rice plants and facilitated the allocation and Table 8 Yield and nutrient uptake by rice–wheat system under inorganic fertilization and FYM treatments Treatments
Grain yield (Mg ha1)
Nutrient uptake (kg ha1)
Grain
Straw
N
P
K
Rice Control FYM N120 N120P30 N120P30K30 LSD (0.05)
5.30 7.92 6.85 7.47 7.77 1.60
11.5 20.4 16.0 19.2 21.2 4.12
70.5 105.3 91.1 99.3 103.3
12.2 18.2 15.7 17.2 17.9
14.8 22.2 19.2 20.9 21.7
Wheat Control FYM N120 N120P30 N120P30K30 LSD (0.05)
2.06 4.83 2.99 4.05 4.37 0.72
8.35 15.3 10.6 13.5 13.9 2.52
39.0 105.3 55.7 81.1 93.9
6.40 16.5 9.28 13.8 14.9
10.2 28.0 15.5 21.9 24.5
R. Rasool et al. / Soil & Tillage Research 96 (2007) 64–72
transfer of nutrient elements to the rice ears and grains. Similar trend was observed in the performance of wheat after rice where the FYM-treated plots recorded highest grain (4.83 Mg ha1) and straw (15.3 Mg ha1) yields followed by that in N120P30K30-plots (4.37 and 13.9 Mg ha1, respectively). The uptake of N, P and K by wheat grains was higher in FYM- and N120P30K30plots. Sharma et al. (2003) observed that the addition of Lantana spp. @ 10, 20 and 30 Mg ha1 increased wheat yields by 11, 14 and 20% from that in control, whereas it increased the total (rice + wheat) system productivity by 15, 20 and 26% over controls and at the same time saved NPK fertilizers. The better crop yields of rice and wheat with organic and inorganic balanced fertilization helps improve soil physical environment, pool greater carbon content and better C sequestration in the soils. 4. Conclusions The soil physical properties viz. MWD, total porosity and maximum water holding capacity increased equally with the application of FYM and N120P30K30. The increase in total porosity was more pronounced in the surface layers whereas the MWD increased in the deeper layers as well and water holding capacity was same throughout the profile. The soil bulk density was lower in FYM and N120P30K30 plots than in control plots especially in the surface layers. The FYM and N120P30K30 had similar effect on SOC pool, whereas FYM sequestered more C in FYM plots (0.31 Mg ha1 year1) than in N120P30K30 (0.26 Mg ha1 year1). The application of balanced fertilization increased C sequestration. The uptake of N, P and K and grain yields of both rice and wheat were higher with the application of FYM and N120P30K30. References Acharya, C.L., Bishnoi, S.K., Yaduvanshi, H.S., 1998. Effect of longterm application of fertilizers, and organic and inorganic amendments under continuous cropping on soil physical and chemical properties in an Alfisol. Indian J. Agric. Sci. 58, 509–516. Aggarwal, G.C., Sidhu, A.S., Sekhon, N.K., Sandhu, K.S., Sur, H.S., 1995. Puddling and N management effects on crop response in a rice–wheat cropping system. Soil Till. Res. 36, 129–139. Ali, M.M., 1998. Degradation of paddy soils during the period 1967– 95 in Bangldesh. Ph. D. Thesis, Faculty of Life and Environment Sciences, Shimane University, Matsue 690, Japan. Anderson, S.M., Gantzer, C.J., Brown, J.R., 1990. Soil physical properties after 100 years of continuous cultivation. J. Soil Water Conser. 45, 117–121.
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Barzegar, A.R., Yousefi, A., Daryashenas, A., 2002. The effect of addition of different amounts and types of organic materials on soil physical properties and yield of wheat. Plant Soil 247, 295– 301. Belford, R.K., Klepper, B., Rickman, R.W., 1987. Studies of intact shoot root systems of field grown winter wheat. II. Root and shoot developmental patterns as related to nitrogen fertilizer. Agron. J. 79, 310–319. Benbi, D.K., Biswas, C.R., Bawa, S.S., Kumar, K., 1998. Influence of farmyard manure, inorganic fertilizers and weed control practices on some soil physical properties in a long term experiment. Soil Use Manage. 14, 52–54. Bhatia, K.S., Shukla, K.K., 1982. Effect of continuous application of fertilizers and manure on some physical properties of eroded alluvial soil. J. Indian Soc. Soil Sci. 30, 33–36. Bhuiyan, N.I., 1992. Intensive cropping and soil nutrient balance. In: A key note paper presented at the international conference on ‘‘Improving soil management for intensive cropping in the tropics and subtropics’’, BARC, Dhaka, Bangladesh, December 1–3. Bhushan, L., Sharma, P.K., 2002. Long-term effects of lantana (Lantana spp. L.) residue additions on soil physical properties under rice–wheat cropping I. Soil consistency, surface cracking and clod formation. Soil Till. Res. 65, 157–167. Brar, S.P.S., Rekhi, R.S., Benbi, D.K., 1997. Long term effect of N, P, K and Zn application on crop yield and soil properties in a maize what system. In: Proceedings of 3rd Agricultural Science Congress PAU, Ludhiana, March 12–15, p. 1997. Brown, S.C., Keatinge, J.D.H., Gregory, P.J., Cooper, P.J.M., 1987. Effect of fertilizer, variety and location on barley production under rainfed condition in northern Syria. I. Root and shoot growth. Field Crops Res. 16, 53–66. Dexter, A.R., 1988. Advances in characterization of soil structure. Soil Till. Res. 11, 199–238. Ekwue, E.I., 1992. Effect of organic and fertilizer treatments on soil physical properties and erodibility. Soil Till Res. 22, 199–209. El-Shakweer, M.H.A., El-Sayad, E.A., Ewees, M.S.A., 1998. Soil and plant analysis as a guide for interpretation of the improvement efficiency of organic conditioners added to different soil in Egypt. Comm. Soil Sci. Plant Anal. 29, 2067–2088. Franzluebbers, A.J., 2005. Soil organic carbon sequestration and agricultural GHG emissions in the southeastern USA. Soil Till. Res. 83, 120–147. Haynes, R.J., Naidu, R., 1998. Influence of lime, fertilizer and manure applications on soil organic matter content and soil physical conditions: A review. Nutr. Cycl. Agroecosyst. 51, 123–137. Izaurralde, R.C., McGill, W.B., Bryden, A., Graham, S., Ward, M., Dickey, P., 1998. Scientific challenges in developing a plan to predict and verify C storage in Canadian Prairie soils. In: Lal, R. (Ed.), Management of Carbon Sequestration in Soil. CRC Press, Broca, Raton, FL, pp. 443–446. Kemper, W.D., Rosenau, R.C., 1986. Aggregate stability and size distribution. In: Klute, A. (Ed.), Methods of Soil Analysis. I. Agronomy Monograph No. 9. second ed. pp. 771–798. Kukal, S.S., Aggarwal, G.C., 2003a. Puddling depth and intensity effects in rice–wheat system on a sandy loam soil. I. Development of subsurface compaction. Soil Till. Res. 72, 1–8. Kukal, S.S., Aggarwal, G.C., 2003b. Puddling depth and intensity effects in rice–wheat system on a sandy loam soil. II. Water use and crop performance. Soil Till. Res. 74, 37–45. Lal, R., 2003. Soil erosion and the global carbon budget. Environ. Intern. 29, 437–450.
72
R. Rasool et al. / Soil & Tillage Research 96 (2007) 64–72
Mokwunge, A.U., deJager, A., Smaling, E.M.A., 1996. Pestoring and maintaining the productivity of west African soil: key to sustainable development. In: Miscellaneous Fertilizers Studies No. 14. Parker, M.A., Nyakatawa, E.Z., Reddy, K.C., Reeves, D.W., 2002. Soil carbon and nitrogen as influenced by tillage and poultry litter in north Alabama. In: van Santen, E. (Ed.), Making Conservation Tillage Conventional: BUILDING a FUture on 25 years of Research. Proceedings of 25th Annual Southern Conservation Tillage Conference Sustainable Agriculture, Auburn, AL, 24– 26 June 2002, pp. 283–287. Pernes-Debuyser, A., Tessier, D., 2004. Soil physical properties affected by long-term fertilization. Eur. J. Soil Sci. 55, 505–512. Piper, C.S., 1950. Soil and Plant Analysis. International Science Publishers, New York, USA. Prasad, B., Sinha, S.K., 2000. Long-term effects of fertilizers and organic manures on crop yields, nutrient balance and soil properties in rice–wheat cropping system in Bihar. In: Abrol, I.P., Bronson, K.f., Duxbury, J.M., Gupta, R.K. (Eds.), Long term soil fertility experiments in rice–wheat cropping systems. Rice– Wheat Consortium Paper Series 6. New Delhi, India: Rice– Wheat Consortium for the Indo–Gangetic Plains. pp. 105–119. Sarkar, S., Singh, S.R., Singh, R.P., 2003. The effect of organic and inorganic fertilizers on soil physical condition and the productivity of a rice–wheat cropping sequence in India. J. Agric. Sci. 140, 419–425. Saunders, D.A., 1991. Report of an on farm survey: Jessore and Kustia: Farmer’s practices and perceptions. Monograph No. 8. Wheat Research Center, BARI, Dinajpur, Bangladesh. Schjonning, P., Christensen, B.T., Carstensen, B., 1994. Physical and chemical properties of a sandy loam receiving animal manure, mineral fertilizer or no fertilizer for 90 years. Eur. J. Soil Sci. 45, 257–268.
Schjonning, P., Iversen, B.V., Munkholm, L.J., Labouriau, R., Jacobsen, O.H., 2005. Pore characteristics and hydraulic properties of a sandy loam supplied for a century with either animal manure of mineral fertilizers. Soil Use Manage. 21, 265–275. Sharma, P.K., Bhushan, L., 2001. Physical characterization of a soil amended with organic residues in a rice–wheat cropping system using a single value soil physical index. Soil Till. Res. 60, 143– 152. Sharma, P.K., Ladha, J.K., Verma, T.S., Bhagat, R.M., Padre, A.T., 2003. Rice–wheat productivity and nutrient status in a lantana(Lantana spp.) amended soil. Biol. Fertil. Soils 37, 108–114. Singh, M.V., Manna, M.C., Wanjari, R.H., Singh, Y.V., Rajput, G.S., 2003. Comprehensive report, NATP-RRPS 19—organic pools and dynamics in relation to land use, tillage and agronomic practices for maintenance of soil fertility. IISS, Bhopal, pp. 1–92. Smaling, E.M.A., Nandwa, S.M., Janseen, B.H., 1997. Soil fertility in African is at stake. In: Buresh, R.J., Sanchez, P.A., Calhoum, F. (Eds.), Replenishing Soil Fertility in African. SSSA special publication No. 51, Wisconsin, USA, pp. 47–61. Steel, R.G.D., Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, pp. 232–251. Terra, J.A., 2004. Soil management and landscape variability impacts on field scale cotton and corn productivity. Ph.D. Dissertation, Auburn University, Auburn, AL. Yang, C., Yang, L., Yang, Y., Ouyang, Z., 2004. Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils. Agric. Water Manage. 70, 67– 81. Yeoh, N.S., Oades, J.M., 1981. Properties of soils and clays after acid treatment. II. Urrbrae fine sandy loam. Aust. J. Soil Res. 19, 159– 166.