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Organic resource management: Impacts on soil aggregate stability and other soil physico-chemical properties
Agriculture, Ecosystems and Environment 148 (2012) 22–28
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Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee
Organic resource management: Impacts on soil aggregate stability and other soil physico-chemical properties Alidad Karami a , Mehdi Homaee a,∗ , Sadegh Afzalinia b , Hassan Ruhipour c , Sanaz Basirat d a
Department of Soil Science, Faculty of Agriculture, Tarbiat Modares University, Tehran, P.O. Box 14115-336, Iran Department of Agricultural Engineering Research, Fars Research Center for Agriculture and Natural Resources, P.O. Box 73415-111, Shiraz, Iran Hassan Ruhipour, Research Institute of Forests and Rangelands, Tehran, Iran d Faculty of Agriculture, Azad University of Shiraz, P.O. Box 7189815614, Shiraz, Iran b c
a r t i c l e
i n f o
Article history: Received 20 April 2011 Received in revised form 18 October 2011 Accepted 25 October 2011 Available online 15 December 2011 Keywords: Aggregate stability Bulk density Manure Organic matter
a b s t r a c t Effects of different types and amounts of organic matters (OM) on the soil aggregate stability indices as well as some soil properties were investigated. This study was conducted in the form of a split-plot experimental design with OM sources (sheep manure, cow manure, rice husk, finely chopped reeds, wheat straw, licorice (root) dregs) as main plot factors, and OM application rates (5, 15, and 25 ton ha−1 ) as sub-plot factors. Mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregate (WSA) were measured using both wet and dry sieving methods. The soil aggregate percents (SAP) > 0.84 mm and soil fragment percents (SFP) < 0.42 mm, water stable aggregate (WSA) > 0.5, WSA > 0.25 mm, soil bulk density (BD), and soil water infiltration were also measured in this study. Results showed that application of OM sources had positive effects on the soil MWD and GMD. The GMD and SAP > 0.84 mm increased following application of sheep and cow manure. The SAP > 0.84 mm, MWD, and GMD showed increasing trend from the beginning of the sowing stage to the end of the growing season. However, the SFP < 0.42 mm decreased for the same period. Applying all rates of OM increased the soil aggregate stability compared to the control treatment. The maximum values of MWD, GMD, WSA > 0.5, and WSA > 0.25 were obtained from 25 ton ha−1 OM application. In those plots that received cow manure, wheat straw, sheep manure, and rice husk, the WSA > 0.5 mm were higher than that of the control treatment. Application of OM increased OC, P, K, Mn, and Fe in the soil, while pH decreased with OM application. Applying different sources of OM decreased soil bulk density (BD) and increased infiltration rate. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Unfortunately, most soils in arid and semi-arid regions contain less than 1% organic matter. Soil organic matters restoration has beneficial effects on soil conservation, aggregate stability, soil physical properties improvement and attributes on the plant growth and crop production. Aggregate stability tests are necessary for a reliable description and ranking of soil behavior under water, wind, and field management effects (Amezketa, 1999). Soil organic matter loss is high in most soils of Iran due to high solar radiation, low soil moisture, and long-term intensive cropping. Soil organic matter may be lost rapidly under intensive cropping systems because of increased rate of organic carbon mineralization following tillage in addition to erosion losses and decreased OM returns through crop removal (Gregorich et al., 2001). Most soil scientists acknowledge
∗ Corresponding author. Tel.: +98 2148292280; fax: +98 2144196524; mobile: +98 9121483992. E-mail address: [email protected] (M. Homaee). 0167-8809/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2011.10.021
that soil organic matter conservation has positive effects on the soil properties (Chirinda et al., 2010; Hargreaves et al., 2008; Papini et al., 2011). These positive effects include higher water retention, higher cation exchange capacity, ability to retain nutrients within the root zone, greater buffering capacity against pH change, ability to chelate and form complex ions, contribution to soil structure, formation of stable aggregates, sustenance of soil biological activities, and biodiversity by providing food and habitat for soil animals and microorganisms (Degens et al., 2000). In agricultural systems, conserving soil organic carbon has been recognized as a strategy to reduce soil degradation. On the other hand, residue management, artificial addition of OM sources, to the soil and clay mineral, and sesquioxide of soil are the most important factors in the soil structural development and soil aggregation improvement (Bhattacharyya et al., 2009; Wagner et al., 2007). Although, it is practically impossible to alter the clay mineral and sesquioxide content of soil for the large areas, increasing the SOM content in the field is feasible (Aulakh et al., 2001). Topsoil is a huge terrestrial reservoir of carbon which has a modifying effect on the carbon dioxide concentrations in the
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atmosphere and can thus influence climate warming and environmental processes at a global scale (Barreto et al., 2009). Soil organic matter is a big source of nitrogen (N) and over 90% of N in soils is in organic form (Batjes, 1996). Application of sludge could increase the soil organic carbon and provide hydrolyzable carbohydrate content and greater structural stability (Ojeda et al., 2008). Well-established strategies for increasing SOM contents in agricultural production systems include the production and incorporation of green manure crops (Aulakh et al., 2001; Bejbaruha et al., 2009; Gerzabek et al., 2001), application of livestock manure (Gerzabek et al., 2001), and crop residue incorporation into the topsoil, with a subsequent increase in mineralization and microbial biomass (Hargreaves et al., 2008). The incorporation of barley straw was reported to be most effective for water-stable aggregates development in the soils with 34% and 38% clay (Wagner et al., 2007). Applying 3.1 and 12.4 ton ha−1 straw to the soil could also increase soil aggregation by about 100% and 250%, respectively (Wagner et al., 2007). Tillage has different effects on the soil ecosystem including soil carbon and nitrogen reduction, soil structure degradation, microbial community alteration, and consequently microbial biomass reduction (DuPont et al., 2010). Tejada et al. (2006) found that organic matter acted as a cementing factor necessary for flocculating soil particles and forming stable aggregates. Tejada et al. (2007) showed that composted OM sources had a positive effect on the soil properties such as structural stability, microbial biomass, soil respiration, urease, dehydrogenase, BBA-protease, aˆ-glucosidase, soil phosphatase activities, and bulk density. They also reported that organic by-products resulting from industrial processes represented an important source of nutrients especially for organic fertilization. The improvement of soil structure through addition of OM will lead to a high degree of aggregation and a large portion of soil aggregates in the size range of 1–10 mm, which remain stable when wetted (Tisdall and Oades, 1982). Soils with good structure, generally provides suitable soil physical properties including a high water-holding capacity, moderate saturated hydraulic conductivity, and sufficient aeration for plant establishment and growth (Riahi et al., 2009; Tisdall and Oades, 1982). Depending on the extent of disruption caused by agricultural practices such as tillage and incorporation of organic matter into soil, aggregates can provide physical protection of SOM and retard its decomposition (Kravchenko and Thelen, 2009; Pulleman and Marinissen, 2004). Furthermore, a favorable soil structure greatly increases soil resistance to both wind and water erosion (Barthes et al., 2000; Bilalis and Karamanos, 2010). Hydrogen bonding between polar groups of the organic molecules and adsorbed water molecules or oxygen of the silicate surface may contribute to greater aggregate stability. Consequently, the amount of mechanical stress that a soil can withstand will generally be increased by the presence of OM (Zhang et al., 2005). Maintaining soil quality at the surface is necessary to have a safe soil and adequate production. In this sense, the protection and increasing soil OM is essential to keep adequate levels of organic C (Lpez-Garrido et al., 2011; Ryan et al., 2006). Reduced aggregate stability may decrease rate of water infiltration and crop production and increase slaking and crusting, and runoff erosion. Applying OM can also improve water storage, sources of biodiversity, retention of contaminants, faster decomposition of wastes, and erosion control (Ahmad et al., 2008). Saha and Mishra (2009) concluded that annual organic manure application or organic residue conservation may mitigate the negative effect of puddling and related properties; therefore, could contribute to the sustainability of the wetland rice ecosystem. In our region, high solar radiation, arid climate condition, excessive use of chemical fertilizers, residue removal, and improper field
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management decrease soil OC and soil quality attributes. Losses of soil OM are reflected in adverse modifications in soil biological, chemical and physical properties, such as reduced soil biodiversity, soil buffering capacity, cation exchange capacity, nutrient availability, water infiltration, and increased destruction of soil structure, soil compaction and erosion. Because of beneficial role of OM on soil quality, as an effective soil component in stabilizing soil structure and controlling soil resistance to erosion, and its stabilizing role on the aggregation and aggregate stability, this study was conducted to assess the effect of different sources and amounts of OM on the soil aggregate stability and some related soil physico-chemical properties at field scale. Therefore, an understanding of the effects of applying different OM sources and rates on aggregation and aggregate stability, and other soil physico-chemical properties on a large scale in arid and semi-arid regions is novel in this research. 2. Materials and methods 2.1. Experimental design The study was conducted in Zarghan area located at southern Iran with an average annual rainfall of 330 mm, minimum longterm temperature of 7.4 ◦ C, and maximum temperature of 24.7 ◦ C. A field experiment was conducted in a split-plot design with OM sources (sheep manure (SM), cow manure (CM), rice husk (RH), finely chopped reeds (FCR) or phragmites-australis (cav.), wheat straw (WS), licorice (root) dregs (LD), and a treatment without applying any sources of OM or control treatment (CT)) as main plots and OM application rates (5, 15, and 25 ton ha−1 ) as sub-plots with three replications in three consecutive years. The applied organic amendments were loosely mixed with the topsoil. The measured indices consisted of soil aggregate mean weight diameter (MWD), geometric mean weight diameter of soil aggregates (GMD), SAP > 0.84 and SFP < 0.42 mm, soil bulk density (BD), water infiltration rate, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm. Some soil properties such as soil moisture content (SMC), pH, EC, OC, Pavailable , Kavailable , Mn, Fe, Ca + Mg, Na, and sodium absorption ratio (SAR) under different OM applications were also measured. 2.2. Soil sampling and analyses To determine the soil aggregate MWD, samples were taken at three stages; before applying the OM and before planting, mid plant growing period (11 weeks after planting), and after plant harvesting. A metal box of 170 mm × 170 mm × 50 mm was used to take the samples. The samples were delivered to a laboratory to separate plant roots and residues. The aggregate stability was measured using both wet and dry sieving methods. In dry sieving method, soil samples were divided into seven different classes using a standard set of dry sieves. These classes were consisted of soil aggregates and fragments < 0.42 mm, 0.42–0.84 mm, 0.84–2 mm, 2–4 mm, 4–6.4 mm, 6.4–12.7 mm, and 12.7–38 mm. SAP > 0.84 and SFP < 0.42 mm, MWD, and GMD were calculated to determine soil erodibility against wind using dry sieving method. The MWD and GMD were calculated using the following equation (Oguike and Mbagwu, 2009): MWD =
n
X¯ i Wi
(1)
i=1
where X¯ i is the mean diameter of aggregates over each sieve size, Wi is weight of the aggregates in that size range as a fraction of total dry weight of the sample analyzed, and n is number of sieves. This parameter gives the aggregate size distribution.
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Table 1 Some chemical properties of different OM sources used in the study. OM sources
EC (dS m−1 )
pH
T.N.V. (%)
OC (%)
P (mg kg−1 )
K (mg kg−1 )
Fe (mg kg−1 )
Zn (mg kg−1 )
Cu (mg kg−1 )
Mn (mg kg−1 )
LD RH FCR WS SM CM
0.56 1.07 1.77 1.77 4.08 4.23
7.7 6.6 4.8 5.6 7.2 8.7
4.50 1.25 0.50 8.25 6.00 13.25
54.10 44.34 52.97 38.74 45.08 40.57
0.07 0.05 0.07 0.12 0.72 0.7
0.24 0.52 0.53 1.49 2.71 3.22
3737 519 466 529 2500 3866
44.35 31.95 12.40 27.30 62.35 70.60
20.1 2.6 3.6 10.3 19.6 21.2
62.35 103.25 229.05 193.30 145.85 211.85
LD: licorice (root) dregs, RH: rice husk, FCR: finely chopped reeds, WS: wheat straw, SM: sheep manure, CM: cow manure.
The geometric mean diameter of aggregates was calculated based on:
n W log X¯ i i=1 i GMD = exp n n
i=1
Wi
(2)
W is the total weight of aggregates. where i=1 i The water stable aggregate index which accounts for aggregate stability was calculated using the following equation: WSA =
Mr × 100 Mt
(3)
where Mr is mass of resistant aggregates and Mt is the total mass of wet sieved soil. To determine aggregate stability and related size distribution at wet condition, a wet sieving (2–4 mm mesh sieve) method was used with 50 g soil samples. Consequently, six sieves having 0.075, 0.106, 0.25, 0.5, 1, and 2 mm mesh diameter were used. Measurement of aggregate size distribution was accomplished by shaking the sieves for 10 min. The weight of soil on each sieve, total soil weight, and ratio of aggregate weights on each sieve to the total soil weights were then calculated. The soil bulk density was determined using core sampling method at the soil depth ranges of 0–15, 15–30, and 30–45 cm. The infiltration rate in the experimental plots was measured using the double rings method. Different physical and empirical models were tested and the Kostiakov model (Kostiakov, 1932) with following form was best fitted to the obtained experimental data: I = at b
(4)
i = bat (b−1)
(5)
where I (L) is cumulative infiltration, t (T) is time, i (L T−1 ) is infiltration rate, and a and b are empirical constants. The nutrient element contents of different OM sources including P, K, Zn, Cu, and Mn were measured. Soil organic carbon and available forms of P, K, Na, Mn, and Fe under influence of different OM sources were also measured in this research using standard plant and soil analysis methods (Waling et al., 1989).
contained the highest amount of Mn concentration and LD had the highest amount of OC. The applied cow manure had the maximum K, Fe, Zn, Cu, T.N.V., EC, and pH. The maximum P concentration was related to the sheep manure. Results also indicated that OM sources had significant influence on the MWD and GMD so that the largest MWD value was obtained from RH application and the lowest MWD value was related to CM application. However, there was no significant difference between MWD value obtained from RH, WS, FCR, LD, CT, and SM applications (Fig. 1). The data presented in Table 2 indicated that application of OM sources had a significant effect on WSA > 0.5, WSA > 0.25, WSA > 0.106, SFP < 0.42, and SAP > 0.84 mm indices. So that, the highest WSA > 0.5 mm was obtained from the application of wheat straw, licorice (root) dregs, and rice husk. The minimum value of this index belonged to the cow manure. The maximum and minimum values of WSA > 0.25 and WSA > 0.106 mm were obtained from the applied cow manure and finely chopped reeds application, respectively. Meanwhile, the trend of mean soil fragments < 0.42 mm approximately contradicted SAP > 0.84 mm. The maximum value of SAP > 0.84 mm and the minimum amount of SFP < 0.42 mm were related to the sheep manure. The maximum MWD and GMD obtained values from the dry sieving method belonged to the sheep manure (Fig. 2). The obtained mean values of MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm under different organic matter amounts are presented in Table 3. The data presented in this table indicated that the soil MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm increased by increasing the applied OM quantity, so that the maximum MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm values were obtained from the maximum amount of OM application (25 ton ha−1 ). Although these results indicate that the OM rate had a significant influence on the stable aggregates, there was no significant difference between the stable aggregates on the sieve with 0.106 mm mesh under different amounts of OM application. By increasing the amount of applied OM, the soil BD was signif-
2.3. Statistical analyses The collected data were then analyzed using SAS software (SAS Institute, Cary, NC). The independent variables consisted of OM sources and rates, and the dependent variables were considered to be MWD, GMD, SAP > 0.84 mm, SFP < 0.42 mm, (BD), water infiltration rate, WSA > 0.5, WSA > 0.25, WSA > 0.106 mm, soil moisture content (SMC), organic carbon, P, K, Mn, Fe, Ca + Mg, SAR, and Na. The obtained mean values were compared using the Duncan’s multiple range tests at 5% and 1% levels of significance. 3. Results Results of nutrient contents of different OM sources are presented in Table 1. These results show that the finely chopped reeds
Fig. 1. Comparison of different OM sources for the mean MWD and GMD values obtained from wet sieve set method. LD: licorice (root) dregs, RH: rice husk, FCR: finely chopped reeds, WS: wheat straw, SM: sheep manure, CM: cow manure, CT: control treatment.
A. Karami et al. / Agriculture, Ecosystems and Environment 148 (2012) 22–28
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Table 2 Mean values of WSA > 0.5, WSA > 0.25, WSA > 0.106, SFP < 0.42, and SAP > 0.84 mm under application of different OM sources. OM sources
WSA > 0.5 (%)
WSA > 0.25 (%)
WSA > 0.106 (%)
SFP < 0.42 (%)
SAP > 0.84 (%)
WS LD RH FCR CT SM CM
36.86A* 36.75A* 36.40A* 34.76AB* 33.72AB* 33.66AB* 29.68B*
83.86AB* 83.01AB* 85.60AB* 78.14B* 82.81AB* 84.64AB* 87.94A*
96.07A* 94.38AB* 95.94A* 93.41B* 94.88AB* 95.95A* 96.46A*
14.83A** 16.08A** 15.26A** 15.57A** 15.02A** 12.05B** 13.54AB**
72.53BC** 70.88C** 72.45BC** 72.40BC** 72.99BC** 77.55A** 75.13AB**
WSA: water stable aggregate, SFP: soil fragment percent, SAP: soil aggregate percent, CT: control treatment. * Significant at 5%. ** Significant at 1%. Table 3 The obtained mean values of MWD, GMD, BD, SMC, OC, P, K, Mn and water stable aggregates over 0.5, 0.25, and 0.106 mm under different amount of organic matter applications. OM (ton ha−1 )
MWD (mm)
GMD (mm)
WSA > 0.5 (%)
WSA > 0.25 (%)
WSA > 0.106 (%)
BD (g cm−3 )
SMC (%)
OC (%)
Pavailable (mg kg−1 )
Kavailable (mg kg−1 )
Mn (mg kg−1 )
25 15 5
0.93A** 0.81B** 0.83B**
0.79A** 0.75B** 0.74B**
37.29A* 33.04B* 33.31B*
87.15A* 83.63B* 80.37B*
87.15A* 95.25A* 94.76A*
1.20B* 1.23AB* 1.24A*
30A** 27B** 26B**
1.13A** 1.04A** 0.90B**
18.33A* 14.26B* 14.7AB*
470.6A** 436.0B** 432.4B**
21.21A** 20.63A** 18.42B**
BD: bulk density, SMC: soil moisture content OC: organic carbon.
Fig. 2. The influence of different organic matter sources on the mean MWD and GMD obtained from dry sieving method.
icantly reduced and soil moisture retention increased. The soil OC, P, K, and Mn concentrations also increased by increasing OM rates. So that, their maximum amounts were obtained from the treatment with 25 ton ha−1 OM application. The results presented in Table 4 indicated that MWD and GMD increased from the beginning to the end of the growth season. The variation of bulk density, soil moisture content (SMC), organic carbon (OC), P(available) , K(available) , Mn, and Fe concentration under different OM sources applied are presented in Table 5. In spite of lack of difference between the bulk densities under different OM sources, applying finely chopped reeds and the control treatment (without OM) provided the minimum and the maximum bulk density values, respectively. The data presented in Table 5 showed that all the applied OM sources increased the soil OC in such a way that applying licorice (root) dregs had the highest and the control treatment had the lowest amount of OC. The maximum soil phosphorus content was obtained from the applied cow manure, while applying sheep manure had the second place. All the OM sources used increased soil potassium so that applying cow manure had the most significant influence. The soil Mn concentration increased with applying different OM sources; therefore, the control treatment had the minimum amount of soil Mn. Since the licorice (root) dregs treatment
Table 4 Comparison of means MWD and GMD, SFP < 0.42 and SAP > 0.84 mm obtained from dry sieving method at different stages of cultivation. Sampling time
MWD (mm)
GMD (mm)
SFP < 0.42 (%)
SAP > 0.84 (%)
Beginning of cultivation season Middle of cultivation season End of cultivation season
6.51C* 7.65B* 8.77A*
1.49C* 1.61B* 1.76A*
16.76A** 14.62B** 12.48C**
69.89C** 73.42B** 76.95A**
Table 5 Comparison of mean soil bulk density, moisture content, OC, Ca + Mg, SAR, Na+, P, K, Mn, and Fe under application of different OM sources. OM sources
BD (g cm−3 )
SMC (%)
OC (%)
Ca + Mg (%)
SAR
Na+ (mg kg−1 )
Pavailable (mg kg−1 )
Kavailable (mg kg−1 )
Mn (mg kg−1 )
Fe (mg kg−1 )
LD RH CM FCR WS SM CT
1.25A* 1.23A* 1.20A* 1.19A* 1.21A* 1.21A* 1.27A*
31AB* 33A* 26BCD* 25CD* 30ABC* 26BCD* 24D*
1.5A** 1.1B** 1.1B** 1.0B** 0.95B** 0.95B** 0.74C**
8.4Ans 8.5Ans 6.9Ans 8.6Ans 9.2Ans 7.1Ans 6.9Ans
2.35Ans 2.05Ans 2.05Ans 2.26Ans 1.88Ans 2.00Ans 2.34Ans
4.62Ans 4.15Ans 3.78Ans 4.72Ans 4.04Ans 3.78Ans 4.23Ans
10.73C** 9.32C** 34.83A** 9.91C** 10.10C** 23.26B** 12.10C**
402.4C** 443.6BC** 530.9A** 433.6BC** 447.1BC** 478.0AB** 388.9C**
21.19A** 22.19A** 20.47AB** 20.50AB** 20.98A** 18.92AB** 16.33B**
14.35A** 8.29D** 12.74B** 9.94C** 11.79B** 12.25B** 12.35B**
SAR: sodium adsorption ratio.
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contained a large amount of Fe, this treatment provided a soil with the maximum amount of Fe. Although different OM sources had no significant influence on Ca + Mg, sodium adsorption ratio (SAR), and Na concentration, they increased soil Ca and Mg and decreased the SAR leading to a positive effect on the particle coagulation and aggregation. These results are very important for application of OM sources such as cow manure that are saline. Applying different OM sources had positive effect on the soil infiltration rate and a and b parameters of Kostiakov model. Applying different OM sources also significantly increased the infiltration rate. This can be attributed to the positive effects of organic matter on the aggregation and enhancement of soil physical properties (data not shown).
4. Discussion Results of this study demonstrated that application of OM sources had positive effects on the soil physico-chemical properties. On the other hand, there are Great Plains at south Iran with intensive cultivation systems and poor soil management strategies. Therefore, residual management is very important for preserving natural ecosystems (De Bona et al., 2008). Another problem for this area is conventional tillage that reduces the fungal biomass and destroys the aggregates and organic matter (Mele and Crowley, 2008) which prompts deterioration of soil hydrological properties. The obtained results indicated that components of applied OM sources were very different (Table 1). These variations were related to nature and characteristics of OM types. Accordingly, the highest EC, pH, T.N.V., K, Fe, Zn, Cu, and Mn values were belonged to cow manure, while the lowest values belonged to LD, FCR, FCR, RH, FCR, FCR, RH, and LD, respectively. These results indicated that although cow manure is rich of nutrient elements, its application has limitation particularly in arid and semi-arid regions due to salinity. On the other hand, the lowest pH value in FCR is very valuable for calcareous soils that are dominant soil formations in arid and semiarid regions. Practically, the lowest value of EC and highest value of OC in LD are very important factors for OM applications in arid and semi-arid regions. The obtained results also indicated that the MWD, GMD, and SAP > 0.84 mm increased following application of sheep and cow manure. Results of similar field trial showed that long-term manure application promoted the formation of soil macro aggregates and increased aggregate stability (Li et al., 2010). Therefore, one may conclude that the applied sheep and cow manure has generally positive effects on the soil aggregation. The MWD, GMD, and the SAP > 0.84 mm had an increasing trend from the beginning of the sowing stage up to end of the growth season. The soil fragment percents < 0.42 mm decreased as time passed by. This observation describes the fact that increasing decomposition of OM and development of plant roots enhanced both aggregation and aggregate stability. At the end of cultivation season, the SAP > 0.84 mm significantly increased, while SFP < 0.42 mm was reduced. These results indicated that during the plant growth period, both decomposition of applied OM and root development acted as two positive factors influencing aggregation. Tillage operation stimulates the oxidation of SOC, increases residue incorporation into soil, fragments macro-aggregates, and increases surface area for soil microbial activity and decomposing the organic matter which improves soil physical condition (Aulakh et al., 1991; Coppens et al., 2007; Fontaine et al., 2007). This improved soil physical condition could accelerate the decomposing process of the incorporated OM sources and lead to the soil aggregation. The MWD maximum value was obtained from the highest amount of applied organic matter. The soil aggregate stability
increased by application of rice husk, wheat straw, finely chopped reeds, and licorice (root) dregs compared to the control treatment. The highest values of MWD, GMD, WSA > 0.5, WSA > 0.25 mm, SMC, P, K, and Mn were obtained from applying 25 ton ha−1 organic matter. These results indicated that application of OM improved soil physico-chemical properties. It was interesting that the most water stable aggregates remained on the sieves with larger mesh. The WSA > 0.5 mm of the treatments with application of cow manure, wheat straw, sheep manure, and rice husk was larger than that of the control treatment. In this context, Huang et al. (2010) concluded that the positive trends in corn yield and soil productivity treatments with manure application are attributed mainly to the improvement in soil quality. Improved soil aggregation and structure could benefit the crop growth through stimulating root distribution and uptake of water and nutrients (Pachepsky and Rawls, 2003; Bronick and Lal, 2005). In the arid and semi-arid climate, with conventional soil management, deep ploughing brings the material poor in organic matter to the topsoil and applying inorganic fertilizers accelerates humus and organic residues decomposition and consequently reduces aggregate stability (Chirinda et al., 2010). The increase in aggregate stability likely enhances the soil resistance to erosion which is a major threat for crop production and agricultural sustainability (Zhang and Xu, 2005). Therefore, application of organic matter can improve crop yield, soil fertility, and soil physical properties (Naylor et al., 2005; Ju et al., 2006; Li et al., 2010). Intensive cultivation of agro-ecosystems with removed or burned residue has led to loss of soil organic carbon. Therefore, adoption of proper management practices has been suggested to be an effective way to increase the soil quality (Smith, 2004). Application of OM increased the OC, P, K, Mn, and Fe concentrations in the soil and decreased soil pH. Under organic management, deliberate attempts are made to increase soil organic carbon (SOC) levels and enhance nutrient cycling through application of manure and other OM sources (Olesen et al., 2007). Our results indicated that application of OM enhanced the soil fertility status. Using different OM sources increased the soil water infiltration and decreased the soil bulk density. The obtained cumulative infiltration data from application of each OM sources had significant difference with that of CT, such that the largest and lowest cumulative infiltration values were obtained from WS application and CT, respectively (data not shown). These findings are in concurrence with what has been reported by previous investigators. For instance Albiach et al. (2001) reported that application of the organic matter has a positive effect on aggregation, infiltration increases and soil erosion decreases (Ojeda et al., 2003). Khormali et al. (2009) found out that following of deforestation, as a result of considerable losses of organic carbon and breakdown of aggregates, MWD and soil infiltration rate decreased and BD increased. Aggregation is a soil quality indicator that is positively related to the physical protection of organic matter, improved water infiltration, and reduced soil erosion (Rhoton et al., 2002). Mele and Crowley (2008) pointed out that soil aggregate formation leads to better infiltration and organic matter accumulation. On the other hand, application of OM improved aggregation and aggregate stability. These results are in good agreement with those obtained by Bayu et al. (2005) and Verkler et al. (2009). Furthermore, Papini et al. (2011) reported that the organic matter itself enhanced soil resistance to compaction through several mechanisms (strengthening of binding forces among particles and aggregates and increasing elasticity of aggregates under compression) and provided a higher porosity and lower soil bulk density. Different OM sources also significantly increased soil water content and soil moisture capacity. Luo et al. (2010) reported that double cropping per year, can lead to more production of residues and roots than single cropping;
A. Karami et al. / Agriculture, Ecosystems and Environment 148 (2012) 22–28
therefore, double cropping system increases soil carbon stock, reduces soil erosion, and improves soil structure and nutrient cycling. Contrary to this report, in our studied region the annual double cropping can lead to residue removing or burning. Consequently, double cropping in our condition decreases soil carbon, increases soil erosion, and adversely affects the soil structure as well as nutrient cycling. Our observation implied that high solar radiation, residue removal, and unfavorable field management were main factors influencing on the soil quality attributes. Other researchers (Assis et al., 2010; Lemke et al., 2010) have shown that these factors influence soil quality (e.g., N and C mineralization, light fraction organic matter, microbial biomass carbon and soil aggregate stability). 5. Conclusions Application of different OM sources had significant influences on soil MWD, GMD, and SAP > 0.84, such that these indices increased with sheep and cow manure applications. Soil MWD, GMD, WSA > 0.5, and WSA > 0.25 increased by increasing OM application rates, such that the maximum values of these parameters were attained with maximum rate of OM application (25 ton ha−1 ). Soil water retention increased by increasing OM application rates, while soil bulk density decreases by increasing OM application rate. Positive effects of OM applications had increasing trend from the beginning to the end of growing season. Organic matter application has positive influences on soil productivity; although these effects are not significant. We suggest that different OM sources which are usually available from crop residues in the region can be applied in arable soils poor in OM contents to enhance soil physical properties, aggregate formation, and aggregate stability. Further studies are needed to investigate the soil nutritional balance status affected by different OM sources in agro-ecosystems and to find out the best OM sources for each specific region. Acknowledgements This project was funded by the Soil and Water Research Institute of Iran. Also we thank the Fars agricultural Research Center for its cooperation. References Ahmad, R., Arshad, M., Khalid, A., Zahir, Z.A., 2008. Effectiveness of organic-biofertilizer supplemented with chemical fertilizers for improving soil water retention aggregate stability growth and nutrient uptake of maize (Zea mays L.). J. Sustain. Agric. 31 (4), 57–77. Albiach, R., Canet, R., Pomares, F., Ingelmo, F., 2001. Organic matter components, aggregate stability and biological activity in a horticultural soil fertilized with different rates of two sewage sludges during ten years. Bioresour. Technol. 77, 109–114. Amezketa, E., 1999. Soil aggregate stability: a review. J. Sustain. Agric. 14 (2, 3), 83–151. Assis, C.P., Oliveira, T.S., NLbrega Dantas, J.A., Mendonca, E., 2010. Organic matter and phosphorus fractions in irrigated agroecosystems in a semi-arid region of Northeastern Brazil. Agric. Ecosyst. Environ. 138, 74–82. Aulakh, M.S., Doran, J.W., Walters, D.T., Mosier, A.R., Francis, D.D., 1991. Crop residue type and placement effects on denitrification and mineralization. Soil Sci. Soc. Am. J. 55, 1020–1025. Aulakh, M.S., Khera, T.S., Doran, J.W., Bronson, K.F., 2001. Managing crop residue with green manure urea and tillage in a rice–wheat rotation. Soil Sci. Soc. Am. J. 65, 820–827. Barreto, R.C., Madari, B.E., Maddock, J.E.L., Machado, P.L.O.A., Torres, E., Franchini, J., Costa, A.R., 2009. The impact of soil management on aggregation, carbon stabilization and carbon loss as CO2 in the surface layer of a Rhodic Ferralsol in Southern Brazil. Agric. Ecosyst. Environ. 132, 243–251. Barthes, B., Azontonde, A., Boll, B., Prat, C., Roose, E., 2000. Field-scale run-off and erosion in relation to topsoil aggregate stability in three tropical regions (Benin Cameroon and Mexico). Eur. J. Soil Sci. 51, 485–495. Batjes, N.H., 1996. Total carbon and nitrogen in soils of the world. Eur. J. Soil Sci. 47, 151–163.
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Contents lists available at SciVerse ScienceDirect
Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee
Organic resource management: Impacts on soil aggregate stability and other soil physico-chemical properties Alidad Karami a , Mehdi Homaee a,∗ , Sadegh Afzalinia b , Hassan Ruhipour c , Sanaz Basirat d a
Department of Soil Science, Faculty of Agriculture, Tarbiat Modares University, Tehran, P.O. Box 14115-336, Iran Department of Agricultural Engineering Research, Fars Research Center for Agriculture and Natural Resources, P.O. Box 73415-111, Shiraz, Iran Hassan Ruhipour, Research Institute of Forests and Rangelands, Tehran, Iran d Faculty of Agriculture, Azad University of Shiraz, P.O. Box 7189815614, Shiraz, Iran b c
a r t i c l e
i n f o
Article history: Received 20 April 2011 Received in revised form 18 October 2011 Accepted 25 October 2011 Available online 15 December 2011 Keywords: Aggregate stability Bulk density Manure Organic matter
a b s t r a c t Effects of different types and amounts of organic matters (OM) on the soil aggregate stability indices as well as some soil properties were investigated. This study was conducted in the form of a split-plot experimental design with OM sources (sheep manure, cow manure, rice husk, finely chopped reeds, wheat straw, licorice (root) dregs) as main plot factors, and OM application rates (5, 15, and 25 ton ha−1 ) as sub-plot factors. Mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregate (WSA) were measured using both wet and dry sieving methods. The soil aggregate percents (SAP) > 0.84 mm and soil fragment percents (SFP) < 0.42 mm, water stable aggregate (WSA) > 0.5, WSA > 0.25 mm, soil bulk density (BD), and soil water infiltration were also measured in this study. Results showed that application of OM sources had positive effects on the soil MWD and GMD. The GMD and SAP > 0.84 mm increased following application of sheep and cow manure. The SAP > 0.84 mm, MWD, and GMD showed increasing trend from the beginning of the sowing stage to the end of the growing season. However, the SFP < 0.42 mm decreased for the same period. Applying all rates of OM increased the soil aggregate stability compared to the control treatment. The maximum values of MWD, GMD, WSA > 0.5, and WSA > 0.25 were obtained from 25 ton ha−1 OM application. In those plots that received cow manure, wheat straw, sheep manure, and rice husk, the WSA > 0.5 mm were higher than that of the control treatment. Application of OM increased OC, P, K, Mn, and Fe in the soil, while pH decreased with OM application. Applying different sources of OM decreased soil bulk density (BD) and increased infiltration rate. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Unfortunately, most soils in arid and semi-arid regions contain less than 1% organic matter. Soil organic matters restoration has beneficial effects on soil conservation, aggregate stability, soil physical properties improvement and attributes on the plant growth and crop production. Aggregate stability tests are necessary for a reliable description and ranking of soil behavior under water, wind, and field management effects (Amezketa, 1999). Soil organic matter loss is high in most soils of Iran due to high solar radiation, low soil moisture, and long-term intensive cropping. Soil organic matter may be lost rapidly under intensive cropping systems because of increased rate of organic carbon mineralization following tillage in addition to erosion losses and decreased OM returns through crop removal (Gregorich et al., 2001). Most soil scientists acknowledge
∗ Corresponding author. Tel.: +98 2148292280; fax: +98 2144196524; mobile: +98 9121483992. E-mail address: [email protected] (M. Homaee). 0167-8809/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2011.10.021
that soil organic matter conservation has positive effects on the soil properties (Chirinda et al., 2010; Hargreaves et al., 2008; Papini et al., 2011). These positive effects include higher water retention, higher cation exchange capacity, ability to retain nutrients within the root zone, greater buffering capacity against pH change, ability to chelate and form complex ions, contribution to soil structure, formation of stable aggregates, sustenance of soil biological activities, and biodiversity by providing food and habitat for soil animals and microorganisms (Degens et al., 2000). In agricultural systems, conserving soil organic carbon has been recognized as a strategy to reduce soil degradation. On the other hand, residue management, artificial addition of OM sources, to the soil and clay mineral, and sesquioxide of soil are the most important factors in the soil structural development and soil aggregation improvement (Bhattacharyya et al., 2009; Wagner et al., 2007). Although, it is practically impossible to alter the clay mineral and sesquioxide content of soil for the large areas, increasing the SOM content in the field is feasible (Aulakh et al., 2001). Topsoil is a huge terrestrial reservoir of carbon which has a modifying effect on the carbon dioxide concentrations in the
A. Karami et al. / Agriculture, Ecosystems and Environment 148 (2012) 22–28
atmosphere and can thus influence climate warming and environmental processes at a global scale (Barreto et al., 2009). Soil organic matter is a big source of nitrogen (N) and over 90% of N in soils is in organic form (Batjes, 1996). Application of sludge could increase the soil organic carbon and provide hydrolyzable carbohydrate content and greater structural stability (Ojeda et al., 2008). Well-established strategies for increasing SOM contents in agricultural production systems include the production and incorporation of green manure crops (Aulakh et al., 2001; Bejbaruha et al., 2009; Gerzabek et al., 2001), application of livestock manure (Gerzabek et al., 2001), and crop residue incorporation into the topsoil, with a subsequent increase in mineralization and microbial biomass (Hargreaves et al., 2008). The incorporation of barley straw was reported to be most effective for water-stable aggregates development in the soils with 34% and 38% clay (Wagner et al., 2007). Applying 3.1 and 12.4 ton ha−1 straw to the soil could also increase soil aggregation by about 100% and 250%, respectively (Wagner et al., 2007). Tillage has different effects on the soil ecosystem including soil carbon and nitrogen reduction, soil structure degradation, microbial community alteration, and consequently microbial biomass reduction (DuPont et al., 2010). Tejada et al. (2006) found that organic matter acted as a cementing factor necessary for flocculating soil particles and forming stable aggregates. Tejada et al. (2007) showed that composted OM sources had a positive effect on the soil properties such as structural stability, microbial biomass, soil respiration, urease, dehydrogenase, BBA-protease, aˆ-glucosidase, soil phosphatase activities, and bulk density. They also reported that organic by-products resulting from industrial processes represented an important source of nutrients especially for organic fertilization. The improvement of soil structure through addition of OM will lead to a high degree of aggregation and a large portion of soil aggregates in the size range of 1–10 mm, which remain stable when wetted (Tisdall and Oades, 1982). Soils with good structure, generally provides suitable soil physical properties including a high water-holding capacity, moderate saturated hydraulic conductivity, and sufficient aeration for plant establishment and growth (Riahi et al., 2009; Tisdall and Oades, 1982). Depending on the extent of disruption caused by agricultural practices such as tillage and incorporation of organic matter into soil, aggregates can provide physical protection of SOM and retard its decomposition (Kravchenko and Thelen, 2009; Pulleman and Marinissen, 2004). Furthermore, a favorable soil structure greatly increases soil resistance to both wind and water erosion (Barthes et al., 2000; Bilalis and Karamanos, 2010). Hydrogen bonding between polar groups of the organic molecules and adsorbed water molecules or oxygen of the silicate surface may contribute to greater aggregate stability. Consequently, the amount of mechanical stress that a soil can withstand will generally be increased by the presence of OM (Zhang et al., 2005). Maintaining soil quality at the surface is necessary to have a safe soil and adequate production. In this sense, the protection and increasing soil OM is essential to keep adequate levels of organic C (Lpez-Garrido et al., 2011; Ryan et al., 2006). Reduced aggregate stability may decrease rate of water infiltration and crop production and increase slaking and crusting, and runoff erosion. Applying OM can also improve water storage, sources of biodiversity, retention of contaminants, faster decomposition of wastes, and erosion control (Ahmad et al., 2008). Saha and Mishra (2009) concluded that annual organic manure application or organic residue conservation may mitigate the negative effect of puddling and related properties; therefore, could contribute to the sustainability of the wetland rice ecosystem. In our region, high solar radiation, arid climate condition, excessive use of chemical fertilizers, residue removal, and improper field
23
management decrease soil OC and soil quality attributes. Losses of soil OM are reflected in adverse modifications in soil biological, chemical and physical properties, such as reduced soil biodiversity, soil buffering capacity, cation exchange capacity, nutrient availability, water infiltration, and increased destruction of soil structure, soil compaction and erosion. Because of beneficial role of OM on soil quality, as an effective soil component in stabilizing soil structure and controlling soil resistance to erosion, and its stabilizing role on the aggregation and aggregate stability, this study was conducted to assess the effect of different sources and amounts of OM on the soil aggregate stability and some related soil physico-chemical properties at field scale. Therefore, an understanding of the effects of applying different OM sources and rates on aggregation and aggregate stability, and other soil physico-chemical properties on a large scale in arid and semi-arid regions is novel in this research. 2. Materials and methods 2.1. Experimental design The study was conducted in Zarghan area located at southern Iran with an average annual rainfall of 330 mm, minimum longterm temperature of 7.4 ◦ C, and maximum temperature of 24.7 ◦ C. A field experiment was conducted in a split-plot design with OM sources (sheep manure (SM), cow manure (CM), rice husk (RH), finely chopped reeds (FCR) or phragmites-australis (cav.), wheat straw (WS), licorice (root) dregs (LD), and a treatment without applying any sources of OM or control treatment (CT)) as main plots and OM application rates (5, 15, and 25 ton ha−1 ) as sub-plots with three replications in three consecutive years. The applied organic amendments were loosely mixed with the topsoil. The measured indices consisted of soil aggregate mean weight diameter (MWD), geometric mean weight diameter of soil aggregates (GMD), SAP > 0.84 and SFP < 0.42 mm, soil bulk density (BD), water infiltration rate, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm. Some soil properties such as soil moisture content (SMC), pH, EC, OC, Pavailable , Kavailable , Mn, Fe, Ca + Mg, Na, and sodium absorption ratio (SAR) under different OM applications were also measured. 2.2. Soil sampling and analyses To determine the soil aggregate MWD, samples were taken at three stages; before applying the OM and before planting, mid plant growing period (11 weeks after planting), and after plant harvesting. A metal box of 170 mm × 170 mm × 50 mm was used to take the samples. The samples were delivered to a laboratory to separate plant roots and residues. The aggregate stability was measured using both wet and dry sieving methods. In dry sieving method, soil samples were divided into seven different classes using a standard set of dry sieves. These classes were consisted of soil aggregates and fragments < 0.42 mm, 0.42–0.84 mm, 0.84–2 mm, 2–4 mm, 4–6.4 mm, 6.4–12.7 mm, and 12.7–38 mm. SAP > 0.84 and SFP < 0.42 mm, MWD, and GMD were calculated to determine soil erodibility against wind using dry sieving method. The MWD and GMD were calculated using the following equation (Oguike and Mbagwu, 2009): MWD =
n
X¯ i Wi
(1)
i=1
where X¯ i is the mean diameter of aggregates over each sieve size, Wi is weight of the aggregates in that size range as a fraction of total dry weight of the sample analyzed, and n is number of sieves. This parameter gives the aggregate size distribution.
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Table 1 Some chemical properties of different OM sources used in the study. OM sources
EC (dS m−1 )
pH
T.N.V. (%)
OC (%)
P (mg kg−1 )
K (mg kg−1 )
Fe (mg kg−1 )
Zn (mg kg−1 )
Cu (mg kg−1 )
Mn (mg kg−1 )
LD RH FCR WS SM CM
0.56 1.07 1.77 1.77 4.08 4.23
7.7 6.6 4.8 5.6 7.2 8.7
4.50 1.25 0.50 8.25 6.00 13.25
54.10 44.34 52.97 38.74 45.08 40.57
0.07 0.05 0.07 0.12 0.72 0.7
0.24 0.52 0.53 1.49 2.71 3.22
3737 519 466 529 2500 3866
44.35 31.95 12.40 27.30 62.35 70.60
20.1 2.6 3.6 10.3 19.6 21.2
62.35 103.25 229.05 193.30 145.85 211.85
LD: licorice (root) dregs, RH: rice husk, FCR: finely chopped reeds, WS: wheat straw, SM: sheep manure, CM: cow manure.
The geometric mean diameter of aggregates was calculated based on:
n W log X¯ i i=1 i GMD = exp n n
i=1
Wi
(2)
W is the total weight of aggregates. where i=1 i The water stable aggregate index which accounts for aggregate stability was calculated using the following equation: WSA =
Mr × 100 Mt
(3)
where Mr is mass of resistant aggregates and Mt is the total mass of wet sieved soil. To determine aggregate stability and related size distribution at wet condition, a wet sieving (2–4 mm mesh sieve) method was used with 50 g soil samples. Consequently, six sieves having 0.075, 0.106, 0.25, 0.5, 1, and 2 mm mesh diameter were used. Measurement of aggregate size distribution was accomplished by shaking the sieves for 10 min. The weight of soil on each sieve, total soil weight, and ratio of aggregate weights on each sieve to the total soil weights were then calculated. The soil bulk density was determined using core sampling method at the soil depth ranges of 0–15, 15–30, and 30–45 cm. The infiltration rate in the experimental plots was measured using the double rings method. Different physical and empirical models were tested and the Kostiakov model (Kostiakov, 1932) with following form was best fitted to the obtained experimental data: I = at b
(4)
i = bat (b−1)
(5)
where I (L) is cumulative infiltration, t (T) is time, i (L T−1 ) is infiltration rate, and a and b are empirical constants. The nutrient element contents of different OM sources including P, K, Zn, Cu, and Mn were measured. Soil organic carbon and available forms of P, K, Na, Mn, and Fe under influence of different OM sources were also measured in this research using standard plant and soil analysis methods (Waling et al., 1989).
contained the highest amount of Mn concentration and LD had the highest amount of OC. The applied cow manure had the maximum K, Fe, Zn, Cu, T.N.V., EC, and pH. The maximum P concentration was related to the sheep manure. Results also indicated that OM sources had significant influence on the MWD and GMD so that the largest MWD value was obtained from RH application and the lowest MWD value was related to CM application. However, there was no significant difference between MWD value obtained from RH, WS, FCR, LD, CT, and SM applications (Fig. 1). The data presented in Table 2 indicated that application of OM sources had a significant effect on WSA > 0.5, WSA > 0.25, WSA > 0.106, SFP < 0.42, and SAP > 0.84 mm indices. So that, the highest WSA > 0.5 mm was obtained from the application of wheat straw, licorice (root) dregs, and rice husk. The minimum value of this index belonged to the cow manure. The maximum and minimum values of WSA > 0.25 and WSA > 0.106 mm were obtained from the applied cow manure and finely chopped reeds application, respectively. Meanwhile, the trend of mean soil fragments < 0.42 mm approximately contradicted SAP > 0.84 mm. The maximum value of SAP > 0.84 mm and the minimum amount of SFP < 0.42 mm were related to the sheep manure. The maximum MWD and GMD obtained values from the dry sieving method belonged to the sheep manure (Fig. 2). The obtained mean values of MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm under different organic matter amounts are presented in Table 3. The data presented in this table indicated that the soil MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm increased by increasing the applied OM quantity, so that the maximum MWD, GMD, WSA > 0.5, WSA > 0.25, and WSA > 0.106 mm values were obtained from the maximum amount of OM application (25 ton ha−1 ). Although these results indicate that the OM rate had a significant influence on the stable aggregates, there was no significant difference between the stable aggregates on the sieve with 0.106 mm mesh under different amounts of OM application. By increasing the amount of applied OM, the soil BD was signif-
2.3. Statistical analyses The collected data were then analyzed using SAS software (SAS Institute, Cary, NC). The independent variables consisted of OM sources and rates, and the dependent variables were considered to be MWD, GMD, SAP > 0.84 mm, SFP < 0.42 mm, (BD), water infiltration rate, WSA > 0.5, WSA > 0.25, WSA > 0.106 mm, soil moisture content (SMC), organic carbon, P, K, Mn, Fe, Ca + Mg, SAR, and Na. The obtained mean values were compared using the Duncan’s multiple range tests at 5% and 1% levels of significance. 3. Results Results of nutrient contents of different OM sources are presented in Table 1. These results show that the finely chopped reeds
Fig. 1. Comparison of different OM sources for the mean MWD and GMD values obtained from wet sieve set method. LD: licorice (root) dregs, RH: rice husk, FCR: finely chopped reeds, WS: wheat straw, SM: sheep manure, CM: cow manure, CT: control treatment.
A. Karami et al. / Agriculture, Ecosystems and Environment 148 (2012) 22–28
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Table 2 Mean values of WSA > 0.5, WSA > 0.25, WSA > 0.106, SFP < 0.42, and SAP > 0.84 mm under application of different OM sources. OM sources
WSA > 0.5 (%)
WSA > 0.25 (%)
WSA > 0.106 (%)
SFP < 0.42 (%)
SAP > 0.84 (%)
WS LD RH FCR CT SM CM
36.86A* 36.75A* 36.40A* 34.76AB* 33.72AB* 33.66AB* 29.68B*
83.86AB* 83.01AB* 85.60AB* 78.14B* 82.81AB* 84.64AB* 87.94A*
96.07A* 94.38AB* 95.94A* 93.41B* 94.88AB* 95.95A* 96.46A*
14.83A** 16.08A** 15.26A** 15.57A** 15.02A** 12.05B** 13.54AB**
72.53BC** 70.88C** 72.45BC** 72.40BC** 72.99BC** 77.55A** 75.13AB**
WSA: water stable aggregate, SFP: soil fragment percent, SAP: soil aggregate percent, CT: control treatment. * Significant at 5%. ** Significant at 1%. Table 3 The obtained mean values of MWD, GMD, BD, SMC, OC, P, K, Mn and water stable aggregates over 0.5, 0.25, and 0.106 mm under different amount of organic matter applications. OM (ton ha−1 )
MWD (mm)
GMD (mm)
WSA > 0.5 (%)
WSA > 0.25 (%)
WSA > 0.106 (%)
BD (g cm−3 )
SMC (%)
OC (%)
Pavailable (mg kg−1 )
Kavailable (mg kg−1 )
Mn (mg kg−1 )
25 15 5
0.93A** 0.81B** 0.83B**
0.79A** 0.75B** 0.74B**
37.29A* 33.04B* 33.31B*
87.15A* 83.63B* 80.37B*
87.15A* 95.25A* 94.76A*
1.20B* 1.23AB* 1.24A*
30A** 27B** 26B**
1.13A** 1.04A** 0.90B**
18.33A* 14.26B* 14.7AB*
470.6A** 436.0B** 432.4B**
21.21A** 20.63A** 18.42B**
BD: bulk density, SMC: soil moisture content OC: organic carbon.
Fig. 2. The influence of different organic matter sources on the mean MWD and GMD obtained from dry sieving method.
icantly reduced and soil moisture retention increased. The soil OC, P, K, and Mn concentrations also increased by increasing OM rates. So that, their maximum amounts were obtained from the treatment with 25 ton ha−1 OM application. The results presented in Table 4 indicated that MWD and GMD increased from the beginning to the end of the growth season. The variation of bulk density, soil moisture content (SMC), organic carbon (OC), P(available) , K(available) , Mn, and Fe concentration under different OM sources applied are presented in Table 5. In spite of lack of difference between the bulk densities under different OM sources, applying finely chopped reeds and the control treatment (without OM) provided the minimum and the maximum bulk density values, respectively. The data presented in Table 5 showed that all the applied OM sources increased the soil OC in such a way that applying licorice (root) dregs had the highest and the control treatment had the lowest amount of OC. The maximum soil phosphorus content was obtained from the applied cow manure, while applying sheep manure had the second place. All the OM sources used increased soil potassium so that applying cow manure had the most significant influence. The soil Mn concentration increased with applying different OM sources; therefore, the control treatment had the minimum amount of soil Mn. Since the licorice (root) dregs treatment
Table 4 Comparison of means MWD and GMD, SFP < 0.42 and SAP > 0.84 mm obtained from dry sieving method at different stages of cultivation. Sampling time
MWD (mm)
GMD (mm)
SFP < 0.42 (%)
SAP > 0.84 (%)
Beginning of cultivation season Middle of cultivation season End of cultivation season
6.51C* 7.65B* 8.77A*
1.49C* 1.61B* 1.76A*
16.76A** 14.62B** 12.48C**
69.89C** 73.42B** 76.95A**
Table 5 Comparison of mean soil bulk density, moisture content, OC, Ca + Mg, SAR, Na+, P, K, Mn, and Fe under application of different OM sources. OM sources
BD (g cm−3 )
SMC (%)
OC (%)
Ca + Mg (%)
SAR
Na+ (mg kg−1 )
Pavailable (mg kg−1 )
Kavailable (mg kg−1 )
Mn (mg kg−1 )
Fe (mg kg−1 )
LD RH CM FCR WS SM CT
1.25A* 1.23A* 1.20A* 1.19A* 1.21A* 1.21A* 1.27A*
31AB* 33A* 26BCD* 25CD* 30ABC* 26BCD* 24D*
1.5A** 1.1B** 1.1B** 1.0B** 0.95B** 0.95B** 0.74C**
8.4Ans 8.5Ans 6.9Ans 8.6Ans 9.2Ans 7.1Ans 6.9Ans
2.35Ans 2.05Ans 2.05Ans 2.26Ans 1.88Ans 2.00Ans 2.34Ans
4.62Ans 4.15Ans 3.78Ans 4.72Ans 4.04Ans 3.78Ans 4.23Ans
10.73C** 9.32C** 34.83A** 9.91C** 10.10C** 23.26B** 12.10C**
402.4C** 443.6BC** 530.9A** 433.6BC** 447.1BC** 478.0AB** 388.9C**
21.19A** 22.19A** 20.47AB** 20.50AB** 20.98A** 18.92AB** 16.33B**
14.35A** 8.29D** 12.74B** 9.94C** 11.79B** 12.25B** 12.35B**
SAR: sodium adsorption ratio.
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contained a large amount of Fe, this treatment provided a soil with the maximum amount of Fe. Although different OM sources had no significant influence on Ca + Mg, sodium adsorption ratio (SAR), and Na concentration, they increased soil Ca and Mg and decreased the SAR leading to a positive effect on the particle coagulation and aggregation. These results are very important for application of OM sources such as cow manure that are saline. Applying different OM sources had positive effect on the soil infiltration rate and a and b parameters of Kostiakov model. Applying different OM sources also significantly increased the infiltration rate. This can be attributed to the positive effects of organic matter on the aggregation and enhancement of soil physical properties (data not shown).
4. Discussion Results of this study demonstrated that application of OM sources had positive effects on the soil physico-chemical properties. On the other hand, there are Great Plains at south Iran with intensive cultivation systems and poor soil management strategies. Therefore, residual management is very important for preserving natural ecosystems (De Bona et al., 2008). Another problem for this area is conventional tillage that reduces the fungal biomass and destroys the aggregates and organic matter (Mele and Crowley, 2008) which prompts deterioration of soil hydrological properties. The obtained results indicated that components of applied OM sources were very different (Table 1). These variations were related to nature and characteristics of OM types. Accordingly, the highest EC, pH, T.N.V., K, Fe, Zn, Cu, and Mn values were belonged to cow manure, while the lowest values belonged to LD, FCR, FCR, RH, FCR, FCR, RH, and LD, respectively. These results indicated that although cow manure is rich of nutrient elements, its application has limitation particularly in arid and semi-arid regions due to salinity. On the other hand, the lowest pH value in FCR is very valuable for calcareous soils that are dominant soil formations in arid and semiarid regions. Practically, the lowest value of EC and highest value of OC in LD are very important factors for OM applications in arid and semi-arid regions. The obtained results also indicated that the MWD, GMD, and SAP > 0.84 mm increased following application of sheep and cow manure. Results of similar field trial showed that long-term manure application promoted the formation of soil macro aggregates and increased aggregate stability (Li et al., 2010). Therefore, one may conclude that the applied sheep and cow manure has generally positive effects on the soil aggregation. The MWD, GMD, and the SAP > 0.84 mm had an increasing trend from the beginning of the sowing stage up to end of the growth season. The soil fragment percents < 0.42 mm decreased as time passed by. This observation describes the fact that increasing decomposition of OM and development of plant roots enhanced both aggregation and aggregate stability. At the end of cultivation season, the SAP > 0.84 mm significantly increased, while SFP < 0.42 mm was reduced. These results indicated that during the plant growth period, both decomposition of applied OM and root development acted as two positive factors influencing aggregation. Tillage operation stimulates the oxidation of SOC, increases residue incorporation into soil, fragments macro-aggregates, and increases surface area for soil microbial activity and decomposing the organic matter which improves soil physical condition (Aulakh et al., 1991; Coppens et al., 2007; Fontaine et al., 2007). This improved soil physical condition could accelerate the decomposing process of the incorporated OM sources and lead to the soil aggregation. The MWD maximum value was obtained from the highest amount of applied organic matter. The soil aggregate stability
increased by application of rice husk, wheat straw, finely chopped reeds, and licorice (root) dregs compared to the control treatment. The highest values of MWD, GMD, WSA > 0.5, WSA > 0.25 mm, SMC, P, K, and Mn were obtained from applying 25 ton ha−1 organic matter. These results indicated that application of OM improved soil physico-chemical properties. It was interesting that the most water stable aggregates remained on the sieves with larger mesh. The WSA > 0.5 mm of the treatments with application of cow manure, wheat straw, sheep manure, and rice husk was larger than that of the control treatment. In this context, Huang et al. (2010) concluded that the positive trends in corn yield and soil productivity treatments with manure application are attributed mainly to the improvement in soil quality. Improved soil aggregation and structure could benefit the crop growth through stimulating root distribution and uptake of water and nutrients (Pachepsky and Rawls, 2003; Bronick and Lal, 2005). In the arid and semi-arid climate, with conventional soil management, deep ploughing brings the material poor in organic matter to the topsoil and applying inorganic fertilizers accelerates humus and organic residues decomposition and consequently reduces aggregate stability (Chirinda et al., 2010). The increase in aggregate stability likely enhances the soil resistance to erosion which is a major threat for crop production and agricultural sustainability (Zhang and Xu, 2005). Therefore, application of organic matter can improve crop yield, soil fertility, and soil physical properties (Naylor et al., 2005; Ju et al., 2006; Li et al., 2010). Intensive cultivation of agro-ecosystems with removed or burned residue has led to loss of soil organic carbon. Therefore, adoption of proper management practices has been suggested to be an effective way to increase the soil quality (Smith, 2004). Application of OM increased the OC, P, K, Mn, and Fe concentrations in the soil and decreased soil pH. Under organic management, deliberate attempts are made to increase soil organic carbon (SOC) levels and enhance nutrient cycling through application of manure and other OM sources (Olesen et al., 2007). Our results indicated that application of OM enhanced the soil fertility status. Using different OM sources increased the soil water infiltration and decreased the soil bulk density. The obtained cumulative infiltration data from application of each OM sources had significant difference with that of CT, such that the largest and lowest cumulative infiltration values were obtained from WS application and CT, respectively (data not shown). These findings are in concurrence with what has been reported by previous investigators. For instance Albiach et al. (2001) reported that application of the organic matter has a positive effect on aggregation, infiltration increases and soil erosion decreases (Ojeda et al., 2003). Khormali et al. (2009) found out that following of deforestation, as a result of considerable losses of organic carbon and breakdown of aggregates, MWD and soil infiltration rate decreased and BD increased. Aggregation is a soil quality indicator that is positively related to the physical protection of organic matter, improved water infiltration, and reduced soil erosion (Rhoton et al., 2002). Mele and Crowley (2008) pointed out that soil aggregate formation leads to better infiltration and organic matter accumulation. On the other hand, application of OM improved aggregation and aggregate stability. These results are in good agreement with those obtained by Bayu et al. (2005) and Verkler et al. (2009). Furthermore, Papini et al. (2011) reported that the organic matter itself enhanced soil resistance to compaction through several mechanisms (strengthening of binding forces among particles and aggregates and increasing elasticity of aggregates under compression) and provided a higher porosity and lower soil bulk density. Different OM sources also significantly increased soil water content and soil moisture capacity. Luo et al. (2010) reported that double cropping per year, can lead to more production of residues and roots than single cropping;
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therefore, double cropping system increases soil carbon stock, reduces soil erosion, and improves soil structure and nutrient cycling. Contrary to this report, in our studied region the annual double cropping can lead to residue removing or burning. Consequently, double cropping in our condition decreases soil carbon, increases soil erosion, and adversely affects the soil structure as well as nutrient cycling. Our observation implied that high solar radiation, residue removal, and unfavorable field management were main factors influencing on the soil quality attributes. Other researchers (Assis et al., 2010; Lemke et al., 2010) have shown that these factors influence soil quality (e.g., N and C mineralization, light fraction organic matter, microbial biomass carbon and soil aggregate stability). 5. Conclusions Application of different OM sources had significant influences on soil MWD, GMD, and SAP > 0.84, such that these indices increased with sheep and cow manure applications. Soil MWD, GMD, WSA > 0.5, and WSA > 0.25 increased by increasing OM application rates, such that the maximum values of these parameters were attained with maximum rate of OM application (25 ton ha−1 ). Soil water retention increased by increasing OM application rates, while soil bulk density decreases by increasing OM application rate. Positive effects of OM applications had increasing trend from the beginning to the end of growing season. Organic matter application has positive influences on soil productivity; although these effects are not significant. We suggest that different OM sources which are usually available from crop residues in the region can be applied in arable soils poor in OM contents to enhance soil physical properties, aggregate formation, and aggregate stability. Further studies are needed to investigate the soil nutritional balance status affected by different OM sources in agro-ecosystems and to find out the best OM sources for each specific region. Acknowledgements This project was funded by the Soil and Water Research Institute of Iran. Also we thank the Fars agricultural Research Center for its cooperation. References Ahmad, R., Arshad, M., Khalid, A., Zahir, Z.A., 2008. Effectiveness of organic-biofertilizer supplemented with chemical fertilizers for improving soil water retention aggregate stability growth and nutrient uptake of maize (Zea mays L.). J. Sustain. Agric. 31 (4), 57–77. Albiach, R., Canet, R., Pomares, F., Ingelmo, F., 2001. Organic matter components, aggregate stability and biological activity in a horticultural soil fertilized with different rates of two sewage sludges during ten years. Bioresour. Technol. 77, 109–114. Amezketa, E., 1999. Soil aggregate stability: a review. J. Sustain. Agric. 14 (2, 3), 83–151. Assis, C.P., Oliveira, T.S., NLbrega Dantas, J.A., Mendonca, E., 2010. Organic matter and phosphorus fractions in irrigated agroecosystems in a semi-arid region of Northeastern Brazil. Agric. Ecosyst. Environ. 138, 74–82. Aulakh, M.S., Doran, J.W., Walters, D.T., Mosier, A.R., Francis, D.D., 1991. Crop residue type and placement effects on denitrification and mineralization. Soil Sci. Soc. Am. J. 55, 1020–1025. Aulakh, M.S., Khera, T.S., Doran, J.W., Bronson, K.F., 2001. Managing crop residue with green manure urea and tillage in a rice–wheat rotation. Soil Sci. Soc. Am. J. 65, 820–827. Barreto, R.C., Madari, B.E., Maddock, J.E.L., Machado, P.L.O.A., Torres, E., Franchini, J., Costa, A.R., 2009. The impact of soil management on aggregation, carbon stabilization and carbon loss as CO2 in the surface layer of a Rhodic Ferralsol in Southern Brazil. Agric. Ecosyst. Environ. 132, 243–251. Barthes, B., Azontonde, A., Boll, B., Prat, C., Roose, E., 2000. Field-scale run-off and erosion in relation to topsoil aggregate stability in three tropical regions (Benin Cameroon and Mexico). Eur. J. Soil Sci. 51, 485–495. Batjes, N.H., 1996. Total carbon and nitrogen in soils of the world. Eur. J. Soil Sci. 47, 151–163.
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