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Effect of burned rice straw, phosphorus and nitrogen fertilization on wheat (Triticum aestivum L.)
Annals of Agricultural Science 62 (2017) 113–120
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Effect of burned rice straw, phosphorus and nitrogen fertilization on wheat (Triticum aestivum L.) El-Sayed E.A. El-Sobky Agronomy Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt
a r t i c l e
i n f o
Article history: Received 23 February 2017 Received in revised form 18 May 2017 Accepted 21 May 2017 Available online 7 June 2017 Keywords: Wheat Rice straw Phosphorus Nitrogen Yield attributes
a b s t r a c t This investigation was carried out in the Experimental Farm at Ghazala Village (Faculty of Agriculture, Zagazig University, Egypt) during two successive seasons (2014/2015 and 2015/2016) to study the effect of rice straw burning (rice straw plowing down and rice straw burning), phosphorus (P) level (0 and 15.5 kg P2O5/fad [fad = faddan = 4200 m2 and ha = 2.38 fad]), and nitrogen (N) level (30, 60 and 90 kg N/fad) on wheat (Triticum aestivum L. cv. Gemmiza 11). Burned rice straw significantly decreased the flag leaf area, spikes number/m2, 1000-grain weight, grain and total yields/fad. The increase of P level to 15.5 kg P2O5/fad produced significant increase in plant height, flag leaf area, grain weight per spike, 1000-grain weight but, decreased the number of spikes/m2 and the grain yield/fad and harvest index. The increase of N level up to 90 kg N/fad gave significant increase in grain yield and yield attributes except the number of sterile spikeletes/spike and 1000-grain weight which were decreased. Ó 2017 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-ncnd/4.0/).
Introduction Rice (Oryzae sativa L.) is an important cereal crop which ranks the second after wheat in Egypt where cultivated area reached 1.37 million fad (FAOSTAT, 2017). Rice farmer have got used to burn rice straw as they believe in some gained benefits to their soil fertility or as a measure of controlling pest damage. They found burning is the cheapest and easiest way for removing large loads of the produced rice straw. Also, burning of straw is mainly caused by the need of a short turnover time between rice and following crops. The next crop (wheat or other crops) will have the highest yields when this crop can be established as early in the autumn period as possible, thereby benefiting from higher temperatures and longer days as well as, it much easier to prepare a seedbed for the following crop. There are various options for incorporating the straw into the field as alternative for burning but these options generally require mechanization, water, and additional fertilizer in order for rice straw to quickly decompose in the field. In addition, the degradation of straw may also lead to significant emissions of gases, such as methane (Bakker et al., 2013). Due to the large rice cultivated area during the last decades, burning rice straw has become one of the main sources to air pollution, where the large losses going into the atmosphere up to 80% of N (Dobermann
and Witt, 2000 and Dobermann and Fairhurst, 2002), 25% of P and 21% of potassium (K) (Ponnamperuma, 1984), 4–60% of sulphur (S) (Lefroy et al., 1994) are reported. Addition of P and N fertilizers under these conditions could possibly increase gained benefits through enriching soil fertility. Several authors reported significant increase of grain yield and yield attributes due to the addition of P fertilizer up to 45, 22, 15.5 and 11 kg P2O5/fad as reported by El-Gizawy (2009), Youssef et al. (2013), Salim and Abou El-Yazied (2015) and Ram et al. (2015). Also, Lehoczkyb et al. (2012) and Sandaña and Pinochet (2014) showed that, the increase P levels up to 42 and 105 kg P2O5/fad increased wheat grain yield, biomass and its components. Nitrogen is an essential nutrient for plant growth and development being involved in vital plant functions such as photosynthesis, DNA synthesis, protein formation and respiration (Rana et al., 2012 and Diacono et al., 2013). Many studies revealed that, the increase of N levels significantly increased yield and yield attributes of wheat i.e. number of spikes/m2, flag leaf area, plant height, spike length, number of spikeletes and grains/spike, 1000-grain weight due to the addition of N fertilizer up to 90, 75.5, 100, 75, 80, 42, 63 and 50 kg N/fad as reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014), Violeta et al. (2015) and Bhatt et al. (2016).
Peer review under responsibility of Faculty of Agriculture, Ain-Shams University. E-mail address: [email protected] http://dx.doi.org/10.1016/j.aoas.2017.05.007 0570-1783/Ó 2017 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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Therefore, the present study aimed to investigate the effect of burning of rice straw on the growth and yield of wheat under different levels of P and N fertilization. Materials and methods The present study was conceded at Ghazala Village, Fac. of Agric., Zagazig Univ., Sharkia Governorate, Egypt (30.11°N, 31.41°E) during two successive seasons (2014/2015 and 2015/2016) of wheat plant in a clay soil. For soil properties, soil samples were collected from the experimental sites at the depth of 0–30 cm before planting to determine soil physical and chemical properties according to Black (1982). Soil analysis showed that soil had clay in texture having 20.61% sand, 31.82% silt, 47.57% clay, 1.03% organic matter and C: N ratio of 12:1. It had of total N 0.05%, available P of 8.15 ppm, available K of 149.3 ppm, available Fe of 1.75 ppm, available Zn of 0.51 ppm, available Mn of 0.31 ppm and 8.02 pH (Moderately alkaline) as averages of both seasons. The atomic absorption spectrophotometer was used to determine Zn, Fe and Mn. Moreover, rice straw was determined according to A. O.A.C. (2000) where rice straw analysis showed that it had having 0.39% Total N, 310 ppm available P, 38% organic matter and C: N ratio of 57: 1, as averages of both seasons. Wheat (Triticum aestivum L. cv. Gemmiza 11) was sown in the last week of November in the two seasons. Sowing was made in rows 15 cm apart. Each 2nd order sub plot included 20 rows of 3 m length (9 m2). Sowing was made after rice as a preceding crop in both seasons using seeding rates of 70 kg/fad. Flood irrigation was practiced in one month interval and was withheld one month before harvest which was made during the last week of April. Studied Factors A: Rice straw treatments: 1. Rice stubble: The stubble of rice i.e. residues was plowed down as recommended before sowing wheat. 2. Burned rice straw before sowing wheat. An average straw yield of 6 ton/fad of the preceding rice crop was burned and plowed down at the depth of 30 cm before seedbed preparation for wheat. B: Phosphorus fertilization levels: 1. 0 kg P2O5/fad: Without P fertilization. 2. 15.5 kg P2O5/fad: P at a level of 15.5 kg P2O5/fad as ordinary superphosphate (15.5% P2O5) was band placed at the time of sowing. C: Nitrogen fertilization levels: 1. 30 kg N/fad. 2. 60 kg N/fad. 3. 90 kg N/fad. One fifth of N fertilization levels was added as basal dose before sowing wheat as ammonium sulphate (20.5%). The rest of these two N levels was split and partly added before the first and second irrigations as ammonium nitrate (33.5% N). Plots were surrounded by wide borders (0.75 m) to prevent movement of nutrients from fertilized to non-fertilized plots. Experimental design: A split-split plot design of four replications was used, where the rice straw treatments were allocated in the main plots. P and N fertilization levels were allocated in the first and second (9 m2) order subplots, respectively. Vegetative parameters: At heading, ten guarded plants were taken at random from each experimental plot to determine plant
height (cm) and flag leaf area (cm2) which was determined according Lal and Subba Rao (1951) by using blade length maximum blade width 0.72. Reproductive parameters: Number of spikes/m2 (recorded from 1 m2 using a wooden square). A bordered area of 1.0 m length (0.15 m2), previously labeled in the other 3rd row after emergence (10 days after sowing), was harvested where the following yield and yield attributes were recorded on 10 plants: plant height (cm), spike length (cm), number of fertile and sterile spikeletes/ spike, number of grains/spike, grain weight/spike (g), 1000-grain weight (g). The grain, straw and total yields (ton/fad) were calculated using the yields obtained from 1.0 m2 and harvest index (%) i.e., grain to total yield in percentage. Statistical analysis Data were statistically analyzed according to Gomez and Gomez (1984) by using MSTAT-C (1991) where statistical program Version 2.1 was used for analysis of variance (ANOVA). Duncan Multiple range test was used to compare statistical significant differences (Duncan, 1955). In interaction tables, capital and small letters were used to denote significant differences among rows and columns ˆ max) means, respectively. The predicated maximum trait average (Y which could have been obtained due to the addition of the predicted maximum N level (Xmax) are also included. The response equations were calculated according to Snedecor and Cochran (1967) using the orthogonal polynomial tables. The significancy of the linear and quadratic components of each of these equations was tested, then the response could be described as linear (first order) or quadratic (second order). The predicted maximum averˆ max) which could have been obtained due to the addition ages (Y of the predicted maximum N level (Xmax) were calculated according to Neter et al. (1990) as explained by Abdul Galil et al. (2003) using the following equations:
^ max ¼ Y ^ 0 þ b2 =4c Y
Xmax ¼ X0 þ b=2cðuÞ
where Yˆ0 = Grain yield at the lowest N level i.e. zero kg N/fad (ton/fad). b = Measures the linear component of the response equation. c = Measures the quadratic component of the response equation. u = unit of N = 30 kg N/fad. Results and discussion Plant height, flag leaf area and spike length. Rice straw treatments effect Plant height and spike length were not significantly affected by rice straw treatments in both seasons and their combined. However, flag leaf area of wheat grown after rice straw burning was decreased (Table 1). These results clearly indicate that burning of rice straw causes almost complete N loss, P losses of about 25%, K losses of 21%, and S losses of 4–60% (Ponnamperuma, 1984; Lefroy et al., 1994 and Dobermann and Fairhurst, 2002) and hence caused shortage of soil available nutrients and therefore reflected the decrease in wheat flag leaf area. P Level effect In both seasons and their combined, the increase of P level to 15.5 kg P2O5/fad produced significant increase in plant height, which was also observed in flag leaf area in the second season and the combined analysis (Table 1). However, spike length was decreased due to addition P (15.5 kg P2O5/fad) compared with without P application (0 kg P2O5/fad). These results are in harmony
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Table 1 Plant height, flag leaf area and spike length of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
Flag leaf area (cm2)
Plant height (cm)
Spike length (cm)
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
Rice straw treatments (S) Rice stubble Burned straw F.test
104.5 110.3 N.S.
111.4 110.5 N.S.
107.9 110.4 N.S.
55.78 55.16 **
59.68 58.84 **
57.73 57.0 **
13.56 13.36 N.S.
13.33 13.56 N.S.
13.44 13.46 N.S.
Phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
104.7 110.1 **
109.0 112.9 **
106.8 111.5 **
54.59 56.34 N.S.
56.13 62.39 **
55.36 59.37 **
13.54 13.38 *
13.84 13.06 **
13.69 13.22 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
104.7 c 107.4 b 110.0 a **
109.2 b 110.9 ab 112.7 a *
107.0 c 109.2 b 111.3 a **
51.10 b 56.92 a 58.38 a **
50.15 c 60.72 b 66.92 a **
50.63 c 58.82 b 62.65 a **
12.87 b 13.66 b 13.85 a **
12.98 c 13.44 b 13.92 a **
12.93 c 13.55 b 13.88 a **
Interactions SP SN PN
N.S. N.S. **
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
N.S. N.S. *
N.S. N.S. N.S.
N.S. N.S. **
** ** **
N.S. **(1-a) **(1-b)
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
with those obtained by Youssef et al. (2013) and Salim and Abou El-Yazied (2015), but not in accordance with those reported by El-Gizawy (2009) and Sandaña and Pinochet (2014) who reported more response to added P than that observed herein. N Level effect In both seasons and their combined, the increase of N level to 90 kg N/fad produced significant increase in plant height, flag leaf area and spike length (Table 1). Similar findings were reported by Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014) and Violeta et al. (2015), as they showed that, the increase of N level significantly increased yield attributes of wheat i.e. flag leaf area, plant height and spike length. Interaction effect Significant interaction impacts were observed to affect the spike length. According to the combined analysis, spike length was significantly affected by S N and P N interactions (Tables 1a and 1b). Regarding the spike length (Table 1a), it was significantly increased by the addition of 60 kg N/fad when wheat was grown after burned rice straw treatment, but the further increase in N level to 90 kg N/fad brought significant increase in spike length of wheat grown after rice stubble treatment. A look in Table 1a regarding this interaction effect on spike length showed linearity in the increase of spike length due to the increase of N level when wheat was grown after rice stubble treatment. The response equation predicated possible maximization of spike length to 13.85 cm due to predicated maximum additions of 51.82 kg N/fad when
wheat was grown after rice straw burning. These results clearly indicate that incorporation of rice straw residual might have had increased N immobilization and hence caused a temporary shortage of soil available nitrogen (Devlin and Witham, 1986). In otherwords, burned rice straw decreased the response of spike length to the increase of N beyond 51.82 kg N/fad, but rice straw plowing down increased its response to more than 90 kg N/fad. The spike length was also affected by the N x P interaction as shown in Table 1b. In without P application (0 kg P2O5/fad), each N increment produced a significant increase in spike length, however, in the P fertilized plots with 15.5 P2O5/fad, no significant increase in spike length could be detected beyond the addition of 60 kg N/fad. It seems possible that added P and its high level might have had made N more available to wheat plants. This effect could be physiological effect due to the role of P in enhancing root multiplication and extension and hence more root ramification and thereby more N availability for uptake. Therefore, the higher the P level, the lower N level needed to maximize spike length. Spikes number/m2 and grain number per spike.
Rice straw treatments effect Rice straw treatments had no significant effect on grain number/spike and fertile spikeletes number/spike or on sterile spikeletes number/spike in both seasons and their combined (Table 2). But, in both seasons and their combined analysis, rice straw treatments had significant effect on spikes number/m2. According to the combined analysis, differences of spikes number/m2 was significant among the two rice straw treatments, where rice stubble treatment recorded higher average than burned rice straw.
Table 1a Spike length (cm) of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (cm)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
C 12.98 a
B 13.42 a
A 13.93 a
12.97 + 0.48 x
Linear
Linear
Burned straw
B 12.87 a
A 13.68 a
A 13.83 a
12.87 + 1.14 x 0.33 x2
13.85
51.82
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
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Table 1b Spike length (cm) of wheat as affected by P level and N level interaction (combined data). Yˆ = a + bx c x2
Yˆmax (cm)
Xmax (kg N/fad)
A 14.47 a
12.92 + 0.78 x
Linear
Linear
A 13.30 b
12.93 + 0.8 x 0.31 x2
13.45
39.1
Rice straw treatments
N level 30 kg N/fad
60 kg N/fad
90 kg N/fad
0 kg P2O5/fad
C 12.92 a
B 13.68 a
15.5 kg P2O5/fad
B 12.93 a
A 13.42 a
ˆ max: predicted maximums average Xmax: predicted maximum N level. Y
Table 2 Number of spikes/m2, number of grains, fertile and sterile per spike of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
No. of spikes/m2
No. of fertile spikeletes/spike
No. of sterile spikeletes/spike
2014/ 2015
2015/ 2016
Combined
No. of grains/spike 2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
Rice straw treatments (S) Rice stubble 455.6 Burned straw 382.8 F.test **
459.1 420.6 *
457.3 401.7 **
55.63 56.73 N.S.
56.14 57.67 N.S.
55.88 57.20 N.S.
19.58 19.70 N.S.
19.76 19.57 N.S.
19.67 19.63 N.S.
2.35 2.29 N.S.
2.42 2.41 N.S.
2.38 2.35 N.S.
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
423.7 414.7 N.S.
454.3 425.3 **
439.0 420.0 **
56.03 56.33 N.S.
59.61 54.20 **
57.82 55.27 **
19.48 19.80 **
19.79 19.53 *
19.63 19.67 N.S.
2.22 2.42 **
2.18 2.64 **
2.20 2.53 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
405.7 b 424.8 a 427.0 a **
424.2 b 451.0 a 444.3 a **
415.0 b 437.9 a 435.7 a **
52.01 b 59.68 a 56.85 a **
52.84 b 59.22 a 58.65 a **
52.43 b 59.45 a 57.75 a **
19.47 19.63 19.82 N.S.
19.33 b 19.37 b 20.28 a **
19.40 b 19.50 b 20.05 a **
2.62 a 2.26 b 2.09 c **
2.68 a 2.69 a 1.86 b **
2.65 a 2.48 b 1.98 c **
Interactions SxP SxN PxN
N.S. N.S. N.S.
** * N.S.
*(2-a) N.S. N.S.
N.S. N.S. N.S.
* ** N.S.
N.S. **(2-b) N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. *
N.S. N.S. N.S.
N.S. **(2-c) N.S.
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
P Level effect In the second season and the combined analysis, the increase of P level to 15.5 P2O5/fad produced significant decrease in spikes number/m2 and grain number/spike (Table 2). Similar significant effect was observed in fertile spikeletes number/spike in the second season, but in the first season, the fertile spikeletes number/ spike was significantly increased due to the increase of P level. However, in both seasons and the combined analysis significant increase in sterile spikeletes number/spike was decked due to the addition of P level. The decrease of the number of spikes/m2 due to the addition of P (15.5 P2O5/fad) needs to be clarified. The possibility of nutrient imbalance caused by added P to possibly micronutrients and in particular Zn cannot be neglected. The soil of the experimental was poor in almost all micronutrients where a more uptake of P might have had decreased the uptake one or more of these micronutrients (Miller and Donahue, 1990). This in turn was on the expense of effective tillering where the number of spikes/m2 was decreased, though the plant height was increased (Table 1). These results are not in accordance with those reported by El-Gizawy (2009), Youssef et al. (2013), Salim and Abou ElYazied (2015) and Ram et al. (2015) who reported that increasing P levels significantly increase the yield and yield attributes of wheat.
of N level to 90 kg N/fad produced significant increase in the fertile spikeletes number/spike in the second season and the combined analysis. However, the increase of N level to 90 kg N/fad produced significant decrease in sterile spikeletes number/spike in the both seasons and their combined analysis (Table 2). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014) and Violeta et al. (2015). Interaction effect Significant interaction effects were observed to affect both spikes number/m2, grain number/spike and sterile spikeletes number/spike. Regarding spikes number/m2 (Table 2a) it was significantly decreased by addition of 15.5 P2O5/fad when removal rice straw (rice stubble treatment), but significantly increased when addition of 15.5 P2O5/fad with burning rice straw. A look in the soil analysis showed that experimental soil was moderate in organic matter content (1.03%) and hence, this might play an important
Table 2a Number of spikes/m2 of wheat as affected by rice straw treatments and P level interaction (combined data). Rice straw treatments
N Level effect Rice stubble
In both seasons and their combined analysis, the increase of N level up to 60 kg N/fad was followed by a significant increase in spikes number/m2 and grain number/spike. While, the increase
Burned straw
P level Check
15.5 kg P2O5/fad
A 492.0 a B 386.0 b
B 422.7 a A 417.3 a
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role in availability of micronutrient elements. Addition of P fertilizer under these conditions could reflected an antagonistic effect caused probably by different chelating interaction effects and hence had made P unavailable and caused significant decreased in spikes number/m2. Grain number/spike was affected by the rice straw treatments x N interaction as shown in Table 2b. In the rice straw treatments plots, the increase of N level up to 60 kg N/fad produced a significant increase in grain number/spike where the response equations detected only 58.30 kg N/fad needed to maximize the grain number of spike to 53.29 grain when removal of rice straw compared with 35.22 kg N/fad needed to maximize this number to 61.96 grain when burning rice straw. It is evident from Table 2c that the sterile spikeletes number/spike was significantly decreased due to the increase of N level in rice straw treatments and showed linearity. Grain weight per spike and 1000-grain weight.
et al. (2013) and Violeta et al. (2015). However, the results were not in accordance with those reported by Mekail et al. (2006), Abdul Galil et al. (2008) and Khalid et al. (2014) who reported significant increase in 1000-grain weight due to increase of N level. Interaction effect None of the first order interactions affected significantly the grain weight per spike and 1000-grain weight in the combined analysis (Table 3). This clearly indicated the independence of the main effects of these factors in affecting wheat yield. It was evident that N fertilization level played the major role in affecting yield attributes of wheat. Wheat yields/fad and harvest index. Rice straw treatments effect
Rice straw treatments effect Rice straw treatments had no significant effect on grain weight per spike in both seasons and their combined. However, in the second season and the combined of both seasons, rice straw treatments had significant effect on 1000-grain weight (Table 3). It is evident from Table 3 that the rice straw plowing down treatment recorded heavier 1000-grain weight than burned rice straw treatment. It seems possible that burning rice straw was followed by gaseous losses of N as well as some of elements as P, K, S, Ca, Mg (Ponnamperuma, 1984; Lefroy et al., 1994; Dobermann and Fairhurst, 2002 and Dobermann and Witt, 2000) and hence a possible decrease in soil available nutrients. So, this might have had caused decreased in soil fertility and therefore reflected the decrease in 1000-grain weight. P Level effect The addition of 15.5 P2O5/fad gave significant increase in grain weight per spike and 1000-grain weight though, the grain weight per spike was not significantly increased by this addition in the second season (Table 3). These results are in harmony with those obtained by El-Gizawy (2009), Youssef et al. (2013), Sandaña and Pinochet (2014) and Salim and Abou El-Yazied (2015).
It is evident from Table 4 that, the burning of rice straw recorded lower grain, straw and total yields/fad than the rice straw plowing down treatment. However, the harvest index was increased due to rice straw burning. The decrease of grain yield/fad due rice straw burning was also observed in the number of spikes/ m2 and 1000-grain weight and could account for the decrease observed herein. It seems possible that burning rice straw was followed by losses of NPK and hence a possible decrease in soil fertility (Dobermann and Fairhurst, 2002). P Level effect In both seasons and their combined, the addition of 15.5 P2O5/fad was followed by a significant decrease in grain yield/fad and harvest index as well as the total yield/fad in the combined analysis of both seasons. But, in the second season, this addition was followed by a significant increase in straw yield/fad (Table 4). These results indicate the increase observed in plant height, flag leaf area, grain weight per spike, 1000-grain weight due to P addition was not reflected in grain or total yields/fad and harvest index. These results are not in accordance with those reported by El-Gizawy (2009), Lehoczkyb et al. (2012), Youssef et al. (2013) and Srivatsava et al. (2015) as they reported that, increasing P levels significantly increase of yield and yield attributes of wheat.
N Level effect N Level effect In both seasons and their combined, the increase of N level to 60 kg N/fad produced a significant increase in grain weight per spike, while further increase in N level did not add a further significant increase. However, each increase of N level to 60 or 90 kg N/fad produced at par significant decrease in 1000-grain weight in the first season and the combined of both seasons (Table 3). These results clearly indicate the 60 kg N/fad were enough to increase the grain weight/spike as previously observed in the number of grains/ spike (Table 2). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Youssef
The increase of N level up to 90 kg N/fad gave significant increase in grain and total yields/fad and harvest index. The straw yield/fad was increased due to the first N increment but no further increase was observed due to the second N increment (Table 4). These results are rather expected as almost the yield attributes were increased due to increase in N level. This favorable effect of N may be due its effective role in many biochemical processes in plants (Miller and Donahue, 1990). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al.
Table 2b Number of grains per spike of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (No.)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
B 52.30 a
A 57.15 b
A 58.20 a
52.3 + 6.75 x 1.9 x2
58.3
53.29
Burned straw
B 52.55 a
A 61.75 a
A 57.30 a
52.55 + 16.03 x 6.83 x2
61.96
35.22
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
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Table 2c Number of sterile spikeletes per spike of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (No.)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
A 2.70 a
A 2.55 a
B 1.90 a
2.78 0.40 x
Linear
Linear
Burned straw
A 2.60 a
A 2.40 a
B 2.05 a
2.63 0.28 x
Linear
Linear
ˆ max: predicted maximums average Xmax: predicted maximum N level. Y
Table 3 Grain weight per spike and 1000-grain weight of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
Grain weight per spike (g)
1000-grain weight (g)
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
Rice straw treatments (S) Rice stubble Burned straw F.test
2.56 2.59 N.S.
2.66 2.56 N.S.
2.61 2.58 N.S.
47.75 47.04 N.S.
47.57 44.72 *
47.66 45.87 **
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
2.48 2.67 **
2.61 2.61 N.S.
2.54 2.64 *
45.83 48.96 **
43.36 48.91 **
44.60 48.93 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
2.31 b 2.67 a 2.75 a **
2.42 b 2.75 a 2.66 a **
2.36 b 2.70 a 2.70 a **
49.86 a 47.58 b 44.74 c **
47.37 a 45.95 b 45.09 b **
48.62 a 46.77 b 44.92 c **
Interactions SxP SxN PxN
N.S. ** **
N.S. N.S. N.S.
N.S. N.S. N.S.
** N.S. **
N.S. * N.S.
N.S. N.S. N.S.
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
Table 4 Grain, straw, total yields and harvest index of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in the two seasons. Main effects and interactions
Grain yield (ton/fad) 2014/ 2015
Straw yield (ton/fad)
Total yield (ton/fad)
Harvest index (%)
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
Rice straw treatments (S) Rice stubble 3.17 Burned straw 3.01 F.test *
3.06 3.03 N.S.
3.12 3.02 **
6.48 5.97 **
6.51 6.13 **
6.49 6.05 **
9.65 8.98 **
9.57 9.16 **
9.61 9.07 **
32.85 33.52 N.S.
31.97 33.08 **
32.41 33.30 **
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
3.17 3.01 **
3.23 2.87 **
3.20 2.94 **
6.23 6.22 N.S.
6.19 6.44 *
6.21 6.33 N.S.
9.40 9.23 N.S.
9.42 9.31 N.S.
9.41 9.27 *
33.72 32.61 **
34.29 30.83 **
34.01 31.72 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
2.88 c 3.07 b 3.32 a **
2.68 c 3.01 b 3.45 a **
2.78 c 3.04 b 3.39 a **
6.27 6.25 6.16 N.S.
6.12 b 6.35 ab 6.49 a *
6.19 6.30 6.33 N.S.
9.15 b 9.32 ab 9.48 a *
8.80 c 9.36 b 9.94 a **
8.98 c 9.34 b 9.71 a **
31.48 c 32.94 b 35.02 a **
30.45 c 32.16 b 34.71 a **
30.97 c 32.55 b 34.86 a **
Interactions SxP SxN PxN
N.S. N.S. N.S.
N.S. ** **
N.S. **(4-a) **(4-b)
N.S. ** N.S.
** N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
** N.S. N.S.
N.S. N.S. N.S.
*,**and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
(2010), Lehoczkyb et al. (2012), Youssef et al. (2013), Srivatsava et al. (2015) and Bhatt et al. (2016).
Interaction effect The combined analysis indicated clear significant interaction effect between rice straw treatments and N levels as observed in
grain yield per fad (Table 4a). It is quite evident from Table 4a that the grain yield/fad was not significantly increased unless 90 kg N/fad was added in rice stubble treatment where rice straw was plowed down before sowing. In the burned rice straw plots, each N increase was followed by a significant increase in grain yield/fad but this increase was diminishing. The response equation detected the possibility of maximizing the grain yield/fad to 3.73 ton/fad if
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E.E.A. El-Sobky / Ann. Agric. Sci. 62 (2017) 113–120 Table 4a Grain yield (ton/fad) of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
Yˆ = a + bx c x2
ˆ max (ton/fad) Y
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
B 2.96 a
B 3.02 a
A 3.37 a
2.91 + 0.21 x
Linear
Linear
Burned straw
C 2.60 b
B 3.06 a
A 3.40 a
2.6 + 0.52 x 0.06 x2
3.73
130
Yˆ = a + bx c x2
ˆ max (ton/fad) Y
Xmax (kg N/fad)
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
Table 4b Grain yield (ton/fad) of wheat as affected by P level and N level interaction (combined data). Rice straw treatments
N level 30 kg N/fad
60 kg N/fad
90 kg N/fad
0 kg P2O5/fad
B 2.92 a
B 3.09 a
A 3.58 a
2.87 + 0.33 x
Linear
Linear
15.5 kg P2O5/fad
C 2.64 b
B 2.98 b
A 3.19 b
2.64 + 0.41 x 0.06 x2
3.27
93.46
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
the N level was increased to 130 kg N/fad instead of 3.40 ton/fad obtained due to the addition of 90 kg N/fad. Also, grain yield/fad was affected by the N P interaction as shown in Table 4b. In without P application (0 kg P2O5/fad), no significant increase in grain yield/fad could be detected beyond the addition of 60 kg N/fad. However, in the P fertilized plots with 15.5 P2O5/fad, each increase of N level up to 90 kg N/fad was followed by a significant increase in grain yield/fad. Conclusion The present study was carried out seeking answers for the following questions: Is there any benefit from burning rice straw for the soil fertility and hence yield of the succeeding crop i.e. wheat? Does the addition of mineral N help in speeding up N mineralization and hence the immediate release of NO3 for wheat as well as reduced adverse effects of rice straw burning? Burning of rice straw had significant adverse effect on the grain yield, though this significant effect was observed on some yield attributes as flag leaf area, number of spikes/m2 and 1000-grain weight which is known to have a great contribution to yield variation in wheat. While, the soil incorporation of rice straw had more significant favorable effect on the grain yield and some yield attributes where, rice straw incorporation as a practice of organic manuring, might help in partly solving defects of rice straw burning. On other hand, due to the wide C:N ratio (57:1) of rice straw, a temporary drop of the soil mineral N content, addition of N fertilizer under these conditions could possibly increase gained benefits through enriching soil fertility from a rapid release of available nitrogen. Also, addition of P fertilizer might have had caused improving in soil fertility therefore, reflected on increase in yield and yield attributes of wheat. References A.O.A.C., 2000. Official Methods of Analytical of Association of Official Analysis. Agriculture chemists 17th ed. Washington, N.S.A. Abdel Nour, N.A.R., Fateh, H.S.A., 2011. Influence of sowing date and nitrogen fertilization on yield and its components in some bread wheat genotypes. Egypt. J. Agric. Res. 89 (4), 1413–1433. Abdul Galil, A.A., Basha, H.A., Mowafy, S.A., Mohamed, S.M., 2008. Effect of N level and splitting different levels of P on yield of two wheat cultivars and p use efficiency attributes using sprinkler irrigation system in sandy soil. Minufiya J. Agric. Res. 33 (3), 741–775.
Abdul Galil, A.A., Basha, H.A., Mowafy, S.A.E., Mohamed, S.M., 2003. Effect of phosphorus addition on the response of four wheat cultivars to N fertilization level under sandy soil conditions. Minufiya J. Agric. Res. 28 (1), 1–22. Amal, H.E., Omran, S.E.H., El-Fiki, S.F., 2005. Response of Gemmiza 7 wheat cultivar to different levels of nitrogen and zinc fertilization. Minufiy J. Agric. Res. 30 (2), 791–799. Bakker, R., Elbersen, W., Poppens, R., Lesschen, J.P., 2013. Rice straw and wheat straw, potential feedstocks for the biobased economy, NL Energy and Climate Change 1–31, The Netherlands. Bhatt, B., Chandra, R., Ram, S., Pareek, N., 2016. Long-term effects of fertilization and manuring on productivity and soil biological properties under rice (Oryza sativa)–wheat (Triticum aestivum) sequence in Mollisols. Arch. Agron. Soil Sci. 62, 1109–1122. Black, C.A., 1982. Methods of Soil Analysis, Part2 American Society of Agronomy. Inc. Publisher, Madison, Wisconsin, USA. Devlin, R.M., Witham, F.H., 1986. Plant Physiology. 4th Ed. CBS publishers and distributors 485, Jain Bhawan, Shadhara, Delhi, India. Diacono, M., Rubino, P., Montemurro, F., 2013. Precision nitrogen management of wheat a review. Agron. Sustain. Dev. 33 (1), 219–241. Dobermann, A., Fairhurst, T.H., 2002. Rice Straw Management. Better Crops International 16:1–11. May, Special Supplement. Dobermann, A., Witt, C., 2000. The potential impact of cropintensification on carbon and nitrogen cycling in intensive rice systems. Int. Rice Res. Inst., Los Baños, Philippines, 1–25. Duncan, D.B., 1955. Multiple range and multiple ‘‘F” test. Biometrics 11, 1–42. El-Gizawy, N.K.B., 2009. Effect of planting date and fertilizer application on yield of wheat under no till system. World J. Agric. Sci. 5 (6), 777–783. FAOSTAT, 2017. Food and Agricultural Organization of the United Nations (FAO), FAO Statistical Database,. Gomez, K.N., Gomez, A. A., 1984. Statistical Procedures for Agricultural Res., second ed. John Wiley and Sons, New York, 68. Khalid, M., Ali, M.F.S., Pervez, M.W., Rehman, M., Hussain, S., Rehman, K., 2014. Optimization of nitrogen fertilizer level for newly evolved wheat (Triticum aestivum) cultivars. App. Sci. Report 3 (2), 83–87. Lal, K.N., Subba Rao, M.S., 1951. A rapid method for flag leaf area determination. Nature 167, 72. Lefroy, R.D.B., Chaitep, W., Blair, G.J., 1994. Release of sulfur from rice residues under flooded and non-flooded soil conditions. Aust. J. Agric. Res. 45, 657–667. Lehoczkyb, É., Kismányokya, A., Lencse, T., Németh, T., 2012. Effect of different fertilization methods and nitrogen doses on the weediness of winter wheat. Commun. Soil Sci. Plant Anal. 43, 341–345. Mahrous, N.M., Mahrous, A.M.S, Sadek, J.G., Shaban, K.A., 2010. Improving wheat production and grain quality by inorganic, organic and some micronutrients fertilizers under saline condition. Res. J. Agric. Biol. Sci. 6 (6), 1087–1098. Mekail, M.M., Hassan, H.A., Mohamed, W.S., Telep, A.M., Abd El-Azeim, M.M., 2006. Integrated supply system of nitrogen for wheat grown in the newly reclaimed sandy soils of west El-Minia: efficiency and economics of the system. Minia J. Agric. Res. Dev. 26(1), 101–130. Miller, R.W., Donahue, R.L., 1990. Soils: An Introduction to Soils and Plant Growth. Prentice-Hall Inc., USA. MSTAT-C, 1991. A Microcomputer Program for the Design, Management and Analysis of Agronomic Research Experiment. MSTAT Development Team, Michign State University. Neter, J., Wasserman, W., Kutner, M.H., 1990. Applied Liner Statistical Model. IRWIN, Boston, MA, USA.
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Ponnamperuma, F.N., 1984. Straw as a source of nitrogen for wetland rice. In: Banta, S., Mandoza, C.V. (Eds.), Organic Matter and Rice. IRRI, Los Banos, Philippines, pp. 117–136. Ram, H., Malik, S.S., Dhaliwal, S.S., Kumar, B., Singh, Y., 2015. Growth and productivity of wheat affected by phosphorus-solubilizing fungi and phosphorus levels. Plant Soil Environ. 61 (3), 122–126. Rana, A., Joshi, M., Prasanna, R., Shivay, Y.S., Nain, L., 2012. Biofortification of wheat through inoculation of plant growth promoting rhizobacteria and cyanobacteria. Eur. J. Soil Biol. 50, 118–126. Salim, B.B.M., Abou El-Yazied, A., 2015. Effect of bio-NP fertilizer and different doses of mineral N and P fertilizers on growth, yield productivity and some biochemical constituents of wheat, faba bean and onion plants. Middle East J. Appl. Sci. 5, 965–974. Sandaña, P., Pinochet, D., 2014. Grain yield and phosphorus use efficiency of wheat and pea in a high yielding environment. J. Soil Sci. Plant Nutr. 14 (4), 973–986.
Snedecor, G.W., Cochran, W.G., 1967. Statistical Methods. Iowa State Univ. Press, Iowa, USA. Srivatsava, P.K., Maruthi Sankar, G.R., Vijaya Kumar, P., Singh, S.P., Rani, N., Singh, A., Agarwal, V.K., 2015. Effects of Organic and inorganic fertilizers on soil and plant nutrients and yields of pearl millet and wheat under semi-arid inceptisols in India. Commun. Soil Sci. Plant Anal. 46, 2595–2614. Violeta, M., Krnjaja, V., Tomic, Z., Bijelic, Z., Simic, A., Muslic, D.R., Gogic, M., 2015. Nitrogen fertilizer influence on wheat yield and use efficiency under different environmental conditions. Chilean J. Agric. Res. 75 (1), 92–97. Weber, E.A., Graeff, S., Koller, W.D., Hermann, W., Merkt, N., Claupein, W., 2008. Impact of nitrogen amount and timing on the potential of acrylamide formation in winter wheat (Triticum aestivum L.). Field Crops Res. 106, 44–52. Youssef, S.M., Faizy, S.E.D., Mashali, S.A., El-Ramady, H.R., Ragab, S., 2013. Effect of different levels of NPK on wheat crop in North Delta. Jahrestagung der Deutschen Bodenkundlichen Gesellschaft vom 07. bis12. September in Rostock; Vorträge Kommission IV.
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Effect of burned rice straw, phosphorus and nitrogen fertilization on wheat (Triticum aestivum L.) El-Sayed E.A. El-Sobky Agronomy Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt
a r t i c l e
i n f o
Article history: Received 23 February 2017 Received in revised form 18 May 2017 Accepted 21 May 2017 Available online 7 June 2017 Keywords: Wheat Rice straw Phosphorus Nitrogen Yield attributes
a b s t r a c t This investigation was carried out in the Experimental Farm at Ghazala Village (Faculty of Agriculture, Zagazig University, Egypt) during two successive seasons (2014/2015 and 2015/2016) to study the effect of rice straw burning (rice straw plowing down and rice straw burning), phosphorus (P) level (0 and 15.5 kg P2O5/fad [fad = faddan = 4200 m2 and ha = 2.38 fad]), and nitrogen (N) level (30, 60 and 90 kg N/fad) on wheat (Triticum aestivum L. cv. Gemmiza 11). Burned rice straw significantly decreased the flag leaf area, spikes number/m2, 1000-grain weight, grain and total yields/fad. The increase of P level to 15.5 kg P2O5/fad produced significant increase in plant height, flag leaf area, grain weight per spike, 1000-grain weight but, decreased the number of spikes/m2 and the grain yield/fad and harvest index. The increase of N level up to 90 kg N/fad gave significant increase in grain yield and yield attributes except the number of sterile spikeletes/spike and 1000-grain weight which were decreased. Ó 2017 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-ncnd/4.0/).
Introduction Rice (Oryzae sativa L.) is an important cereal crop which ranks the second after wheat in Egypt where cultivated area reached 1.37 million fad (FAOSTAT, 2017). Rice farmer have got used to burn rice straw as they believe in some gained benefits to their soil fertility or as a measure of controlling pest damage. They found burning is the cheapest and easiest way for removing large loads of the produced rice straw. Also, burning of straw is mainly caused by the need of a short turnover time between rice and following crops. The next crop (wheat or other crops) will have the highest yields when this crop can be established as early in the autumn period as possible, thereby benefiting from higher temperatures and longer days as well as, it much easier to prepare a seedbed for the following crop. There are various options for incorporating the straw into the field as alternative for burning but these options generally require mechanization, water, and additional fertilizer in order for rice straw to quickly decompose in the field. In addition, the degradation of straw may also lead to significant emissions of gases, such as methane (Bakker et al., 2013). Due to the large rice cultivated area during the last decades, burning rice straw has become one of the main sources to air pollution, where the large losses going into the atmosphere up to 80% of N (Dobermann
and Witt, 2000 and Dobermann and Fairhurst, 2002), 25% of P and 21% of potassium (K) (Ponnamperuma, 1984), 4–60% of sulphur (S) (Lefroy et al., 1994) are reported. Addition of P and N fertilizers under these conditions could possibly increase gained benefits through enriching soil fertility. Several authors reported significant increase of grain yield and yield attributes due to the addition of P fertilizer up to 45, 22, 15.5 and 11 kg P2O5/fad as reported by El-Gizawy (2009), Youssef et al. (2013), Salim and Abou El-Yazied (2015) and Ram et al. (2015). Also, Lehoczkyb et al. (2012) and Sandaña and Pinochet (2014) showed that, the increase P levels up to 42 and 105 kg P2O5/fad increased wheat grain yield, biomass and its components. Nitrogen is an essential nutrient for plant growth and development being involved in vital plant functions such as photosynthesis, DNA synthesis, protein formation and respiration (Rana et al., 2012 and Diacono et al., 2013). Many studies revealed that, the increase of N levels significantly increased yield and yield attributes of wheat i.e. number of spikes/m2, flag leaf area, plant height, spike length, number of spikeletes and grains/spike, 1000-grain weight due to the addition of N fertilizer up to 90, 75.5, 100, 75, 80, 42, 63 and 50 kg N/fad as reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014), Violeta et al. (2015) and Bhatt et al. (2016).
Peer review under responsibility of Faculty of Agriculture, Ain-Shams University. E-mail address: [email protected] http://dx.doi.org/10.1016/j.aoas.2017.05.007 0570-1783/Ó 2017 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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Therefore, the present study aimed to investigate the effect of burning of rice straw on the growth and yield of wheat under different levels of P and N fertilization. Materials and methods The present study was conceded at Ghazala Village, Fac. of Agric., Zagazig Univ., Sharkia Governorate, Egypt (30.11°N, 31.41°E) during two successive seasons (2014/2015 and 2015/2016) of wheat plant in a clay soil. For soil properties, soil samples were collected from the experimental sites at the depth of 0–30 cm before planting to determine soil physical and chemical properties according to Black (1982). Soil analysis showed that soil had clay in texture having 20.61% sand, 31.82% silt, 47.57% clay, 1.03% organic matter and C: N ratio of 12:1. It had of total N 0.05%, available P of 8.15 ppm, available K of 149.3 ppm, available Fe of 1.75 ppm, available Zn of 0.51 ppm, available Mn of 0.31 ppm and 8.02 pH (Moderately alkaline) as averages of both seasons. The atomic absorption spectrophotometer was used to determine Zn, Fe and Mn. Moreover, rice straw was determined according to A. O.A.C. (2000) where rice straw analysis showed that it had having 0.39% Total N, 310 ppm available P, 38% organic matter and C: N ratio of 57: 1, as averages of both seasons. Wheat (Triticum aestivum L. cv. Gemmiza 11) was sown in the last week of November in the two seasons. Sowing was made in rows 15 cm apart. Each 2nd order sub plot included 20 rows of 3 m length (9 m2). Sowing was made after rice as a preceding crop in both seasons using seeding rates of 70 kg/fad. Flood irrigation was practiced in one month interval and was withheld one month before harvest which was made during the last week of April. Studied Factors A: Rice straw treatments: 1. Rice stubble: The stubble of rice i.e. residues was plowed down as recommended before sowing wheat. 2. Burned rice straw before sowing wheat. An average straw yield of 6 ton/fad of the preceding rice crop was burned and plowed down at the depth of 30 cm before seedbed preparation for wheat. B: Phosphorus fertilization levels: 1. 0 kg P2O5/fad: Without P fertilization. 2. 15.5 kg P2O5/fad: P at a level of 15.5 kg P2O5/fad as ordinary superphosphate (15.5% P2O5) was band placed at the time of sowing. C: Nitrogen fertilization levels: 1. 30 kg N/fad. 2. 60 kg N/fad. 3. 90 kg N/fad. One fifth of N fertilization levels was added as basal dose before sowing wheat as ammonium sulphate (20.5%). The rest of these two N levels was split and partly added before the first and second irrigations as ammonium nitrate (33.5% N). Plots were surrounded by wide borders (0.75 m) to prevent movement of nutrients from fertilized to non-fertilized plots. Experimental design: A split-split plot design of four replications was used, where the rice straw treatments were allocated in the main plots. P and N fertilization levels were allocated in the first and second (9 m2) order subplots, respectively. Vegetative parameters: At heading, ten guarded plants were taken at random from each experimental plot to determine plant
height (cm) and flag leaf area (cm2) which was determined according Lal and Subba Rao (1951) by using blade length maximum blade width 0.72. Reproductive parameters: Number of spikes/m2 (recorded from 1 m2 using a wooden square). A bordered area of 1.0 m length (0.15 m2), previously labeled in the other 3rd row after emergence (10 days after sowing), was harvested where the following yield and yield attributes were recorded on 10 plants: plant height (cm), spike length (cm), number of fertile and sterile spikeletes/ spike, number of grains/spike, grain weight/spike (g), 1000-grain weight (g). The grain, straw and total yields (ton/fad) were calculated using the yields obtained from 1.0 m2 and harvest index (%) i.e., grain to total yield in percentage. Statistical analysis Data were statistically analyzed according to Gomez and Gomez (1984) by using MSTAT-C (1991) where statistical program Version 2.1 was used for analysis of variance (ANOVA). Duncan Multiple range test was used to compare statistical significant differences (Duncan, 1955). In interaction tables, capital and small letters were used to denote significant differences among rows and columns ˆ max) means, respectively. The predicated maximum trait average (Y which could have been obtained due to the addition of the predicted maximum N level (Xmax) are also included. The response equations were calculated according to Snedecor and Cochran (1967) using the orthogonal polynomial tables. The significancy of the linear and quadratic components of each of these equations was tested, then the response could be described as linear (first order) or quadratic (second order). The predicted maximum averˆ max) which could have been obtained due to the addition ages (Y of the predicted maximum N level (Xmax) were calculated according to Neter et al. (1990) as explained by Abdul Galil et al. (2003) using the following equations:
^ max ¼ Y ^ 0 þ b2 =4c Y
Xmax ¼ X0 þ b=2cðuÞ
where Yˆ0 = Grain yield at the lowest N level i.e. zero kg N/fad (ton/fad). b = Measures the linear component of the response equation. c = Measures the quadratic component of the response equation. u = unit of N = 30 kg N/fad. Results and discussion Plant height, flag leaf area and spike length. Rice straw treatments effect Plant height and spike length were not significantly affected by rice straw treatments in both seasons and their combined. However, flag leaf area of wheat grown after rice straw burning was decreased (Table 1). These results clearly indicate that burning of rice straw causes almost complete N loss, P losses of about 25%, K losses of 21%, and S losses of 4–60% (Ponnamperuma, 1984; Lefroy et al., 1994 and Dobermann and Fairhurst, 2002) and hence caused shortage of soil available nutrients and therefore reflected the decrease in wheat flag leaf area. P Level effect In both seasons and their combined, the increase of P level to 15.5 kg P2O5/fad produced significant increase in plant height, which was also observed in flag leaf area in the second season and the combined analysis (Table 1). However, spike length was decreased due to addition P (15.5 kg P2O5/fad) compared with without P application (0 kg P2O5/fad). These results are in harmony
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Table 1 Plant height, flag leaf area and spike length of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
Flag leaf area (cm2)
Plant height (cm)
Spike length (cm)
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
Rice straw treatments (S) Rice stubble Burned straw F.test
104.5 110.3 N.S.
111.4 110.5 N.S.
107.9 110.4 N.S.
55.78 55.16 **
59.68 58.84 **
57.73 57.0 **
13.56 13.36 N.S.
13.33 13.56 N.S.
13.44 13.46 N.S.
Phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
104.7 110.1 **
109.0 112.9 **
106.8 111.5 **
54.59 56.34 N.S.
56.13 62.39 **
55.36 59.37 **
13.54 13.38 *
13.84 13.06 **
13.69 13.22 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
104.7 c 107.4 b 110.0 a **
109.2 b 110.9 ab 112.7 a *
107.0 c 109.2 b 111.3 a **
51.10 b 56.92 a 58.38 a **
50.15 c 60.72 b 66.92 a **
50.63 c 58.82 b 62.65 a **
12.87 b 13.66 b 13.85 a **
12.98 c 13.44 b 13.92 a **
12.93 c 13.55 b 13.88 a **
Interactions SP SN PN
N.S. N.S. **
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
N.S. N.S. *
N.S. N.S. N.S.
N.S. N.S. **
** ** **
N.S. **(1-a) **(1-b)
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
with those obtained by Youssef et al. (2013) and Salim and Abou El-Yazied (2015), but not in accordance with those reported by El-Gizawy (2009) and Sandaña and Pinochet (2014) who reported more response to added P than that observed herein. N Level effect In both seasons and their combined, the increase of N level to 90 kg N/fad produced significant increase in plant height, flag leaf area and spike length (Table 1). Similar findings were reported by Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014) and Violeta et al. (2015), as they showed that, the increase of N level significantly increased yield attributes of wheat i.e. flag leaf area, plant height and spike length. Interaction effect Significant interaction impacts were observed to affect the spike length. According to the combined analysis, spike length was significantly affected by S N and P N interactions (Tables 1a and 1b). Regarding the spike length (Table 1a), it was significantly increased by the addition of 60 kg N/fad when wheat was grown after burned rice straw treatment, but the further increase in N level to 90 kg N/fad brought significant increase in spike length of wheat grown after rice stubble treatment. A look in Table 1a regarding this interaction effect on spike length showed linearity in the increase of spike length due to the increase of N level when wheat was grown after rice stubble treatment. The response equation predicated possible maximization of spike length to 13.85 cm due to predicated maximum additions of 51.82 kg N/fad when
wheat was grown after rice straw burning. These results clearly indicate that incorporation of rice straw residual might have had increased N immobilization and hence caused a temporary shortage of soil available nitrogen (Devlin and Witham, 1986). In otherwords, burned rice straw decreased the response of spike length to the increase of N beyond 51.82 kg N/fad, but rice straw plowing down increased its response to more than 90 kg N/fad. The spike length was also affected by the N x P interaction as shown in Table 1b. In without P application (0 kg P2O5/fad), each N increment produced a significant increase in spike length, however, in the P fertilized plots with 15.5 P2O5/fad, no significant increase in spike length could be detected beyond the addition of 60 kg N/fad. It seems possible that added P and its high level might have had made N more available to wheat plants. This effect could be physiological effect due to the role of P in enhancing root multiplication and extension and hence more root ramification and thereby more N availability for uptake. Therefore, the higher the P level, the lower N level needed to maximize spike length. Spikes number/m2 and grain number per spike.
Rice straw treatments effect Rice straw treatments had no significant effect on grain number/spike and fertile spikeletes number/spike or on sterile spikeletes number/spike in both seasons and their combined (Table 2). But, in both seasons and their combined analysis, rice straw treatments had significant effect on spikes number/m2. According to the combined analysis, differences of spikes number/m2 was significant among the two rice straw treatments, where rice stubble treatment recorded higher average than burned rice straw.
Table 1a Spike length (cm) of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (cm)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
C 12.98 a
B 13.42 a
A 13.93 a
12.97 + 0.48 x
Linear
Linear
Burned straw
B 12.87 a
A 13.68 a
A 13.83 a
12.87 + 1.14 x 0.33 x2
13.85
51.82
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
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Table 1b Spike length (cm) of wheat as affected by P level and N level interaction (combined data). Yˆ = a + bx c x2
Yˆmax (cm)
Xmax (kg N/fad)
A 14.47 a
12.92 + 0.78 x
Linear
Linear
A 13.30 b
12.93 + 0.8 x 0.31 x2
13.45
39.1
Rice straw treatments
N level 30 kg N/fad
60 kg N/fad
90 kg N/fad
0 kg P2O5/fad
C 12.92 a
B 13.68 a
15.5 kg P2O5/fad
B 12.93 a
A 13.42 a
ˆ max: predicted maximums average Xmax: predicted maximum N level. Y
Table 2 Number of spikes/m2, number of grains, fertile and sterile per spike of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
No. of spikes/m2
No. of fertile spikeletes/spike
No. of sterile spikeletes/spike
2014/ 2015
2015/ 2016
Combined
No. of grains/spike 2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
Rice straw treatments (S) Rice stubble 455.6 Burned straw 382.8 F.test **
459.1 420.6 *
457.3 401.7 **
55.63 56.73 N.S.
56.14 57.67 N.S.
55.88 57.20 N.S.
19.58 19.70 N.S.
19.76 19.57 N.S.
19.67 19.63 N.S.
2.35 2.29 N.S.
2.42 2.41 N.S.
2.38 2.35 N.S.
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
423.7 414.7 N.S.
454.3 425.3 **
439.0 420.0 **
56.03 56.33 N.S.
59.61 54.20 **
57.82 55.27 **
19.48 19.80 **
19.79 19.53 *
19.63 19.67 N.S.
2.22 2.42 **
2.18 2.64 **
2.20 2.53 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
405.7 b 424.8 a 427.0 a **
424.2 b 451.0 a 444.3 a **
415.0 b 437.9 a 435.7 a **
52.01 b 59.68 a 56.85 a **
52.84 b 59.22 a 58.65 a **
52.43 b 59.45 a 57.75 a **
19.47 19.63 19.82 N.S.
19.33 b 19.37 b 20.28 a **
19.40 b 19.50 b 20.05 a **
2.62 a 2.26 b 2.09 c **
2.68 a 2.69 a 1.86 b **
2.65 a 2.48 b 1.98 c **
Interactions SxP SxN PxN
N.S. N.S. N.S.
** * N.S.
*(2-a) N.S. N.S.
N.S. N.S. N.S.
* ** N.S.
N.S. **(2-b) N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. *
N.S. N.S. N.S.
N.S. **(2-c) N.S.
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
P Level effect In the second season and the combined analysis, the increase of P level to 15.5 P2O5/fad produced significant decrease in spikes number/m2 and grain number/spike (Table 2). Similar significant effect was observed in fertile spikeletes number/spike in the second season, but in the first season, the fertile spikeletes number/ spike was significantly increased due to the increase of P level. However, in both seasons and the combined analysis significant increase in sterile spikeletes number/spike was decked due to the addition of P level. The decrease of the number of spikes/m2 due to the addition of P (15.5 P2O5/fad) needs to be clarified. The possibility of nutrient imbalance caused by added P to possibly micronutrients and in particular Zn cannot be neglected. The soil of the experimental was poor in almost all micronutrients where a more uptake of P might have had decreased the uptake one or more of these micronutrients (Miller and Donahue, 1990). This in turn was on the expense of effective tillering where the number of spikes/m2 was decreased, though the plant height was increased (Table 1). These results are not in accordance with those reported by El-Gizawy (2009), Youssef et al. (2013), Salim and Abou ElYazied (2015) and Ram et al. (2015) who reported that increasing P levels significantly increase the yield and yield attributes of wheat.
of N level to 90 kg N/fad produced significant increase in the fertile spikeletes number/spike in the second season and the combined analysis. However, the increase of N level to 90 kg N/fad produced significant decrease in sterile spikeletes number/spike in the both seasons and their combined analysis (Table 2). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Abdel Nour and Fateh (2011), Youssef et al. (2013), Khalid et al. (2014) and Violeta et al. (2015). Interaction effect Significant interaction effects were observed to affect both spikes number/m2, grain number/spike and sterile spikeletes number/spike. Regarding spikes number/m2 (Table 2a) it was significantly decreased by addition of 15.5 P2O5/fad when removal rice straw (rice stubble treatment), but significantly increased when addition of 15.5 P2O5/fad with burning rice straw. A look in the soil analysis showed that experimental soil was moderate in organic matter content (1.03%) and hence, this might play an important
Table 2a Number of spikes/m2 of wheat as affected by rice straw treatments and P level interaction (combined data). Rice straw treatments
N Level effect Rice stubble
In both seasons and their combined analysis, the increase of N level up to 60 kg N/fad was followed by a significant increase in spikes number/m2 and grain number/spike. While, the increase
Burned straw
P level Check
15.5 kg P2O5/fad
A 492.0 a B 386.0 b
B 422.7 a A 417.3 a
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role in availability of micronutrient elements. Addition of P fertilizer under these conditions could reflected an antagonistic effect caused probably by different chelating interaction effects and hence had made P unavailable and caused significant decreased in spikes number/m2. Grain number/spike was affected by the rice straw treatments x N interaction as shown in Table 2b. In the rice straw treatments plots, the increase of N level up to 60 kg N/fad produced a significant increase in grain number/spike where the response equations detected only 58.30 kg N/fad needed to maximize the grain number of spike to 53.29 grain when removal of rice straw compared with 35.22 kg N/fad needed to maximize this number to 61.96 grain when burning rice straw. It is evident from Table 2c that the sterile spikeletes number/spike was significantly decreased due to the increase of N level in rice straw treatments and showed linearity. Grain weight per spike and 1000-grain weight.
et al. (2013) and Violeta et al. (2015). However, the results were not in accordance with those reported by Mekail et al. (2006), Abdul Galil et al. (2008) and Khalid et al. (2014) who reported significant increase in 1000-grain weight due to increase of N level. Interaction effect None of the first order interactions affected significantly the grain weight per spike and 1000-grain weight in the combined analysis (Table 3). This clearly indicated the independence of the main effects of these factors in affecting wheat yield. It was evident that N fertilization level played the major role in affecting yield attributes of wheat. Wheat yields/fad and harvest index. Rice straw treatments effect
Rice straw treatments effect Rice straw treatments had no significant effect on grain weight per spike in both seasons and their combined. However, in the second season and the combined of both seasons, rice straw treatments had significant effect on 1000-grain weight (Table 3). It is evident from Table 3 that the rice straw plowing down treatment recorded heavier 1000-grain weight than burned rice straw treatment. It seems possible that burning rice straw was followed by gaseous losses of N as well as some of elements as P, K, S, Ca, Mg (Ponnamperuma, 1984; Lefroy et al., 1994; Dobermann and Fairhurst, 2002 and Dobermann and Witt, 2000) and hence a possible decrease in soil available nutrients. So, this might have had caused decreased in soil fertility and therefore reflected the decrease in 1000-grain weight. P Level effect The addition of 15.5 P2O5/fad gave significant increase in grain weight per spike and 1000-grain weight though, the grain weight per spike was not significantly increased by this addition in the second season (Table 3). These results are in harmony with those obtained by El-Gizawy (2009), Youssef et al. (2013), Sandaña and Pinochet (2014) and Salim and Abou El-Yazied (2015).
It is evident from Table 4 that, the burning of rice straw recorded lower grain, straw and total yields/fad than the rice straw plowing down treatment. However, the harvest index was increased due to rice straw burning. The decrease of grain yield/fad due rice straw burning was also observed in the number of spikes/ m2 and 1000-grain weight and could account for the decrease observed herein. It seems possible that burning rice straw was followed by losses of NPK and hence a possible decrease in soil fertility (Dobermann and Fairhurst, 2002). P Level effect In both seasons and their combined, the addition of 15.5 P2O5/fad was followed by a significant decrease in grain yield/fad and harvest index as well as the total yield/fad in the combined analysis of both seasons. But, in the second season, this addition was followed by a significant increase in straw yield/fad (Table 4). These results indicate the increase observed in plant height, flag leaf area, grain weight per spike, 1000-grain weight due to P addition was not reflected in grain or total yields/fad and harvest index. These results are not in accordance with those reported by El-Gizawy (2009), Lehoczkyb et al. (2012), Youssef et al. (2013) and Srivatsava et al. (2015) as they reported that, increasing P levels significantly increase of yield and yield attributes of wheat.
N Level effect N Level effect In both seasons and their combined, the increase of N level to 60 kg N/fad produced a significant increase in grain weight per spike, while further increase in N level did not add a further significant increase. However, each increase of N level to 60 or 90 kg N/fad produced at par significant decrease in 1000-grain weight in the first season and the combined of both seasons (Table 3). These results clearly indicate the 60 kg N/fad were enough to increase the grain weight/spike as previously observed in the number of grains/ spike (Table 2). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al. (2010), Youssef
The increase of N level up to 90 kg N/fad gave significant increase in grain and total yields/fad and harvest index. The straw yield/fad was increased due to the first N increment but no further increase was observed due to the second N increment (Table 4). These results are rather expected as almost the yield attributes were increased due to increase in N level. This favorable effect of N may be due its effective role in many biochemical processes in plants (Miller and Donahue, 1990). Similar significant effects were reported by Amal et al. (2005), Weber et al. (2008), Mahrous et al.
Table 2b Number of grains per spike of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (No.)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
B 52.30 a
A 57.15 b
A 58.20 a
52.3 + 6.75 x 1.9 x2
58.3
53.29
Burned straw
B 52.55 a
A 61.75 a
A 57.30 a
52.55 + 16.03 x 6.83 x2
61.96
35.22
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
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Table 2c Number of sterile spikeletes per spike of wheat as affected by rice straw treatments and N level interaction (combined data). Rice straw treatments
N level
ˆ = a + bx c x2 Y
Yˆmax (No.)
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
A 2.70 a
A 2.55 a
B 1.90 a
2.78 0.40 x
Linear
Linear
Burned straw
A 2.60 a
A 2.40 a
B 2.05 a
2.63 0.28 x
Linear
Linear
ˆ max: predicted maximums average Xmax: predicted maximum N level. Y
Table 3 Grain weight per spike and 1000-grain weight of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in two seasons. Main effects and interactions
Grain weight per spike (g)
1000-grain weight (g)
2014/2015
2015/2016
Combined
2014/2015
2015/2016
Combined
Rice straw treatments (S) Rice stubble Burned straw F.test
2.56 2.59 N.S.
2.66 2.56 N.S.
2.61 2.58 N.S.
47.75 47.04 N.S.
47.57 44.72 *
47.66 45.87 **
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
2.48 2.67 **
2.61 2.61 N.S.
2.54 2.64 *
45.83 48.96 **
43.36 48.91 **
44.60 48.93 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
2.31 b 2.67 a 2.75 a **
2.42 b 2.75 a 2.66 a **
2.36 b 2.70 a 2.70 a **
49.86 a 47.58 b 44.74 c **
47.37 a 45.95 b 45.09 b **
48.62 a 46.77 b 44.92 c **
Interactions SxP SxN PxN
N.S. ** **
N.S. N.S. N.S.
N.S. N.S. N.S.
** N.S. **
N.S. * N.S.
N.S. N.S. N.S.
*,** and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
Table 4 Grain, straw, total yields and harvest index of wheat as affected by rice straw treatments, nitrogen and phosphorus fertilization level and their interactions in the two seasons. Main effects and interactions
Grain yield (ton/fad) 2014/ 2015
Straw yield (ton/fad)
Total yield (ton/fad)
Harvest index (%)
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
2014/ 2015
2015/ 2016
Combined
Rice straw treatments (S) Rice stubble 3.17 Burned straw 3.01 F.test *
3.06 3.03 N.S.
3.12 3.02 **
6.48 5.97 **
6.51 6.13 **
6.49 6.05 **
9.65 8.98 **
9.57 9.16 **
9.61 9.07 **
32.85 33.52 N.S.
31.97 33.08 **
32.41 33.30 **
phosphorus level (P) 0 kg P2O5/fad 15.5 kg P2O5/fad F.test
3.17 3.01 **
3.23 2.87 **
3.20 2.94 **
6.23 6.22 N.S.
6.19 6.44 *
6.21 6.33 N.S.
9.40 9.23 N.S.
9.42 9.31 N.S.
9.41 9.27 *
33.72 32.61 **
34.29 30.83 **
34.01 31.72 **
Nitrogen level (N) 30 kg N/fad 60 kg N/fad 90 kg N/fad F.test
2.88 c 3.07 b 3.32 a **
2.68 c 3.01 b 3.45 a **
2.78 c 3.04 b 3.39 a **
6.27 6.25 6.16 N.S.
6.12 b 6.35 ab 6.49 a *
6.19 6.30 6.33 N.S.
9.15 b 9.32 ab 9.48 a *
8.80 c 9.36 b 9.94 a **
8.98 c 9.34 b 9.71 a **
31.48 c 32.94 b 35.02 a **
30.45 c 32.16 b 34.71 a **
30.97 c 32.55 b 34.86 a **
Interactions SxP SxN PxN
N.S. N.S. N.S.
N.S. ** **
N.S. **(4-a) **(4-b)
N.S. ** N.S.
** N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. ** N.S.
** N.S. N.S.
N.S. N.S. N.S.
*,**and N.S. indicate significancy at 0.05 and 0.01 levels and insignificancy of differences, in respective order.
(2010), Lehoczkyb et al. (2012), Youssef et al. (2013), Srivatsava et al. (2015) and Bhatt et al. (2016).
Interaction effect The combined analysis indicated clear significant interaction effect between rice straw treatments and N levels as observed in
grain yield per fad (Table 4a). It is quite evident from Table 4a that the grain yield/fad was not significantly increased unless 90 kg N/fad was added in rice stubble treatment where rice straw was plowed down before sowing. In the burned rice straw plots, each N increase was followed by a significant increase in grain yield/fad but this increase was diminishing. The response equation detected the possibility of maximizing the grain yield/fad to 3.73 ton/fad if
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N level
Yˆ = a + bx c x2
ˆ max (ton/fad) Y
Xmax (kg N/fad)
30 kg N/fad
60 kg N/fad
90 kg N/fad
Rice stubble
B 2.96 a
B 3.02 a
A 3.37 a
2.91 + 0.21 x
Linear
Linear
Burned straw
C 2.60 b
B 3.06 a
A 3.40 a
2.6 + 0.52 x 0.06 x2
3.73
130
Yˆ = a + bx c x2
ˆ max (ton/fad) Y
Xmax (kg N/fad)
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
Table 4b Grain yield (ton/fad) of wheat as affected by P level and N level interaction (combined data). Rice straw treatments
N level 30 kg N/fad
60 kg N/fad
90 kg N/fad
0 kg P2O5/fad
B 2.92 a
B 3.09 a
A 3.58 a
2.87 + 0.33 x
Linear
Linear
15.5 kg P2O5/fad
C 2.64 b
B 2.98 b
A 3.19 b
2.64 + 0.41 x 0.06 x2
3.27
93.46
Yˆmax: predicted maximums average Xmax: predicted maximum N level.
the N level was increased to 130 kg N/fad instead of 3.40 ton/fad obtained due to the addition of 90 kg N/fad. Also, grain yield/fad was affected by the N P interaction as shown in Table 4b. In without P application (0 kg P2O5/fad), no significant increase in grain yield/fad could be detected beyond the addition of 60 kg N/fad. However, in the P fertilized plots with 15.5 P2O5/fad, each increase of N level up to 90 kg N/fad was followed by a significant increase in grain yield/fad. Conclusion The present study was carried out seeking answers for the following questions: Is there any benefit from burning rice straw for the soil fertility and hence yield of the succeeding crop i.e. wheat? Does the addition of mineral N help in speeding up N mineralization and hence the immediate release of NO3 for wheat as well as reduced adverse effects of rice straw burning? Burning of rice straw had significant adverse effect on the grain yield, though this significant effect was observed on some yield attributes as flag leaf area, number of spikes/m2 and 1000-grain weight which is known to have a great contribution to yield variation in wheat. While, the soil incorporation of rice straw had more significant favorable effect on the grain yield and some yield attributes where, rice straw incorporation as a practice of organic manuring, might help in partly solving defects of rice straw burning. On other hand, due to the wide C:N ratio (57:1) of rice straw, a temporary drop of the soil mineral N content, addition of N fertilizer under these conditions could possibly increase gained benefits through enriching soil fertility from a rapid release of available nitrogen. Also, addition of P fertilizer might have had caused improving in soil fertility therefore, reflected on increase in yield and yield attributes of wheat. References A.O.A.C., 2000. Official Methods of Analytical of Association of Official Analysis. Agriculture chemists 17th ed. Washington, N.S.A. Abdel Nour, N.A.R., Fateh, H.S.A., 2011. Influence of sowing date and nitrogen fertilization on yield and its components in some bread wheat genotypes. Egypt. J. Agric. Res. 89 (4), 1413–1433. Abdul Galil, A.A., Basha, H.A., Mowafy, S.A., Mohamed, S.M., 2008. Effect of N level and splitting different levels of P on yield of two wheat cultivars and p use efficiency attributes using sprinkler irrigation system in sandy soil. Minufiya J. Agric. Res. 33 (3), 741–775.
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