الفهرس 
Acknowledgement
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Abstract
Field experiments using four crops (wheat, clover, maize and peanut) through 2009-2012 were designed at Arab El-Awammer Research Station, Agric Res. Center (ARC)., Assiut Governorate, Egypt to evaluate the effect of cultural treatments, S-application and N-fertilizer levels on the yields, yield components, nutrient contents of the tested crops and soil nutrient contents. The experimental design was a split plot design with three replications. In main plots eight cultural treatments were tried four different crop sequences with crop residues completely removed (-CR) or with crop residues incorporated in soil surface layer 0-25 cm (+CR). In the treatments containing crop residues incorporated in the soil, crop residues were chopped and incorporated in soil surface layer (0-25 cm) at the rates of 3.4, 3.6, 1.8 and 2.4 ton /fed from wheat, maize, Egyptian clover (fourth cut) and peanut residues respectively, before cultivating the next crop in crop sequences by 14 to 18 days.
The rates of elemental S (zero and 300 kg powder S/fed seasonally) were in the sub plots. After the first year (seasons 1 and 2), the sub plots were divided in two sub sub plots and the third factor (nitrogen fertilizer rates) was used in the form of ammonium nitrate (33.5% N) at two tested levels (low and high). The low N fertilizer level for the different crops were 60, 15, 120 and 15 kg N/fed while the high N fertilizer levels were 120, 45, 180 and 45 kg N/ fed for wheat, clover, maize and peanut, respectively. Hence, the final experimental design was a split split plot design (8 × 2 × 2) with three replications. Area of each sub sub plot was 3m × 4m = 12 m2 = 1/350 fed.
The results obtained during the course of this study will be demonstrated as follows:-
A) Response of wheat crop to the experimental treatments
B) Response of clover, maize and peanut crops to the experimental treatments.
C) Effect of the experimental treatments on soil properties.
D) Choice of the best crop sequence for different crops productivity and soil fertility.
A) Response of wheat crop to the experimental treatments
Field experiments on wheat (Triticum aestivum L. cv. Sids 1) were conducted during the winter seasons of 2009, 2010, 2011 and 2012, respectively to test the response of wheat crop to cultural practices (different crop sequences with or without crop residues incorporated in soil surface layer) were in main plots. The different four sequences containing wheat crop were:-
Year 2009 2010 2011 2012 legume crop%
Sequence 1 = wheat-maize-wheat-maize - wheat-maize-wheat-maize (0%)
Sequence 2 = wheat-maize-clover-maize - wheat-maize-clover- maize (25%)
Sequence 3 = wheat-maize-clover-peanut- wheat-maize-clover-peanut (50%)
Sequence 4 = wheat-peanut-clover-peanut-wheat-peanut-clover-peanut (75%)
Powder elemental S at the rates of (zero and 300 kg S/fed seasonally) were designed in the sub plots while mineral nitrogen fertilization levels (60 and 120 kg N/fed) were located in the sub sub plots (the third factor in 2010, 2011 and 2012). The experimental design was a split split plot design with 3 replications. Only, the important results of wheat crop obtained after various crop sequences completed in summer season of 2010 will be demonstrated in the following:-
1. Wheat growth parameters (plant fresh weight, dry weight and NP uptake/plant at spiking expulsion), yield and yield components (grain yield, straw yield, biological yield, NP uptake by grain yield, NP uptake by straw yield, NP uptake by biological yield, plant height, averages of spike weight and seed index) were increased significantly due to different cultural treatments as compared with crop sequences 1 (cultivated with continuos cereal crops without crop residues incorporated in soil surface layer).
2. Sequence 4 (75% legume crops + 25% cereal crops) + crop residues resulted in significant increases in wheat grain, straw and biological yields estimated by 78.8%, 55.1% and 63.0% respectively while sequence 3 (50% legume crops + 50% cereal crops) + crop residues resulted in significant increases in wheat grain, straw and biological yields estimated by 69.1%, 49.7% and 56.2% respectively as compared with continues cereal crops sequence 1 (control). Also, the increase recorded in wheat grain yield of sequence 4 + crop residues was significant as compared by sequence 3 + crop residues.
3. Sequence 4 (75% legume crops + 25% cereal crops) + crop residues resulted in significant increases in N and P uptake by wheat biological yield estimated by 109.9% and 99.4% respectively, while sequence 3 (50% legume crops + 50% cereal crops) + crop residues resulted in significant increases in the same parameters estimated by 100.8%, and 83.3% respectively as compared with continues cereal crops sequence 1 (cultivated by wheat and maize without crop residues). Also, the increases recorded in N and P uptake by wheat biological yield of sequence 4 + crop residues were significant as compared by sequence 3 + crop residues.
4. There were significant increases in wheat growth parameter (plant fresh weight, dry weight and NP uptake/plant at spiking expulsion), yield and yield components (grain yield, straw yield, biological yield, NP uptake by grain yield, NP uptake by straw yield, NP uptake by biological) as a result of crop residues incorporated in soil surface layer in crop sequence 1, 2, 3 and 4 as compared with the same treatments without crop residues (crop sequence 1, 2, 3 and 4 respectively), except one cases between sequence 1 & sequence 1 + CR on wheat grain yield (the increase was not significant).
5. Increasing leguminous crop percentage in crop sequences before cultivating wheat crop of 2011 from zero (sequence 1) up to 75% (sequence 4) resulted in additive increases in all estimated parameter of wheat growth, wheat yield and yield components.
6. Sulfur application, at the rate of 300 kg/fed seasonally, induced significant improvement on wheat growth parameter (plant fresh weight, dry weight and NP uptake/plant at spiking expulsion), wheat yield and yield components (grain yield, straw yield, biological yield, NP uptake by grain yield, NP uptake by straw yield, NP uptake by biological yield, plant height and seed index) as compared with the zero S treatment.
7. Nitrogen levels at the rate of 120 kg N/fed, induced significant improvement in all estimated parameter of wheat growth, wheat yield and yield components as compared with 60 kg N/fed. Compared with 60 kg N/fed the increases in grain yield, straw yield and biological yield were 12.2% 13.6% and 13.1% respectively due to the addition of 120 kg N/ fed. Furthermore, compared with 60 kg N/fed the increases in NP uptake by wheat biological yield were 28.9% and 20.1% respectively due to the addition of 120 kg N/ fed.
8. Sulfur application, at the rate of 300 kg/fed seasonally, induced significant improvement in NP uptake by wheat biological yield as compared with the zero S. Also, N levels at the rate of 120 kg N/fed, induced significant improvement in NP uptake by wheat biological yield as compared with 60 kg N/fed. Furthermore, compared with 60 kg N/fed the increases in NP uptake by wheat biological yield were 28.9% and 20.1% respectively due to the higher rate of 120 kg N/ fed.
9. There are two significant interactions of the experimental treatments on N and P uptake, the first between S-application and N-fertilizer levels on N uptake by wheat biological yield and the second significant interaction between cultural treatments and S-application on P uptake by wheat grain yield.
B. Response of clover, maize and peanut crops to the experimental treatments
1. Clover crop
Field experiment was conducted using Egyptian clover (Trifolium alexandrinum cv. Hailaily) during the winter seasons of 2010 and 2012 to test its response to six cultural treatments in main plots, rates of powder elemental S (zero and 300 kg S/fed seasonally) in the sub plots and mineral nitrogen fertilization levels (15 and 45 kg N/fed) in the sub sub plots. The experimental design was a split split plot design with 3 replications. The six cultural treatments were three different crop sequences with crop residues completely removed (-CR) or with crop residues incorporated in soil surface layer 0-25 cm (+CR). The different three sequences (depend on it’s inclusions from legume crops percent) were:-
Year 2009 2010 2011 2012 legume crop%
Sequence 2= wheat-maize-clover-maize-wheat-maize-clover- maize (25%)
Sequence 3= wheat-maize-clover-peanut-wheat-maize-clover-peanut (50%)
Sequence 4= wheat-peanut-clover-peanut-wheat-peanut-clover-peanut (75%)
Only the important results obtained for clover crop in the season 2012 (after crop sequences had been completed) of this study will be demonstrated in the following:-
1. Clover fresh and dry forage yield of different cuts and total cuts (summation of cuts 1, 2, 3 and 4), NP uptake by clover dry forage yield of cuts 2, 3 and total of them were significantly improved due to different cultural treatments. Generally, the obtained values of total cuts of clover fresh and dry forage yield could be descendingly ranked in the following older: All cultural treatments containing crop residues incorporated in soil came in the first rank recording the highest clover yield (fresh and dry forage). Sequence 3 (50% legume crops + 50% cereal crops) was in the fourth rank. Finally sequence 2 came in the last rank (25% legume crops + 75 cereal crops). Sequence 2 + crop residues resulted in 19.72% and 17.18% increases in total fresh and dry forage yield, respectively as compared with the same treatment without CR which came in the last rank.
2. The fresh and dry forage yield of different cuts and total cuts (summation of cuts 1, 2, 3 and 4), NP uptake by dry forage yield of clover cuts 2, 3 and summation of them were significantly increased as a result of crop residues incorporated in soil surface layer in crop sequence 2, 3 and 4 as compared with the same sequences without crop residues.
3. Seasonally sulfur application, at the rate of 300 kg S/fed, induced significant improvement in clover fresh and dry forage yield of different cuts and total cuts (summation of cuts 1, 2, 3 and 4) and significant increases in NP uptake by clover dry forage yield of cuts 2, 3 and the total of them as compared with zero S . Also, S-application resulted in 6.83% and 6.14% increases in fresh and dry forage yield of total cuts.
4. Increasing N–fertilization level from 15 to 45 kg N/fed caused significant increases in fresh and dry forage yields of clover cuts and total cuts (summation of cuts 1, 2, 3 and 4) and NP uptake by clover dry forage yield of cuts 2, 3 and summation of them as compared with 15 kg N/fed. Also, increasing N–fertilization level from 15 to 45 kg N/fed resulted in 6.90% and 5.82% increases in fresh and dry forage yield of total cuts, respectively.
2. Maize crop
Field experiment was conducted on maize (Zea mays L. cv. single hybrid 10) at Arab El-Awammer Research Station, Agric Res. Center (ARC)., Assiut Governorate, Egypt during the summer seasons of 2009, 2010, 2011 and 2012, respectively to evaluate the productivity of sandy calcareous soils as influenced by some cultural practices (different crop sequences with or without crop residues incorporated in soil surface layer). The different three sequences containing maize crop were:-
Year 2009 2010 2011 2012 legume crop%
Sequence 1 = wheat-maize-wheat- maize- wheat-maize- wheat -maize (0%)
Sequence 2 = wheat-maize-clover-maize- wheat-maize-clover- maize (25%)
Sequence 3 = wheat-maize-clover-peanut-wheat-maize-clover-peanut (50%)
Rates of elemental S (zero and 300 kg S/fed seasonally) were in the sub plots and mineral nitrogen fertilization levels (120 and 180 kg N/fed) were in the sub sub plots. Hence, the final experimental design was a split split plot design with three replications; area of each replicate was 3m × 4m = 12 m2 = 1/350 fed.
Results obtained for maize crop after sequences completed in season four of this study will be demonstrated in the following:-
1. Maize yield and yield components (grain yield, straw yield, and biological yield and NP uptake by maize grains) were increased significantly due to different cultural treatments as compared by sequence 1 (continuous cereal crops without crop residues). Such increases were arranged in the following descending; sequence 3 + CR > sequence 2 + CR > sequence 1 + CR > sequence 3> sequence 2 > sequence1.
2. Maize yield and yield components (grain yield, straw yield and biological yield and NP uptake by maize grains) were increased significantly due to crop residues incorporated in soil surface layer in crop sequence 1, 2 and 3 as compared with the same treatments without crop residues.
3. Sulfur application, at the rate of 300 kg/fed seasonally, induced significant improvement on maize yield and yield components (grain yield, straw yield and biological yield and NP uptake by maize grains) as compared with the zero S treatment.
4. Nitrogen levels at the rate of 180 kg N/fed, induced significant improvement in all estimated maize yield parameters (grain yield, straw yield and biological yield and maize grains NP uptake) as compared with 120 kg N/fed.
5. The results of maize crop cultivated in 2010 show many significant interactions. A first significant interaction was between S-application and N-fertilizer levels on maize grain yield, straw yield and biological yield. Second significant interaction was between cultural treatments and sulfur application on NP uptake by maize grains. Third significant interaction was between sulfur application and N-fertilizer levels on NP uptake by maize grains.
3. Peanut crop
Field experiment was conducted on peanut crop (Arachis hypogae L. cv. Giza 6) at Arab El-Awammer Research Station, Agric Res. Center (ARC)., Assiut Governorate, Egypt during the summer season of 2009, 2010, 2011 and 2012, respectively to evaluate the productivity of sandy calcareous soils as influenced by some cultural practices (different crop sequences with or without crop residues incorporated in soil surface layer) in the main plots. The different two sequences containing peanut crop were:-
Year 2009 2010 2011 2012 legume crop%
Sequence 3 = wheat-maize - clover-peanut- wheat-maize-clover -peanut (50%)
Sequence 4 = wheat-peanut-clover-peanut-wheat-peanut-clover-peanut (75%)
Powder elemental S rates (zero and 300 kg S/fed seasonally), were in the sub plots and mineral nitrogen fertilizer levels (15 and 45 kg N/fed) were in the sub sub plot. Hence, the final experimental design was a split split plot design with three replications. Area of each sub sub plot was 3m × 4m = 12 m2 = 1/350 fed. Only, the important peanut crop results obtained in this study will be demonstrated as follows:-
1. Peanut pods yield, straw yield, biological yield, seeds yield, oil yield and NP uptake by peanut seeds were increased significantly due to different cultural treatments as compared by sequence 4 (continuous peanut in summer season).
2. Obtained values of peanut yield and yield components could be descendingly ranked in the following older: Sequence 3 (50% legume crops and 50% cereal crops) + crop residues came in the first rank recording the highest peanut yield and yield components (pods yield, straw yield, biological yield, seeds yield, oil yield and NP uptake by peanut seeds yield) distinguishing significant increases between them and other treatments. Sequence 3 without crop residues came in the second rank recording significant difference between it and the other two treatments which came in the third or last rank sequence 4 (75% legume crops + 25% cereal crops) with crop residues incorporated in surface soil or without. The increases in pods yield, straw yield, biological yield, seeds yield and oil yield of peanut crop in sequences 3 + CR as compared with sequence 4 were 154%, 161%, 158%, 158% and 159%, respectively.
3. Peanut yields (pods yield, straw yield, biological yield, seeds yield, oil yield) and NP uptake by peanut seeds yield were increased significantly due to crop residues incorporated in soil surface layer in crop sequence 3 and 4 as compared with the same sequences without crop residues.
4. Sulfur application, at the rate of 300 kg/fed seasonally, induced significant improvement on peanut yield and yield components parameters (pod yield, straw yield, biological yield, seeds yield, oil yield) and NP uptake by peanut seeds yield as compared with the zero S.
5. Nitrogen fertilizer level at the rate of 45 kg/fed induced significant improvement on peanut yield and yield components and NP uptake by peanut seeds yield as compared with the 15 kg N/fed.
C) Effect of the experimental treatments on soil properties
1. Soil properties after harvesting each crop
Soil properties (soil organic matter, total soil N, soil available P and soil pH) were evaluated after harvesting each crop in each sequence throughout the eight seasons. Important result will be demonstrated on the following:-
1. Soil organic content, soil total N, soil available P and soil pH were improvement significantly due to different cultural treatments. Also, there were significant increases in soil organic matter contents, soil total N and soil available P after crop harvesting as a result of crop residues incorporated in soil surface layer in crop sequences 1, 2, 3 and 4 as compared with the same treatments without crop residues.
2. The significant reductions on soil pH were induced by S-application at 300 kg S/fed seasonally associated with significant increases in soil total N and significant increases in available soil P at crops harvesting.
3. Nitrogen fertilizer levels at the high rate induced significant increases in soil total N and induced significant reduction in soil pH as compared with the low N fertilizer levels.
2. Soil properties after last season (season eight)
2.1. Effect of cultural treatments on soil properties
The important obtained results were:
1. Effect of cultural treatments on soil organic matter content could be arranged in the following descending order; sequence 1 + CR > sequence 2+ CR > sequence 3 + CR > sequence 4+ CR > sequence 1 > sequence 2 > sequence 3 > sequence 4.
2. Effect of cultural treatments on soil total N could be arranged in the following descending order; sequence 1 + CR > sequence 2+ CR > sequence 3 + CR > sequence 4+ CR > sequence 2 > sequence 4 > sequence 3 > sequence 1.
3. Effect of cultural treatments on soil available P could be arranged in the following descending order; sequence 4 + CR > sequence 3+ CR > sequence 1 + CR > sequence 2+ CR > sequence 4 > sequence 3 > sequence 1 > sequence 2.
4. Averages of soil organic matter content, soil total N and available P in plots received CR varied from 0.57%, 130 ppm and 8.5 ppm before cultivating the first season to 1.17%, 563 ppm and 15.46 ppm after eight seasons of cultivation, respectively. On the other hand the average of soil organic matter content, soil total N and available P in the plots without CR varied from 0.57%, 130 ppm and 8.5 ppm before the first season to 0.89%, 459 ppm and 10.44 ppm after eight seasons of cultivation, respectively. Significant decreases in soil pH in the plots received CR as compared with plots received no CR were observed.
2.2. Effect of seasonally powdered S-application on soil properties
The important obtained results were:
1. The averages of soil pH in the plots received S (300 kg S/fed seasonally) varied from 8.35 ppm before the first season to 7.71 after eight seasons of cultivation. On the other hand the average of soil pH in the plots received no S varied from 8.35 ppm before the first season cultivation to 8.01 after eight seasons of cultivation.
2. The averages of soil total N and available P in the plots received powdered S-application varied from 130 ppm and 8.5 ppm before the first season to 529 ppm and 13.71 ppm after eight seasons of cultivation, respectively. On the other hand the averages of soil total N and available P in plots received no powdered sulfur application varied from 130 ppm and 8.5 ppm before the first season to 493 ppm and 12.19 ppm after eight season of planting, respectively.
2.3. Effect of levels of N-fertilizer on soil properties
The important obtained results were:
1. The averages of soil total N and available P in the plots received high N-fertilizer level varied from 130 ppm and 8.5 ppm before the first season to 525 ppm and 13.14 ppm after eight seasons of cultivation, respectively. On the other hand the averages of soil total N and available P in the plots received low N-fertilizer level varied from 130 ppm and 8.5 ppm before the first season cultivation to 497 ppm and 12.75 ppm after eight seasons of planting, respectively.
2. Average of soil pH in plots received high N-fertilizer level varied from 8.35 ppm before the first season to 7.83 after eight seasons of planting. On the other hand the average of soil pH in plots received low N-fertilizer level varied from 8.35 ppm before the first season cultivation to 7.89 after eight seasons of planting.
D) Choice of the best sequence for different crops productivity.
The important obtained results were:
1. Cultivating sandy calcareous soils by cereal crops wheat and maize form season 1 up to season 8 (Sequence 1) resulted in additive decreases in yield and yield components of wheat and maize crops.
2. Cultivating sandy calcareous soils using sequence 2 (25% legume crops + 75% cereal crops) resulted in sustain of yields and yields components of wheat and clover crops.
3. Cultivating sandy calcareous soils using sequence 3 (50% legume crops + 50% cereal crops) resulted in balance and additive increases in yields and yields components of all crops in sequence 3 (wheat, clover, maize and peanut) as compared with other sequences.
4. Cultivating sandy calcareous soil using sequence 4 (75% legume crops + 25% cereal crops) resulted in additive increases in yield and yield components of wheat and clover crop productivity as compared with other sequences. On the other hand this treatment decreases peanut productivity as a result of cultivating the same soil by continues peanut for many seasons.
In conclusion from all previous important results, crop residues applied in legume cereal cropping systems (50% legume crops and 50% cereal crops) resulted in balance of all crops productivity and higher yields, yields components, N and P uptake by seeds of all crops (wheat, clover, maize and peanut) and sustain soil fertility (soil organic matter content, total N, soil available P and soil pH). Powdered S-application at a rate of 300 kg S/fed seasonally and N-fertilizer at the high levels (120, 45, 180 and 45 kg N/fed for wheat, clover, maize and peanut crops, respectively) were also efficient in improving fertility status of the soil.