Six seasons of experiments in Machakos, Kenya, revealed that above about 150 mm of rainfall, maize yields per row in alley cropped “replacement” agroforestry (AF) plots, of Cassia siamea Lam. and maize ( Zea ma...Six seasons of experiments in Machakos, Kenya, revealed that above about 150 mm of rainfall, maize yields per row in alley cropped “replacement” agroforestry (AF) plots, of Cassia siamea Lam. and maize ( Zea mays, cv. Katumani Composite B), may be expected to exceed those in the control (sole maize) plots. Such yields were insufficient to compensate for the area “lost” to the hedgerows. Below about 150 mm the control plots may be expected to perform better. This result was due to competition for water. Greater association of the fine roots of Cassia and maize was observed in the middle of the alleys than near the hedgerows. Photosynthetic consequences of shading were insignificant relative to other factors. In the alleys, reductions of soil temperature due to shade in the western and eastern maize rows were higher than in the middle row. Soil moisture extraction was higher in the AF than in the control plots. In the AF plots, moisture extraction was greater under the central maize rows than under those nearest the Cassia. Yield patterns followed such soil temperature and soil moisture patterns. Maize transpiration and photosynthetic rates were significantly higher in the control than in the AF plots during a below average rainy season but not during above average rainy seasons. It is concluded that alley cropping under semi arid conditions should be approached differently from the system worked on. It must at least provide strong physical protection of crops and/or soils and have a strong economic incentive to be of interest to the farmers.展开更多
A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven ...A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control （CK） and six different combinations of phosphorus （P）, potassium （K）, nitrogen （N）, straw （S） and animal manure （M）. The balanced fertilization treatments had significantly （P〈0.05） higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate （NPK） and 1/3 N from farmyard manure （NPKM） had a higher average yield than the other treatments. The average yields （over the 23 years） in the treatments of NPK, and urea, calcium superphosphate （NP） did not differ significantly （P〉0.05） but were higher than that in the treatment with urea and potassium sulfate （NK; P〈0.05）. The results also show that the highest increases in SOC （P〈0.05） occurred in NPKM with a potential increase of 1.2 t C/（hm2.a）. The increase in SOC was only 0.31, 0.30 and 0.12 t C/（hm2.a） for NPKS （9/10 N from NPK and 1/10 N from straw）, NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.展开更多
Alley cropping of Cassia siamea and maize was studied in semi arid Kenya for soil fertility improvement. Katumani composite maize was planted except in the short rains of 1988 (SR88) when a hybrid variety was sow...Alley cropping of Cassia siamea and maize was studied in semi arid Kenya for soil fertility improvement. Katumani composite maize was planted except in the short rains of 1988 (SR88) when a hybrid variety was sown. Therefore the grain yield per row increased differently in the alley cropped maize (CM). Sole maize (SM) and CM yields were higher in SR88 than in the long rains of 1988 (LR88) by 62% and 38%, while yields from the same treatments in LR89 were only 21% and 45% of those in SR88 These differences in relative maize yields are attributed to differences between the two maize varieties in competition under nutrient stress conditions.展开更多
文摘Six seasons of experiments in Machakos, Kenya, revealed that above about 150 mm of rainfall, maize yields per row in alley cropped “replacement” agroforestry (AF) plots, of Cassia siamea Lam. and maize ( Zea mays, cv. Katumani Composite B), may be expected to exceed those in the control (sole maize) plots. Such yields were insufficient to compensate for the area “lost” to the hedgerows. Below about 150 mm the control plots may be expected to perform better. This result was due to competition for water. Greater association of the fine roots of Cassia and maize was observed in the middle of the alleys than near the hedgerows. Photosynthetic consequences of shading were insignificant relative to other factors. In the alleys, reductions of soil temperature due to shade in the western and eastern maize rows were higher than in the middle row. Soil moisture extraction was higher in the AF than in the control plots. In the AF plots, moisture extraction was greater under the central maize rows than under those nearest the Cassia. Yield patterns followed such soil temperature and soil moisture patterns. Maize transpiration and photosynthetic rates were significantly higher in the control than in the AF plots during a below average rainy season but not during above average rainy seasons. It is concluded that alley cropping under semi arid conditions should be approached differently from the system worked on. It must at least provide strong physical protection of crops and/or soils and have a strong economic incentive to be of interest to the farmers.
基金funded by the National Basic Research Program of China(2014CB954200)the National Natural Science Foundation of China(41425007,41005001)the National Gray Desert Soil Fertility and Fertilizer Efficiency Monitoring Station of China
文摘A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control （CK） and six different combinations of phosphorus （P）, potassium （K）, nitrogen （N）, straw （S） and animal manure （M）. The balanced fertilization treatments had significantly （P〈0.05） higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate （NPK） and 1/3 N from farmyard manure （NPKM） had a higher average yield than the other treatments. The average yields （over the 23 years） in the treatments of NPK, and urea, calcium superphosphate （NP） did not differ significantly （P〉0.05） but were higher than that in the treatment with urea and potassium sulfate （NK; P〈0.05）. The results also show that the highest increases in SOC （P〈0.05） occurred in NPKM with a potential increase of 1.2 t C/（hm2.a）. The increase in SOC was only 0.31, 0.30 and 0.12 t C/（hm2.a） for NPKS （9/10 N from NPK and 1/10 N from straw）, NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.
文摘Alley cropping of Cassia siamea and maize was studied in semi arid Kenya for soil fertility improvement. Katumani composite maize was planted except in the short rains of 1988 (SR88) when a hybrid variety was sown. Therefore the grain yield per row increased differently in the alley cropped maize (CM). Sole maize (SM) and CM yields were higher in SR88 than in the long rains of 1988 (LR88) by 62% and 38%, while yields from the same treatments in LR89 were only 21% and 45% of those in SR88 These differences in relative maize yields are attributed to differences between the two maize varieties in competition under nutrient stress conditions.
