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| DOI：10.13522/j.cnki.ggps.20180334 |
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| Optimizing Nitrogen and Phosphorus Fertilization to Improve Sunflower Yield in Hetao Irrigation Districtt |
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LOU Shuai, YANG Shuqing, LIU Ruimin, LIU Deping
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1.Water Conserwancy and Civil Engineering College, Inner Mongolia Agricultural University, Hohehot 010018, China;2. Water Conserwancy and Civil Engineering College, Northeast Agricultural University, Harbin 150030, China
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| Abstract: |
| 【Background】Many farmers in Hetao Irrigation District apply excessive fertilizers as an insurance to ensure yields due to a lack of understanding of what the crops really need. This is not only a waste of fertilizers but could also give rise to water pollution and secondary salinization. Apparently, most research on fertilization has focused on water and nitrogen coupling and overlooked the importance of the combined effects of nitrogen and phosphorus fertilizers.【Objective】This study aims to plug this knowledge gap by systemically studying nitrogen-phosphorus interaction in attempts to reduce non-point source pollution and improve fertilizers use efficiency.【Method】The experiment was conducted in a sunflower field, with four nitrogen fertilizer levels: 0, 120, 240, 360 kg/hm2, and four phosphate fertilizer levels: 0, 52.5, 105, 157.5 kg/hm2. Fertilization used by local farmers, N: 275 kg/hm2 and P: 145 kg/hm2, was taken as the control. Overall, we had 15 treatments. The optimal nitrogen and phosphorus application was estimated by comparing the sunflower yield, plant uptake of nitrogen and phosphorus, and fertilizers use efficiency of all treatments. We also examined the effect of all treatments on soil environment by comparing their associated residual nitrate in soil after harvest.【Result】The interaction of nitrogen and phosphorus fertilizers changed from synergy to antagonism as their applications increased. Crop yield and plant nitrogen uptake change from increase, stagnation to decrease as nitrogen application increased, while the impact of phosphorus application on crop yield was concave - increasing first followed by a decline when phosphorus application exceeded a certain value. It was found that applying 240 kg/hm2 of N and 105 kg/hm2 of P substantially reduced residual nitrogen in soil and increased its uptake by the crop. In particular, compared with the control, it reduced nitrogen and phosphorus fertilizer application by12.7% and 27.6% respectively, while increasing yield by 9.5% and physiological utilization of nitrogen and phosphorus by 8.3 and 40 kg/kg respectively.【Conclusion】Comparative studies revealed that applying 240 kg/hm2 of N and 105 kg/hm2 of P was the most optimal fertilization to reduce N and P application while in the meantime increasing sunflower yield. |
| Key words: nitrogen -phosphorus coupling; fertilizer use efficiency; nitrogen balance; residual nitrogen |
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