Study On The Coupling Effects Of Controlled Release Urea And Water On Nitrogen And Water Utilization, Yield And Quality Of Maize

To find out the measurements of increasing fertilizer and water use efficiency by the combination of fertilization and irrigation. Using field experiments and pot experiments, this study analysed the effects of water and nitrogen on N utilization, yield and quality, root distribution and activity, and root and shoot relationship of maize. The results are useful to improve nitrogen and water use efficiency and supply a principle and technology of high yield and good quality for maize cultivation. The principal results were as follows:1. Effects on N utilizationThe N uptake of CU was significantly higher than that of normal urea treatment. The N uptake was increased with filling irrigation at the same nitrogen level. The grain nitrogen assimilation after anthesis with 75 kgN/ha treatment of NU was lower than that of N0 treatment, but that with 75 kgN/ha treatment of CU was higher than that of N0 treatment. N translocation did not increase nitrogen transported from accumulation of vegetative organs to grains with filling water, and at harvest, a higher percentage of nitrogen remained in vegetative organs. The amount of nitrogen transported from accumulation pre-anthesis of vegetative organs with 150 kgN/ha treatment of NU was lower than that of 75 kgN/ha treatment. Increasing application rates of NU could decrease nitrogen transported from vegetative organs to grains, while increasing application rates of CU was on the contrary. Results showed that CU could increase the nitrogen uptake to grain. There was little effect on ammonia nitrogen content of soil water content, nitrogen type or amount.The nitrogen content of treatments applied with nitrogen was higher than that of treatments without nitrogen applied. The CU could release nitrogen slowly, increase plant absorbtion and thus reduced soil nitrogen content. Soil nitrate nitrogen content increased with nitrogen apllied. Soil nitrate nitrogen content of irrigated was higher than that of no irrigation. This showed irrigation increased soil nitrate nitrogen content, which was because irrigation enhanced leaching of nitrate nitrogen and reduced the efficiency of fertilizer, while CU could reduced leaching of nitrate nitrogen because of slow nitrogen release.2. Effects on the WPEIncreasing nitrogen application could enhance WPE of total water. WPE of total water was decreased with filling. WPE of CU was significantly higher than that of normal urea treatments. This research also showed that increasing nitrogen application rates can enhance WPE of irrigation, and that of CU was higher than that of NU treatment, which was significantly with 75 kgN/ha.3. Effects on photosynthesis of maizeThe CU could maintain higher net photosynthesis rate and chlorophyll content by releasing slowly and supporting enough nitrogen at the late stage. Net photosynthesis rate and chlorophyll content increased when nitrogen applied amount increased. The net photosynthesis rate and chlorophyll content of irrigation treatments were higher than those of no irrigation treatments. CU had higher net photosynthesis rate and chlorophyll content than normal urea treatments at different stages, which was more obvious at later stages. Also grain filling water could significantly increase the effects. The CU had higher SOD and POD activity, soluble protein content and physiological activity, but lower MDA content. This effect was significantly enhanced by grain filling irrigation. Results showed that CU and irrigation could increase anti-oxidative capability and extend function stage thus increased yield.4. Effects on yield of maizeIncreasing nitrogen application rates can enhance grain yield of maize, significantly. Compared with the normal urea, shoot dry weight and leaf area index of maize applied with CU were lower than those applied with NU before anthesis, but the situation was just contrary after anthesis. And as a result, the grain yield and biomass applied with CU were higher than those applied with NU. The CU can enhance grain yield, and suitable soil moisture is beneficial to improve the superiority of controlled release urea.5. Effects on grain quality of maizeThe CU can increase grain protein content and yield, significantly because of the CU can enhance total N uptake of maize, grain nitrogen assimilation after anthesis. Grain protein content was decreased, the yield was increased with filling water, and the grain protein content and yield of CU were higher than that of NU treatment. Nitrogen fertilizer type and application amount had significant effects on fat content and starch content of grain. Fat content and starch content of maize with CU were higher than those with normal urea. Fat content and starch content of grain were increased when nitrogen applied amount increased. Grain filling water could increase fat content and starch content of maize grain.6. Effects on root and shoot relationship and yield of maizeEffects of first control and then maintain of CU can explain the coordinate growth of root and shoot. The root amount and activity of CU were higher than that of NU treatment, and CU coordinates the relationship between root and shoot well, that could increase grain of maize. The enhancement of coupling of controlled release urea and water was by icreasement of root amount and activity and coordinate growth of root and shoot. 7. Better water-nitrogen mode for maizeApplying CU with amount of 75kg N/ha could increase yield by 9.6% and increased yield by 13.8% after irrigation with the amount of grain filling water of 85mm. This had high water and fertilizer using effects. While the best nitrogen content still need to be researched with considering all the factors of nitrogen use, yield and quality.