Research On Nitrogen Fertilizer Effect On Annual Relay Intercropping System Of Wheat/Maize/Soybean

"wheat/maize/soybean" annual relay interplanting system as the research object in this study, field experiment was carried out in 2011 and 2012 to investigate the effect of nitrogen fertilizer (for wheat 0,60,120,180,240 kg-hm-2, marked as WN1、WN2、WN3. 、WN5; for maize 0,97.5,195,292.5,390 kg·hm-2, marked as MN1、MN2、MN3、 、MN5; for soybean as SN1、SN2、SN3、SN4、SN5; for system as N、N2、N3、 N4、 N5) according to the current situation, that production of nitrogen fertilizer increased low utilization rate of nitrogen fertilizer, in order to guide local agricultural production, and build a reasonable application of nitrogen fertilization to reducing environmental pollution and improve the utilization ratio of fertilizers. The result showed that:(1)Nitrogen fertilizer was beneficial to tillering and dry matter accumulation input grain amount, it was increased firstly and then decreased as nitrogen increased, tiller number and input grain amount were biggest in WN4, respectively 2.3 and 8389 kg·hm-2. The contributed input grain amount of WN4 was 91.6%, no significant difference with WN3. Wheat and maize plant height increased with the increase of N application rate within a certain range, nitrogen fertilizer more than WN3 (120 kg·hm-2), MN3 (195 kg-hm-2) there was no significant difference. Dry matter accumulation amount, dry matter accumulation rate and maize leaf area index, leaf area accumulation rate, photosynthetic potential, net assimilation rate of wheat and maize were increased with the increase of nitrogen application, more than WN3 or MN3 increase was not significant. Dry matter production has obvious edge line advantage, edge rows wheat variation coefficient is greater than innner one, by the degree of disturbance (intraspecific and interspecific) is the largest, greater sensitivity to the environment than inner rows, and nitrogen application more multilateral line advantages more apparent. Dual function of soil fertility and the intensity of competition makes soybeans from SN1～SN5 plant height, dry matter accumulation and accumulation rate decreased first then increased and then decreased.(2)N application significantly increased the yield of wheat and maize, there was no significant difference between WN3～WN5, none nitrogen treatment less then nitrogen treatment increase 21.4%～111.9%, to WN3 maximum of wheat was 8317 kg-hm-2, nitrogen treatment’s yield was 2.83-3.82 times then none nitrogen treatment, the yield of MN3 was 6619 kg·hm-2 was maximum. Edge rows of wheat yield significantly greater than the inner rows, with the increase of N application, the difference between edge and inner rows also will increase, edge rows yield increased by 41.5～83.1% than the inner rows. Proper soil fertility in favour of increased yield of soybean, from SN1～SN5, the yield of soybean decreased first and then increased then decreased, the maximum treatment was SN4, for 1603 kg·hm-2(3)N-fertilizer was beneficial to increased nitrogen content and accumulation of wheat and maize organs, nitrogen content and total nitrogen accumulation had no significant change when Nitrogen fertilization more then WN4(180 kg·hm-2)and MN4(292.5 kg·hm-2); nutrient absorption and accumulation also showed edge line advantage,soybean nitrogen content and accumulation reduced rise first and then decreased, with SN4 biggest, and there was no significant difference between SN4 and SN5.(4)Nitrogen decreased P2O5 content in different organs of maize and wheat, while significantly increased the P2O5 accumulation, P2O5 content of grain, WNi increased by 8.8～18.8% than nitrogen treatment, the MN1 was 3.7%～26.5% higher than nitrogen treatment, the accumulation of P2O5 W (M) N3-W (M)N5 there was no significant difference between; nutrient absorption and accumulation also showed edge line advantage, proper soil residual nitrogen is beneficial to the increase of soybean grain P2O5 content and accumulation, has increased from SN1 to SN5, there was no significant difference between SN5 and SN4.(5)Nitrogen application increased the grain K2O content and the accumulation of total aboveground K2O, K2O content of WN5 was 15.5%-38.9% higher than the other, the K2O ccumulation of WN5 was 6.5～118.1% higher than the other, there was no significant difference between WN4 and WN5; Nutrient absorption and accumulation also showed edge line advantage. Nitrogen reduces the K2O content of maize stalks, leaves and grains, but increased the maize K2O accumulation; stalks of MN1 K2O content was 20.4%-57.5% higher than nitrogen treatment and K2O content of leaf MN1 9.6～29.4% higher than nitrogen treatment and MN1 grain of K2O content 9.3%～34.6% higher than the nitrogen treatment; When nitrogen application was greater than 292.5 kg·hm-2 does not significantly increase the accumulation of K2O. nitrogen in the soil after wheat harvest made soybean K2O content reduced, K2O content with SN1 highes in SN1～SN5, among treatments K2O content was decreased first and then increased, same with K2O accumulation of soybean, there was no significant difference between SN1, SN4 and SN5, that provided if appropriate proper phosphate and potash, even nitrogen deficiency soybean could grow well.(6)Nitrogen application significantly increased wheat 0-40 cm soil inorganic nitrogen content, nitrogen application treatment 0-20 cm soil inorganic nitrogen content was 6.8～27.4% more than none nitrogen, nitrogen application treatment of 20～40 cm soil inorganic nitrogen content than none nitrogen increased 23.2-82.9%; Maize 0-40 cm soil inorganic nitrogen content in MN3 was minimum, MN1 and MN2, MN4 and MN5 was 1.6-2.5 times than MN3, low nitrogen treatment and high nitrogen were increased by 0-40 cm soil inorganic nitrogen content; maize belt soil from surface to underground 1 m, inorganic nitrogen content gradually reduce, excess precipitation would result in higher inorganic nitrogen content in deep soil layer and enrichment layer (60～80 cm) arised.0～40 cm soil inorganic nitrogen content from SN1 to SN5 gradually increase; if nitrogen application more than 180 kg·hm-2 of "Wheat-soybean" crop rotation planting, inorganic nitrogen content in 20～40 cm> 0～20 cm, there was a risk of infiltration to drench.(7)N4 was the largest treatment of system annual earning, it was 13936yuan·hm-2, output-input was 2.12, and 160.5% higher then none nitrogen treatment output, but there was no significant differences between N4 and N5.(8)Without considering precipitation, atmospheric precipitation and leaching, nitrogen input and absorption was level off in the N4(nitrogen apparent balance of -1 kg-hm-2), nitrogen fertilizer below the N4 (382.5 kg·hm-2), nitrogen input was not enough, more than N4 interchange was overmuch, caused waste of resources and environmental pollution; system in high yield (N3～N5) of phosphorus fertilizer significantly less, N3, N4, N5 phosphorus apparent balance was 14.9～38.0 kg·hm-2; nitrogen treatment (N2～Ns) of potash apparent balance is 12.4～89.8 kghm-2, was also insufficient.(9)Annual system of nitrogen apparent utilization ratio in N4 maximum, the largest was 56.2%; the system output N3, N4 and N5 there was no significant differences among. 100kg grain need fertilizer (N, P2O5, K2O) were lowest in N3 among N3～Ns, system utilization rate of nitrogen fertilizer on nitrogen application at N3～N4 interchange (255～382.5 kg·hm-2) was more reasonable.(10) Combining with the production analysis and nutrient accumulation, the suitability of nitrogen rate are 120～180 kg·hm-2 for wheat,195～292.5 kg-hm-2 for maize,255～382.5 kg·hm-2 for the annual system with proper nitrogen top application or no application for soybean according to the growth. Phosphorus and potassium were apparent lack in the high yield (N3-N5) (system P2O5 fertilization was 120 kg·hm-2; K2O system fertilization was 150 kg·hm-2), should make appropriate complement; besides "wheat/maize/soybean relay interplanting system, maize as the main value crops, followed by wheat, then was soybeans, and soybean had the highest output-input ratio (the average was 3.5), each treatment of wheat all showed nitrogenous fertilizer inputs<uptake, and maize in N3 treatment showed nitrogen inputs>uptake, it was recommended that on the premise of ensure maize yield, the system of total nitrogen fertilizer inputs should shift to wheat and soyabeans, namely increasing nitrogen application rate of wheat, soybean from previous none nitrogen instead of just the right amount of nitrogen.