Effect Of Nitrification Of Ammonia From Urea Hydrolysis On Soil Nitrogen Supply And Wheat Root Growth

Urea has a high nitrogen content, nature is relatively stable, long-termfertilization on soil without damage, is the application of agricultural production thelargest number of nitrogen species. But for a long time, there has been the problem ofnitrogen fertilizer utilization is low, serious loss, not only caused a lot of nitrogen lossenergy waste and low economic efficiency of agriculture, but also seriousenvironmental pollution. In order to explore the urea hydrolysis characteristics in thedrought area of west Henan, provide a theoretical basis for the rational application ofurea, reduce losses and improve the utilization of urea. In this study, field trials wereconducted in carbonate drab soil of Luoyang in2011²012. The experiment set thefertilization period （before planting20d,10d,0d, seeding on the same day） andnitrogen species （control, urea, urea+ammonium sulfate, sodium nitrate, ammoniumchloride）. Hydrolysis of urea ammonium nitrate characteristics and laws, soil nitrogensupply, soil enzyme activity, wheat growth and the physiological metabolism in soil asaffected by N fertilizer forms during wheat growth were studied under differentfertilizing period. The main result was as follows:1. Under dry land conditions, Urea hydrolytic and nitrification were closelyrelated to fertilizing time. In the case of early of20days or10days of sowing, soilNO₃^--N to spike after13days. Nitrifications of ammonia and urea type nitrogenfertilizers were completed in13days. Under regular fertilize, soil NO₃^--N to spikeafter23days. Different forms of nitrogen in the soil after fertilization contentincreased significantly, high nitrate levels last longer than ammonium nitrogen. Afterthe application of ammonium nitrogen fertilizer13²3days, Soil ammonium nitrogencontent can be reduced to control, but nitrate content has been below the nitratenitrogen treatment. 2. Consolidated nitrification ration, nitrification rate, net mineralization andnet nitrification. The studies also show that adoption of substrate induction method, or addition of a small amount of ammonium N （20%ammonium sulfate Nof the total N） to urea （80%of the total N）, as a substrate for nitrifiers, canaccelerate urea nitrification. With the application of mixed nitrogen fertilizer, thenet mineralization and net nitrification were elevated by21.9%,35.8%.3. N application significantly improved soil nitrate and ammonium content.Ammonium nitrogen content reached its peak in the Jointing stage and Filling stage,showing the M-type changes; and soil nitrate changes more smoothly, Its contentalong with the advancement of wheat growth period at a low level. The soil nitrogensupply changed differently under each N fertilizer form. Mixed nitrogen can improvethe0⁵cm and15²0cm rhizosphere ammonium nitrogen and nitrate content. Amidenitrogen can significantly increased5¹0cm and10¹5cm rhizosphere ammoniumnitrogen and0⁵cm non-rhizosphere ammonium and5¹0cm rhizosphere or non-rhizosphere nitrate content. And ammonium nitrogen could effectively improve15²0cm rhizosphere ammonium and nitrate nitrogen content.4. After nitrogen fertilizer, both rhizosphere and non-rhizosphere soil pH valuealthough have some change, the biggest difference between the groups of0.3units, butthere was no significant difference between nitrogen forms treatment. Using nitratenitrogen, rhizosphere pH has a rising phenomenon, while using ammonium nitrogenhave decline phenomenon. With the absorption of wheat of ammonium or nitrate, thesoil pH has been raised or lowered, but not have a direct impact on soil properties.5. N application significantly improved soil enzyme activities. With theapplication of N fertilizer, the urease, protease, invertase, dehydrogenase andcatalase activities were elevated by60.3%,36.0%,36.7%,100%, and33.8%onaverage, respectively. On average, the coefficient variation of the soil enzymeactivities under different N forms followed the order of urease>dehydrogenase>protease>invertase>catalase. The soil enzyme activities changed differently undereach N fertilizer form. The amide nitrogen fertilizer will can improve the soilprotease activity and0²0cm soil urease activity; ammonium nitrogen fertilizerwill help improve the soil dehydrogenase activity and0²0cm soil catalaseactivity and20⁴0cm soil invertase; nitrate and mixed nitrogen increased20⁴0cm soil urease and catalase activity,0²0cm soil invertase activity. 6. Compared to nitrate and ammonium nitrogen, nitrate of wheat leaf dry weight32%higher compared ammonium nitrogen, total biomass of39%, average daily gainof34.5%; The root dry weight, root cap ratio, root vigor were stimulated by NO₃^--N,respectively, and NR activity, soluble sugar content were the highest in NO₃^--Ntreatment. Nitrogen uptake, absorption efficiency is higher than other treatments79.5%and38.5%, respectively, and assigned to the root in the proportion of4.4%.7. Under dry land conditions, effects of nitrogen fertilizer on wheat yield andyield related traits （spike number, seed number per spike, seed weight） showeddifferent effects. Nitrate nitrogen can increase the number of spike and seed weight perspike. Comprehensive the yield of the three fertilization period mean value point ofview, the production order: SN>AS+U>AC>U>CK. As a final result, the wheat yieldwith application of nitrate N was69.3%higher than the control,13.2%higher than theammonium N,22.9%higher than CO（NH2）2-N and9.1%higher than mixed nitrogen.The wheat yield with application of mixed N was12.7%higher than amide nitrogen.