Effects Of Nitrogen Topdressing At Jointing Stage On Nitrogen Translocation And Grain Yield Of Winter Wheat

Reasonable application of nitrogen fertilizer cannot only improve nitrogenous fertilizer utilization andthe wheat yield, but also reduce the impact on the environment. In order to research the reasonable nitrogenfertilization mode in north of Henan, the effects of nitrogen topdressing at jointing stage on grain yield,economic benefit and nitrogen absorption and utilization of winter wheat were studied during2011-2012.In the field experiments, Zhoumai18and Jimai22were chosen as field experimental materials, which werethe major varieties in Huang-Huai-Hai plain and had higher yield potential. We arranged7nitrogentreatments. One was applying none nitrogen during the whole stage which was expressed as N0, the otherswere nitrogen topdressing at jointing stage based on the basic N fertilizer120kg·hm^-2, and the topdressingrate was0,60,100,140,180and210kg·hm^-2, respectively, which was expressed as N1, N2, N3, N4, N5andN6. The results showed that:1. Nitrogen topdressing at jointing stage played a promoting role on wheat plant height and tillers.Plant height under N3and N4treatment tended to be higher at maturity stage, and the height lowed a littleunder the more nitrogen topdressing. The effective tiller number of the two varieties showed the highestunder N0treatment, and the lowest under N6treatment. Excessive nitrogen topdressing tended to be againstthe plant height and tiller numbers.2. With nitrogen topdressing at jointing stage increasing, the proportion of population dry matteraccumulation and distribution in leaf and ear increased, but in stem and sheath decreased. Appropriateamount of nitrogen topdressing could promote the growth of wheat plant at flowering stage, and it wasbenefit for dry matter accumulation in vegetative organs after anthesis and transportation to grains..Nevertheless, excessive nitrogen topdressing showed the inhibitory affection. At maturity stage, dry matteraccumulation in grains of the two varieties tended to be lower at N6treatment.3. With nitrogen topdressing at jointing stage increasing, nitrogen accumulation in ear reduced and inleaf and stem added during flowering stage. Among all the vegetative organs, nitrogen was mainlyconcentrated in the upper three leaves and stems-sheaths. And nitrogen distribution ratio in leaf decreasedwith the leaf position declined. Nitrogen topdressing had obviously regulatory functions on nitrogentranslocation at maturity stage. With the increase of nitrogen topdressing, nitrogen distribution ratio in vegetative organs dropped, while in reproductive organs added. Higher nitrogen topdressing was one of themost important factors which caused grain protein content and grain yield to decay.4. With nitrogen topdressing at jointing stage increasing, grain yield and economic benefits tended tobe increased and then decreased. The relationship between grain yield and the amounts of nitrogentopdressing could be described as the quadratic equation. According to the fitted equation, we couldcalculate that the grain yield of Zhoumai18and Jimai22was the highest when nitrogen topdressing was144.29kg hm^-2and163.33kg hm^-2, and the grain yield was8.65t·hm^-2and8.16t·hm^-2, respectively. Wecould also calculate that the economic benefit showed the highest when nitrogen topdressing amount was130.26kg·hm^-2for Zhoumai18and130.60kg·hm^-2for Jimai22. With these theoretical nitrogentopdressing, the grain yield of Zhoumai18was8.63t·hm^-2, and Jimai22was8.13t·hm^-2, and meanwhilethe economic benefits were11,787Yuan·hm^-2and10,657Yuan·hm^-2.5. From the point of fertilizer benefit, Zhoumai18and Jimai22achieved the maximum under N4andN5treatment, respectively. With the amount of nitrogen topdressing increasing, TNAA （total nitrogenaccumulation amount） in plant increased slowly and sometimes decreased, and meanwhile NHI （nitrogenharvest index） decreased significantly.81%⁸9%of nitrogen accumulation in grain was the remobilizationfrom the vegetative organs after anthesis, and different nitrogen topdressing treatments were not consistent.NHI and NUE （nitrogen utilization efficiency） had a positive relationship with NPEP （nitrogen partialfactor productivity）, while TNAA had a negative correlation with NPEP. NRE （nitrogen recovery efficiency）showed the highest under the N3treatment which topdressing amount was100kg hm^-2.Taken the above together,120kg hm^-2nitrogen as base N fertilizer with140kg hm^-2nitrogen astopdressing at jointing stage was the applicable nitrogen applying mode in northern Henan.