Study on the suitable application rate and method of urea with short controlled-release period in winter wheat

【Objectives】The application effect of controlled-release urea is usually affected by temperature,soil moisture and other environmental factors,so the reported effect was varied. To provide theoretical and technical supports for selecting the appropriate nitrogen fertilizers and application methods,two comparison experiments between the controlled-release urea and common urea application on winter wheat were performed.【Methods】 A wheat cultivar,Xinmai 26 was used as the experimental crop,and two field experiments were designed with a randomized block. Grain yield,quality traits,nitrogen use efficiency and economic benefit of winter wheat between controlled-release urea and common urea were systematically studied. In the 1st experiment, the controlled-release urea was basal applied in one time, and 60% of commercial urea was basal applied and 40% top dressed at reviving stage, all the two kinds of urea were applied in the five levels: 0(CK1),120,160,200 and 240 kg/hm2,respectively. In the second experiment, using no N fertilizer as control(CK2),200 kg/hm2 of N was applied, and controlled-release urea and commercial urea were all applied in ratio of top-dressed 40%.【Results】 1)Compared to CK1,grain yield of winter wheat was significantly increased with the increase of nitrogen application rates of both controlled-release urea and common urea,and the treatment with common urea split application reached the highest grain yield as much as N 240 kg/hm2. Compared with controlled-release urea one-time application at the same nitrogen rate,the treatment with common urea split application could significantly increase grain yield of winter wheat but not exhibit significant difference at the N 160 kg/hm2 nitrogen rate. However,compared with topdressing common urea at reviving stage,topdressing controlled-release urea could significantly increase grain yield of winter wheat by 15.8%. 2)Under the same nitrogen rate,compared with controlled-release urea one-time application as base fertilization,common urea split application could increase grain bulk density,grain protein content,grain moisture content,wet gluten content of winter wheat,and grain bulk density at nitrogen application rate with N 160 kg/hm2 and N 200 kg/hm2 exhibited significant increases. However,topdressing controlled-release urea at reviving stage could significantly increase grain bulk density,wet gluten content and grain protein content of winter wheat compared with topdressing common urea. 3)Nitrogen use efficiency such as nitrogen fertilizer agronomic efficiency and nitrogen partial productivity was decreased with the increase of nitrogen application rate for both common urea and controlled-release urea,and nitrogen use efficiency in the treatment with common urea split application was significantly higher than that in the treatment with controlled-release urea one-time application at the same nitrogen rate. Compared with common urea split application,controlled-release urea one-time application as base fertilization reduced labor cost of nitrogen topdressing at the jointing stage of winter wheat,but the grain yield decreased and the increase in input cost eventually resulted in lower economic benefit in the treatment with controlled-release urea one-time application. However,the results of 2nd experiment showed that,compared with topdressing common urea at reviving stage of winter wheat,topdressing controlled-release urea at this stage could significantly increase nitrogen use efficiency including nitrogen fertilizer agronomic efficiency,nitrogen partial productivity and nitrogen N recovery efficiency,and economic benefit. 【Conclusions】The rate of recommended nitrogen is 200 kg/hm2 in this region. Based on a consideration of labor shortage of farmers,controlled release urea is suitable for one-time base application,and when farmer labors are abundant,common urea is suitable for base and topdressing fertilizer,or controlled-release urea suitable for topdressing fertilizer at reviving stage of winter wheat. Therefore,appropriate urea types and application methods as nitrogen fertilizer could be chosen to increase farmers income depending on the actual situation under the background of limited labor in rural area as well as increase in labor force cost and decrease in benefits of growing grain crop at present.