控释氮肥与尿素混施对连作春玉米产量、氮素吸收和氮素平衡的影响

【目的】控释氮肥与普通尿素进行掺混施用是行之有效的一次性施肥替代技术。明确控释氮肥与尿素掺混施用对春玉米产量、氮素吸收利用以及土壤-作物系统氮素平衡的影响,为春玉米氮素养分的科学管理技术提供参考。【方法】2010和2011年在吉林省中部玉米主产区连续2年设置大田定点试验,施肥处理包括:不施氮(N0)、100%尿素(CRN0%)、15%控释氮肥+85%尿素(CRN15%)、30%控释氮肥+70%尿素(CRN30%)和45%控释氮肥+55%尿素(CRN45%),研究控释氮肥与尿素掺混施用对春玉米连作条件下籽粒产量、氮素吸收与利用、土壤无机氮累积与矿化以及系统氮素平衡的影响,确定适宜的控释氮肥掺混比例。【结果】与尿素一次性全施相比,控释氮肥与尿素掺混施用显著提高了春玉米地上部干重和产量,不同掺混比例之间差异不显著。两季平均结果显示,CRN30%处理玉米产量达最高(9.39 t·hm~(-2)),较CRN0%处理增产9.0%(0.77 t·hm~(-2)))。施肥是土壤-作物系统主要的氮素输入方式,占总输入量的63.5%,播前土壤无机氮和氮素矿化分别占19.2%和17.3%。2010和2011年玉米生育期内土壤氮素的表观净矿化量分别为34.4和66.1 kg·hm~(-2)),两季之间越冬期各施肥处理土壤氮素矿化量为15.2—26.4 kg·hm~(-2)),处理间差异不显著。系统的氮素输出以植株吸收带走氮素为主要方式,平均占总输出的80.7%(68.1%—99.5%)。随控释氮肥掺混比例的增加,植株氮素吸收量和土壤无机氮残留量均呈持续上升趋势,分别在CRN30%和CRN45%处理达最高,为234.2和108.1 kg·hm~(-2),较CRN0%处理分别增加18.0%和45.1%。但是,氮素表观损失随控释比例增加而大幅降低,最终导致氮素表观盈余也呈下降趋势,CRN30%处理降至最低的114.4 kg·hm~(-2)),较CRN0%处理减少38.4%。控释氮肥与尿素掺混处理表层土壤(0—30 cm)的无机氮含量明显高于CRN0%处理,而深层土壤(30—90 cm)则较低,表明其氮素下移趋势较小。两季平均结果表明,氮肥的表观利用率由CRN0%处理的50.1%显著提高至CRN30%处理的69.4%,表观残留率在控释氮肥掺混施用后均显著提高,而表观损失率从CRN0%处理的37.3%显著下降至CRN45%处理的6.0%。【结论】控释氮肥与尿素掺混施用可促进春玉米获得高产,增加植株氮素吸收,而且维持了较高的土壤氮素水平并减少损失,从而提高氮肥利用率。当前生产条件下,东北春玉米施氮185 kg N·hm~(-2))条件下适宜的控释氮肥掺混比例在30%左右。

Effects of Mixed Application of Controlled-Release N Fertilizer and Common Urea on Grain Yield,N Uptake and Soil N Balance in Continuous Spring Maize Production

【Objective】The mixed application of CRN and common urea was considered as a good alternative technique for single basal fertilizer application. This study aimed to evaluate the effects of mixed application of CRN and urea on grain yield, N uptake, N balance in a soil-crop system, and to provide reference to scientific N management techniques for spring maize.【Method】A two-year fixed plot experiment was conducted in the major maize production area in the central Jilin province from 2010 to 2011, including five fertilization treatments, including Treatment I (No N fertilizer, N0), Treatment II (100% urea, CRN0%), Treatment III (15% CRN+85% urea, CRN15%), Treatment IV (30% CRN+70% urea, CRN30%), and Treatment V (45% CRN+55% urea, CRN45%). In this study, grain yield, N uptake, N efficiency of spring maize, soil inorganic N accumulation and mineralization, and N balance in soil-crop system were investigated, and the appropriate mixed ratio of CRN was determined by considering comprehensive performances.【Result】The results showed that mixed application of CRN and urea increased significantly aboveground dry matter and grain yield of spring maize, compared with single basal application of urea, while no differences were found between the various mixed ratios. On an average of two growing seasons, the highest grain yield of 9.39 t·hm^-2 was obtained in the CRN30% treatment, which was 9.0% (0.77 t·hm^-2) higher than that in the CRN0% treatment. Application of N fertilizer was a major way of N input in soil-crop system, which accounted for 63.5% of the total N input, while the contributions of soil inorganic N prior to sowing and N mineralization were 19.2% and 17.3%, respectively. The net N mineralization during maize growing season was 34.4 kg·hm^-2 in 2010 and 66.1 kg·hm^-2 in 2011, while that was in the range of 15.2-26.4 kg·hm^-2 among treatments during the overwintering stage between two growing seasons. Cropped N uptake by maize plants was a major way of N output and its contribution ranged from 68.1% to 99.5% with an average of 80.7%. With increasing mixed ratio of CRN, both N uptake in plant and residual inorganic N in soil showed continuous increased trends and reached the highest values of 234.2 and 108.1 kg·hm^-2 in the CRN30% and CRN45% treatments, respectively, which were 18.0% and 45.1% higher than those in the CRN0% treatment, respectively. Nevertheless, apparent N loss decreased with increasing mixed ratio of CRN, and therefore led to reduced apparent N surplus. The lowest apparent N surplus was 114.4 kg·hm^-2 in the CRN30% treatment, which was reduced by 38.4% compared with the CRN0% treatment. In the treatments with mixed application of CRN, inorganic N contents were higher significantly in topsoil (0-30 cm) but lower in subsoil (60-90 cm) than that in the CRN0% treatment, indicating that less N was leaching down when mixed CRN was applied. The average results throughout two growing seasons showed that: Apparent N recovery rate increased significantly from 50.1% in the CRN0% treatment to 69.4% in the CRN30% treatment, and apparent N residual rate increased significantly with mixed application of CRN, while apparent N loss rate decreased significantly from 37.3% in the CRN0% treatment to 6.0% in the CRN45% treatment. 【Conclusion】 The mixed application CRN and urea is not only conducive to improve grain yield and N uptake of spring maize, but also to maintain a higher soil inorganic N content and reduce N loss, therefore resulting in increased N fertilizer use efficiency. Under the current condition, the appropriate mixed ratio of CRN for spring maize production in Northeast China is around 30% when 185 kg N·hm^-2 is applied.