垄作对降低黄土高原南部冬小麦田氨挥发风险的影响

为研究黄土高原南部冬小麦田NH₃挥发对垄作的响应,揭示其释放机制及污染风险,于2011—2013年冬小麦生长季,按照随机裂区试验设计布置田间试验,采用通气式田间原位酸吸收方法测定NH₃挥发. 主区为常规栽培及3种垄作,副区为2种施N(氮)处理——未施N(0 kg/hm2,以N计)和施N(180 kg/hm2). 结果表明:不同施N处理下,各耕作模式NH₃挥发通量在施肥后10 d均达到峰值,在施肥后30 d稳定在较低水平. 垄作单季NH₃累积挥发量(以N计)平均值为5.748 kg/hm2,比常规栽培降低4.9%；施N处理下NH₃累积挥发量平均值为6.512 kg/hm2,比未施N处理提高26.8%. 氮肥NH₃挥发损失率为0.47%~1.38%,其中垄作平均损失率比常规栽培降低60.1%. 不同施N处理下,各耕作模式NH₃挥发通量与土壤w(NH₄+)、含水量呈正相关；与25 cm深度处土壤温度、pH在冬前(施肥播种至土壤结冰阶段)呈正相关,而在冬后(土壤解冻至小麦收获阶段)则呈负相关. 土壤w(NH₄+)和土壤温度是控制NH₃挥发的两大主要因素. 冬前垄作降低NH₃挥发通量主要是由于垄作集中深施肥会增加NH₃挥发扩散阻力所致. 可见,旱作冬小麦种植区采用垄作可降低NH₃挥发风险. 

Effects of Ridge Tillage Practices on Reducing Ammonia Volatilization from Winter Wheat Fields in Southern Loess Plateau of China

Abstract: This study aims to assess the response of ammonia (NH₃) volatilization to ridge tillage practices in a winter wheat (Triticum aestivum L.) field in the southern Loess Plateau, China. A two-year field experiment was conducted from 2011 to 2013 in the winter wheat growing seasons. The experiment was designed as a split-plot style with tillage practices as main plots. There were three ridge tillage practices and conventional tillage (CT) as the control. Nitrogen application rates were subplots, namely 0 and 180 kg/hm². Ammonia volatilization was trapped using vented acid trapping methods, and ammonium (NH₄⁺-N) was measured using a continuous flow analyzer. Relationships between NH₃ flux and five soil parameters were analyzed by linear regression and stepwise multiple linear regression. The parameters were soil NH₄⁺, moisture, temperature, pH and organic carbon. The results showed that NH₃ flux peaked during the first 10 d following fertilizer application, reduced rapidly in the next 20 d and then leveled off. Ammonia emissions in the ridge tillage systems were on average 5.748 kg/hm²,4.9% less than that in CT (6.05 kg/hm²). In treatments fertilized with 180 kg/hm² nitrogen fertilizer, ammonia emissions averaged 6.512 kg/hm²,6.8% greater than the unfertilized plots. Nitrogen loss rates varied from 0.47% to 1.38%, and the average loss rate in the ridge tillage systems was 60.1% lower than that in CT. Ammonia flux was positively correlated with soil NH₄⁺ and moisture. Ammonia flux was positively correlated with soil temperature and pH from October to December. However, it was negatively correlated with the variables from February to June. Overall, soil NH₄⁺ and temperature were two major factors controlling NH₃ flux in winter wheat fields. The extent of ammonia fluxes linked to soil NH₄⁺ was significantly reduced by ridge tillage practices. Therefore, extending ridge tillage practices is recommended in rain-fed winter wheat production in the southern Loess Plateau to mitigate NH₃ volatilization. Further verifications with multi-location tests could be required to further investigate the effects on NH₃ volatilization of ridge tillage systems and different nitrogen application rates.