不同包膜控释尿素对农田土壤氨挥发的影响

为了探索包膜控释尿素土壤氨挥发损失规律特征和提高肥料氮素利用率,采用小麦玉米轮作田间试验,通过与普通尿素进行对比,运用土壤氨挥发原位测定方法——通气法系统研究了硫包膜和树脂包膜控释尿素的施用对小麦玉米轮作农田土壤氨挥发的影响.研究结果表明:在两种施氮量水平下(210 kg/hm2和300 kg/hm2),与普通尿素相比,硫包膜和树脂包膜控释尿素在小麦基肥期、小麦追肥期和玉米施肥期的施用均减少了土壤氨挥发的累积损失量,分别达35.1％-54.3％、59.6％-75.2％、65.6％-98.1％；有效降低了土壤氨挥发通量峰值且延迟其出现时间3-8 d,并能延缓土壤氨挥发主要阶段的时间分别为4-12 d、5-12 d.在小麦玉米轮作周年中,控释尿素土壤氨挥发累积损失量为28.39-43.35 kg/hm2,土壤氨挥发损失率为4.48％-5.63％,控释尿素时段土壤氨挥发通量比普通尿素降低了51.0％-70.8％；且树脂包膜控释尿素的施用降低小麦玉米轮作农田土壤氨挥发的效果优于硫包膜控释尿素.

Effects of different coated controlled-release urea on soil ammonia volatilization in farmland

Nitrogen fertilization has become one of the important components of agricultural management to guarantee high and stable crop production. China has only 7% of the world's arable land but consumes 35% of the global nitrogen fertilizer. Nitrogen fertilizers are used excessively and the nitrogen use efficiency is only 20%-40%. Apart from some residuals remaining in the soil, most of the excess nitrogen enters the air or water sources, and therefore causes serious environmental pollution. Ammonia volatilization is an important pathway through which nitrogen is lost to the atmosphere. Identifying methods to reduce the ammonia volatilization of nitrogen fertilizer is an important task for agricultural management. Given the increasing prominence of China's food and environmental safety, improvements in agricultural management are important. The application of controlled-release urea fertilizers may be one of the most effective measures to solve the problems of high fertilizer usage and low efficiency rate that leads to pollution.A field experiment was conducted to evaluate the effects of controlled-release urea coated with sulfur or with polymer on soil ammonia volatilization in a wheat-corn rotation system. The venting method was used for the in situ determination of ammonia volatilization from October 2008 to October 2009 at a Huang-Huai-Hai region test site. The results showed that the flux and the accumulated loss of ammonia with the controlled-release urea fertilizers were significantly lower than those with the common urea fertilizer when the fertilizers were applied at 210 kg/hm² or 300 kg/hm², and at the wheat basal, wheat top dressing and maize fertilization stages. The time to reach 80% of total loss of nitrogen through ammonia volatilization with the controlled-release urea fertilizer coated with sulfur and with polymer was 4-12 and 5-12 days longer, respectively, than that with the common urea fertilizer at the fertilizer rate of 210 kg/hm².During the wheat growth season, the soil ammonia volatilization flux with the two controlled-release urea fertilizers increased slowly, and their flux peaks were significantly lower (by 1.6-3.3 kg·hm^-2·d^-1) and later (by 3-8 days) than those with the common urea fertilizer. The time ammonia volatilization flux(193 days) and the accumulated loss amounts of ammonia volatilization over this period with the controlled-release urea fertilizers were significantly lower than those with the common urea fertilizer. The flux and the loss amounts were both lower by 45.4%-61.0%. The ammonia volatilization loss rate of the controlled-release urea fertilizers was lower than that of the common urea fertilizer by 4.7%-5.7%. The soil ammonia volatilization flux peak when using the sulfur-coated controlled-release urea fertilizer was earlier and higher than that when using the polymer-coated controlled-release urea fertilizer. The accumulated ammonia loss amounts when using the sulfur-coated controlled-release urea fertilizer was higher (by 5.8%-10.7%) than that when using the polymer-coated controlled-release urea fertilizer.During the maize growth season, the soil ammonia volatilization flux peaks with the two controlled-release urea fertilizers were later (by 3-5 days) and the peaks lower (by 1.9-5.2 kg·hm^-2·d^-1) than those with the common urea fertilizer. The ammonia volatilization flux peak when using the sulfur-coated controlled-release urea fertilizer was higher than that when using the polymer-coated controlled-release urea fertilizer; it increased by 76.9% and 12.2% under the high and low levels of nitrogen fertilizer (300 and 210 kg/hm²), respectively. The time ammonia volatilization flux (67 days) and the accumulated loss amounts of ammonia volatilization when using the two controlled-release urea fertilizers were both lower (by 65.6-98.1%) than that when using the common area fertilizer. The ammonia loss rates were also lower by 2.7%-3.3%. The accumulated loss amounts with sulfur-coated fertilizer was higher than those with polymer-coated fertilizer by 19.7% at the fertilizer rate of 300 kg/hm²; however there was no significant difference at the rate of 210 kg/hm².During the wheat-corn rotation growth period, the controlled-release urea fertilizers coated with polymer or with sulfur was able to significantly reduce the time ammonia volatilization flux and loss rate. The time flux was 0.11-0.17 kg/(hm²·d) over the whole period (260 days). The total loss amount of the soil ammonia when using the controlled-release urea fertilizers (coated with sulfur or with polymer) was 28.39-43.35 kg/hm², which was lower than that of the common urea fertilizer by 51.0-70.8%. The loss rate of soil ammonia of the controlled-release urea fertilizers was 4.48%-5.63%, which was lower (by 3.7%-4.5%) than that of the common urea fertilizer.Based on our findings, controlled-release urea fertilizers can significantly reduce soil ammonia volatilization, and therefore may cause less pollution than common urea fertilizers. The controlled-release urea fertilizer coated with polymer was found to have more desirable properties than the controlled-release urea fertilizer coated with sulfur.