氮负载生物炭对干湿交替稻田水土生态环境的调控效应

Effects of Nitrogen-loaded Biochar on Ecological Environment of Water and Soil in an Alternate Wet-dry Irrigated Paddy Field

农田面源污染已成为引起水体富营养化的主要原因之一。为了减少稻田氮素流失、改善稻田局部水体养分负载过重的问题,采用盆栽试验,通过生物炭吸附富营养水中的养分后再利用于盆栽水稻,设置主区为持续淹水灌溉(I F)与干湿交替灌溉(I A),副区为1个对照(常规施氮,N1C0)与4种不同用量的氮肥与氮负载生物炭处理(N3/4C1、N3/4C2、N1/2C1、N1/2C2),其中N3/4、N1/2表示氮肥施入量为当地传统施氮量(N1)的3/4,1/2倍;C1、C2分别为10 t/hm^2和20 t/hm^2氮负载生物炭。结果表明:(1)减少氮肥施入配施氮负载生物炭显著提高了常规施氮处理田面水的pH;(2)常规施氮肥处理下,干湿交替灌溉(I A)田面水NH 4^+-N平均浓度较持续淹水灌溉(I F)高8.0%,但是添加20 t/hm^2氮负载生物炭后,干湿交替灌溉田面水NH 4^+-N平均浓度低于持续淹水灌溉处理;(3)水稻生育后期,氮负载生物炭对NH 4^+-N具有明显的缓释作用,而在干湿交替灌溉中,减施氮肥配合添加氮负载生物炭处理较N1C0处理降低了田面水NO 3^--N浓度;(4)减施氮肥配合添加氮负载生物炭可提高水稻分蘖率,而添加20 t/hm^2氮负载生物炭在氮肥施用量较少时,有利于提高水稻的有效分蘖率。综上,氮负载生物炭不仅可以降低富营养水中30.8%含氮量,还能显著降低施肥初期水稻田面水中NH 4^+-N浓度,降低流失风险,延长NH 4^+-N的释放时间而减少1/4的施氮量和保证水稻生育末期的氮素需求,从而有利于水稻生长。

Farmland non-point source pollution has become one of the main causes of water eutrophication.In order to reduce nitrogen loss and relieve the over loading of nutrients in the local water body of rice field,a pot experiment was carried out.The main plots were continuous flooding irrigation(I F)and alternate wet and dry irrigation(I A),and the subplots were a control(conventional nitrogen application,N1C0)and four different nitrogen and nitrogen-loaded biochar treatments(N3/4C1,N3/4C2,N1/2C1,N1/2C2),in which N3/4 and N1/2 represented that the nitrogen application amount was 3/4 times and 1/2 times of the local traditional nitrogen application amount(N1);C1 and C2 were respectively 10 t/hm^2 and 20 t/hm^2 nitrogen-loaded biochar.Results showed that:(1)The pH value of the surface water with the conventional nitrogen treatment was significantly increased by reducing the application of nitrogen fertilizer and nitrogen-loaded biochar;(2)The average concentration of NH 4^+-N in the surface water of I A was 8.0%higher than that of I F,but the average concentration of NH 4^+-N in the surface water of I A was lower than that of I F after adding 20 t/hm^2 nitrogen-loaded biochar;(3)In the later growth stage of rice,the nitrogen-loaded biochar had a significant slow-release effect on NH 4^+-N,while in I A,the reduction of nitrogen fertilizer combined with nitrogen-loaded biochar reduced the concentration of NO 3^--N in the surface water compared with the treatment of N1C0.(4)The tillering rate of rice could be increased by reducing nitrogen application and adding nitrogen-loaded biochar,while the effective tillering rate of rice could be improved by adding 20 t/hm^2 nitrogen-loaded biochar when the amount of nitrogen application was less.In summary,reducing nitrogen application combined with adding nitrogen-loaded biochar could not only reduce the nitrogen content by about 30.8%in eutrophic water,but also significantly reduced the NH 4^+-N concentration in surface water at the early stage of fertilization,reduced the risk of loss,prolonged the release time of NH 4^+-N,reduced the nitrogen application amount by 25%and ensured the nitrogen demand at the end of rice growth,which was conducive to rice growth.