太湖地区稻田土壤养分淋洗特征

通过排水采集器(Lysimeter)模拟试验，研究了太湖地区不同施肥水平下稻季农田养分淋洗特点。结果表明，施肥后田面水NH4^+-N浓度升高很快，2～3d达到峰值，最高值达26．2mg·L^-1，随后下降很快，这一周期约7～10d，渗漏水中NH4^+-N浓度很低，稻季NH4^+-N淋洗的氮仅占施肥量的0．008％～0．074％,渗漏液中NO3^--N含量随着氮肥用量的增加而增加，其浓度范围在0～7．14mg·L^-1，在土壤剖面中呈上低下高的趋势，稻季氮素的淋洗仍以NO3^--N为主，净淋洗量在3．2～8．3kg·hm^-2之间，占总施肥量的1．40％～2．78％,田面水磷浓度在施磷肥后1d即达最高值，随后下降，下层渗漏液中T-P含量很低，几乎不受施肥量的影响,猪粪能促进磷的迁移。

Characteristics of nutrient leaching from paddy field in Taihu Lake area

In recent years, excessive nutrient loss in subsurface drainage from agricultural land is identified as a major source of non-point source pollution, and has been attended globally. This study was conducted to determine the effect of nutrient leaching from paddy field in rice-planting season under different fertilizer application levels on water quality by using Lysimeter experiment. The results showed that the concentration of NH4(+)-N in surface water raised quickly after fertilization, reached the highest in 2 or 3 days with the maximum value of 26.2 mg.L-1, and then, dropped quickly within 7 or 10 days. The concentration of NH4(+)-N in leachate was very low, only accounted for 0.008%-0.074% of total fertilizer applied. The nitrate content in the solution and lossed from leaching increased gradually with fertilizer application rate, with a range from 0 to 7.14 mg.L-1. The nitrate concentration in leachate over the soil profile was characterized by a gradual increase from the top to bottom. Nitrogen was leached away mainly in the form of NO3(-)-N in rice-planting season, and the net NO3(-)-N loss was 3.2-8.3 kg.hm-2, accounted for 1.40%-2.78%. Under the experiment level, nitrogen leaching may lead to a potential pollution of underground water. The concentration of phosphorus in surface water reached the highest in one day after fertilization, after then dropped. The concentration of phosphorus in lower depth was very low, almost not affected by the amount of fertilizer applied. Application of pig manure could increase the transfer of phosphorus.