土壤表层管理对稻田土壤氮矿化势、固氮强度及铵态氮的影响

 耕作管理对土壤表层（0-15cm）氮矿化势（N#-0）平均值无明显影响，但对N#-0在0-15cm表层的垂直分布有显著影响。表层配合施用有机无机肥，比纯施化肥显著提高了0-15cm的N#-0值。0-15cm土层N#-0与稻麦产量呈显著相关。免耕土壤NH#+(+)#-(4) -N前期强度大，水稻易早发。两种耕作管理下土壤平均固氮强度（Ⅰ）无明显差异，且多数处理Ⅰ值至水稻拔节期达到高峰。在水稻营养生长期，无肥区Ⅰ值约为其它施肥的2-10倍。土壤NH#+(+)#-(4) -N对土壤固氮活性起抑制作用的初始浓度为20ppm，Ⅰ与N#-0在水稻生长期间有明显相关性。

EFFECTS OF SOIL SURFACE MANAGEMENTS ON N MINERALIZATION POTENTIAL,NON-SYMBIOTIC N FIXING INTENSITY AND AMMONIUM N IN A PADDY SOIL

The mean N mineralization potential (N_0) in surface soil (0-15cm) was not significantly affected by tillage methods, which, however, markedly influenced the vertical distribution of N_0 in soil (0-15cm). Compared with single chemical fertilizer applied in soil, combined fertilizer with organic manure predominantly increased the N_0 in 0-15 cm soil layer, significant correlation was found between N_0 (0-5cm) and rice or wheat yields.The NH_4~+-N concentration of no-tillage (N-T) plot was greater than that of conventional tillage (C-T) plot at the early stage, which resulted in an earlier flourish of rice with N-T.There was no remarkable difference between the average N-fixing intensity (I) of C-T and N-T, and it was found that the peak of I occurred at rice jointing stage in most treatments of both tillage method. The I value in check plot (no fertilizer) was 2-10 times the size of fertilized locations during rice vegetative periods.The least concentration of NH_4~+-N in soil was about 20 ppm which could inhibit the activity of N-fixing. Close correlations existed between N_0 (0-5cm) and I values during rice growth.