黄绵土不同形态有机氮径流流失规律

Different Forms of Organic Nitrogen Loss in Soil by Runoff in Slope Land of Loess Plateau

利用不同坡度径流小区 ,在自然降水条件下 ,研究侵蚀泥沙不同形态有机氮的流失规律 ,结果表明 :在 4次产流泥沙中 ,除氨基糖氮含量减少外 ,其它有机形态氮均存在增加趋势 ,以氨态氮含量增加最为显著。随坡度的下降 ,水解全氮、氨态氮和氨基酸氮含量呈增加趋势 ;泥沙中水解全氮、氨基酸氮、氨态氮、非酸水解氮均存在不同程度的富集 ,其富集率随坡度的下降而增大 ,以氨基酸氮富集程度高 ,泥沙中氨基糖态氮反而无富集现象存在 ;当坡度分别为 2 5°、2 0°、15°、10°和 5°时 ,水解全氮流失量分别为 1135 .0、76 3.7、485 .5、313.0和 15 4.4kg/ km2 ,而氨基酸氮流失量则为 2 34.8、182 .7、12 1.1、76 .8和 33.9kg/ km2 ,占水解全氮的 2 0 .6 %～ 2 4.9%。氨态氮流失量为 742 .5、5 0 3.3、32 2 .2、2 0 8.9、97.4kg/ km2 ,占水解全氮的 6 3.1%～ 6 6 .7%。氨基糖氮占酸水解氮 1.1%～ 2 .9%。非鉴别氮占水解全氮的 5 .8%～ 12 .6 %。而酸水解氮与非酸水解氮之比分别为 1.5、1.5、1.4、1.8和 2 .3。

Under natural rainfall condition, the regular pattern of soil organic nitrogen loss by runoff was investigated. The results showed that except for that the content of amino sugar reduced in sediment, the other forms of organic N were increased compared with local soil. With slope gradient falling, the contents of hydrolyzable N, amino acid N, and ammonia N were increased. The hydrolyzable N, amino acid N, ammonia N, and unidentified N existed in enriching phenomenon in sediment, the enrichment ratios of these organic nitrogen were increased with slope gradient falling, but, the amino acid N has a higher enrichment ratio than other organic N, on the contrary, the content of amino sugar N in sediment was lower than local soil. The loss amounts of hydrolyzable N were 1135.0 in 25°, 763.7 in 20°, 485.5 in 15°, 313.0 in 10°and 154.4 kg/km 2 in 5°. The loss amounts of amino acid N were 234.8, 182.7, 121.1, 76.8 and 33.9 kg/km 2 separately, accounting for 20.5%～24.9% of hydrolyzable N. The loss amounts of ammonia N were 742.5, 505.3, 322.2, 208.9 and 97.4 kg/km 2 respectively, accounting for 63.1%～ 66.7% of hydrolyzable N. The loss amounts of amino sugar N accounted for 1.1%～2.9% of hydrolyzable N. The loss amounts of unidentified N accounted for 5.8%～12.6% of soil total N.