紫色土丘陵区小流域不同土地利用方式土壤氮磷储量特征

Characteristics of Soil Nitrogen and Phosphorus Reserves of Different Land Use Modes of Small Watershed in Purple Hilly Area

[目的]了解紫色土丘陵区小流域不同土地利用方式下土壤氮磷特征。[方法]采集典型小流域林地、旱地、水旱轮作田的分层土壤样品,研究不同土地利用方式下土壤氮磷含量及储量变化,探讨土地利用方式对紫色土丘陵区小流域土壤氮磷库的影响。[结果]3种土地利用方式下,土壤全氮、硝态氮、全磷含量存在显著差异,相同土层土壤全氮含量表现为水旱轮作田>林地>旱地,旱地和水旱轮作田的硝态氮、全磷含量显著高于林地。土壤全氮、硝态氮、全磷含量均随土壤深度增加而下降,表现出明显的表聚性。土壤全氮储量表现为水旱轮作田(684 t/hm2)>旱地(448 t/hm2)>林地(372 t/hm2);土壤全磷储量与土壤全氮储量变化规律相似,水旱轮作田土壤全磷储量(389 t/kg)最高,其次是旱地(373 t/hm2)和林地(153 t/hm2);林地与旱地、水旱轮作田土壤硝态氮储量具有显著差异,且表现为旱地(104.68 kg/hm2)>水旱轮作田(79.70 kg/hm2)>林地(14.81 kg/hm2)。[结论]紫色土丘陵区林地土壤养分固持潜力较大,而耕地土壤氮磷等养分流失风险较高。

[Objective]To clarify the characteristic of soil nitrogen and phosphorus of different land use modes in the purple soil area of central Sichuan Basin. [Method] Soil samples were collected on soil profile for forest land, upland filed and paddy field from 27 sampling sites within a small watershed,and the variation of soil nitrogen and phosphorus contents and reserves of different land use modes was researched, and the effect of the land use modes on the soil nitrogen and phosphorus pools in the watershed of Central Sichuan Basin was identified. [Result]The contents of soil total nitrogen（STN）, nitrate nitrogen（NO 3 --N） and soil total phosphorus（STP） were significant influenced by land use modes, and the contents of STN in the same soil layer under different land use modes were as the following orders： paddy filed〉forest land〉upland field;and the contents of soil NO 3 --N and STP in paddy field and upland field were significantly higher than that in forest land. The contents of STN, NO 3 --N, and STP under different land use modes decreased with the increase of soil depth and showed obvious characteristic of surface accumulation. The stocks of STN under different land use modes were as the following orders： paddy filed （684 t/hm 2）〉upland field（448 t/hm 2）〉forest land（372 t/hm 2）;the STP stocks had the same trend as STN stocks, and the STP stocks was highest in paddy field（389 t/kg）, followed by upland field（ 373 t/hm 2 ） and forest land （153 t/hm 2）;the soil NO 3 --N stocks in forest land were significant different with the stocks in paddy field and upland field, and the NO 3 --N stocks were as the following order： upland field （101.68 kg/hm 2）〉paddy filed（70.70 kg/hm 2）〉forest land（14.8 kg/hm 2）. [Conclusion]The potential of soil nutrient sequestration was significant in forest land, especially for STN, and the risk of nutrient loss from upland field and paddy field was very high in the purple soil area of central Sichuan Basin.