摘要
以河沟流域沟坝地为研究对象,分析比较了沟坝地土壤特征,结果表明:(1) 沟坝地土壤为粘层和壤层有韵律的交替分层剖面,粘层在上、壤层在下的土体结构并非上松下紧。粘层的物理性粘粒含量55 % ～60 % ,壤层为35 % ～50 % ,粘层厚度从坝前至坝后逐渐变薄。(2)坝地土壤容重、田间持水量、吸湿水明显高于塬面、塬坡土壤,而水分稳渗率却低于塬面、塬坡。(3) 坝地土壤水分含量高于塬面、坡面的含水量,从坝前至坝尾逐渐增高。土壤水分动态变化与降雨量有直接关系,7 ～9 月降水较大时,坝地土壤含水量经常处于饱和或接近饱和状态,特别在坝尾常常形成湿地草甸或沼泽地。(4) 坝地淤积土壤在未种植之前养分含量低于塬面、塬坡土壤,其中土壤全氮、速效氮、速效磷和有机质更加偏低,且土壤养分含量从坝前至坝尾逐渐减少。据此提出沟坝地易涝、速效养分特别是氮相对缺乏的观点,建议坝地种植过程,特别是种植初期,采取有效的排水措施,加强春季晒垡,注重施肥特别是氮肥,以保障沟坝地高产稳产。
Focus on the damland in Hegou watershed, the soil characteristics of the damland were analysed. The results show that: (1) Soil section in damland alternates clay layer and loam layer with rhyme, the clay is upper and loam is lower, not upper layer is loose and lower is tight.The physical clay particle content of the clay layer is 55%~60%,and that of the loam layer is 35%~50%. The thickness of clay layer get smaller and smaller from upper reaches to lower reaches. (2) The soil bulk density, water holding capacity and moisture of absorption in damland is obviously higher than those in yuanmian (viz. upper table) and slope, while the stable water infiltration rate is lower than that in yuanmian and slope. (3) The water content in damland is higher than that in yuanmian and slope , and it increases from damhead to damtail.The dynamic changes of soil water is directly related to precipitation, which in July to September is bigger, especially in the damtail, the damland is often water logged or forms grassy marshland. (4) The nutrient content of the dam silt soil is less than yuanmian and slope,the total nitrogen, quick acting nitrogen ,quick phosphorus and organic matter of silt are much lower, and they decrease from damhead to damtail. Therefore, the damland is liable to water logging and lack of quick acting nutrient, especially nitrogen. It is suggested that adopting effective drainage measures, strengthening sunning the upturned soil in spring, paying attention to applying fertilzer, especialy to nitrogenous fertilizer, so as to ensure high and stable yield of the damland, especially initial planting stage.
基金
国家"八五"科技攻关项目!85- 01 -008 -11
国家"九五"科技攻关项目!96- 004- 05 -06
