米林县不同种植年限蔬菜大棚土壤pH和无机氮变化特征研究

为阐明露地与不同种植年限大棚土壤pH值及无机氮含量变化特征,给保护性耕作土壤的可持续利用提供科学依据,以米林县不同种植年限蔬菜大棚(1 a、4 a和6 a)和相邻露地为研究对象,研究了露地和不同种植年限蔬菜大棚(0~20 cm表层)和(0~70cm剖面)土壤无机氮浓度及pH值分布特征。结果表明:土壤硝态氮浓度表现为,1 a大棚4 a大棚6 a大棚露地;铵态氮浓度表现为,6 a大棚4 a大棚露地1 a大棚;pH值分布为,1 a大棚露地4 a大棚6 a大棚。随着剖面土壤层次的加深,大棚土壤硝态氮及矿化氮浓度呈降低趋势,露地土壤硝态氮浓度呈先增加后降低的趋势,露地土壤铵态氮及矿化氮浓度呈先降低后增加的趋势;与露地相比,大棚土壤铵态氮、硝态氮浓度及pH值具有更大的垂直空间变异性。土壤pH值随土壤深度的增加,露地表现为逐渐增加的趋势,而蔬菜大棚呈先降低后增大的趋势。大棚土壤pH值与硝态氮和铵态氮含量之间存在负相关,露地土壤pH值与硝态氮和铵态氮含量之间存在正相关关系。在林芝区域大棚生产过程中,表层土壤酸化现象加重,且增加了土壤无机氮的积累,故在生产管理中宜适当减少氮肥的供应。

Research on the variation characteristics of pH and mineral nitrogen concentrations in different planting time polytunnel soils of Milin County in Tibet

In order to elucidate variation characteristics of soil pH and mineral nitrogen(Nmin) concentrations between open fields and different planting time polytunnel fields, then provide scientific support for the sustainable utilization of soil in Tibet area. Different planting time polytunnel(1 a, 4 a and 6 a) and there adjacent open fields in Milin County were investigated, surface soil(0~20 cm depth) and profile soil(0~70 cm depth) were collected, and the soil nitrate nitrogen(NN) and ammonium nitrogen(AN) concentrations and pH were determined. The results showed that, Soil NN concentrations had the decrease sequences as 1 a polytunnel > 4 a polytunnel > 6 a polytunnel > open field; soil AN concentrations were 6 a polytunnel > 4 a polytunnel > open field >1 a polytunnel; and soil pH were 1 a polytunnel > open field > 4 a polytunnel > 6 a polytunnel; Compared to the open field soil, the soil NN and Nmin concentrations in polytunnel soils increased in 0~20 cm arable layer, and they were all decreased with the increase of soil depth; Compared to open field soil, pH decreased for 0~20 cm polytunnel soil, and then increased with the increase of soil depth; Regression analysis showed a negative correlation between soil pH to NN and AN concentrations for polytunnel soils; but for the open field soil, they were negatively correlated. These results indicated that polytunnel management resulted in soil acidification of arable layer, and increase of soil Nmin; so the application of nitrogen fertilizer need be reduced for polytunnel soil.