不同农田防护林配置结构下玉米水分来源研究

Study on the Moisture Source of Maize Under the Configuration Structure of Different Farmland Shelterbelts

由于气候条件干旱,合理平衡防护林与农田作物水分需求是河套灌区农田防护林林网体系建设的关键问题。为研究河套灌区典型农田防护林对农田作物水分来源的影响,选择河套灌区3种典型配置的防护林系统,测定并分析附近农田距农田边缘0.3,0.4,0.6,2 H处土壤含水率、土壤和作物茎秆水氢氧同位素值。结果表明:(1)7—9月各农田样地土壤含水率普遍较低,4,5行样地在近林端处土壤含水率均低于远林端处,8行样地各处土壤含水率没有明显差异。(2)各样地土壤水氢氧同位素随着土层深度的增加而贫化,其中,8行样地距农田边缘0.4~0.6 H处40—60 cm土层的土壤出现较大的同位素富集。(3)4行样地内距农田边缘0.3~0.4 H处玉米主要利用40—80 cm土层土壤水,0.6~2 H处玉米利用0—40 cm土层土壤水。5行样地0.3 H处玉米利用20—60 cm土层土壤水,0.4~2 H处玉米利用0—60 cm土层土壤水。8行0.3,2 H处玉米主要利用0—40 cm土层土壤水,0.4~0.6 H处玉米则更多地利用20—80 cm土层土壤水。研究认为,8行配置的防护林对农田作物水分利用范围影响更广,在不影响防护效果的前提下,4,5行防护林对农田作物生长用水影响范围更小。研究结果可为当地合理配置农田防护林体系提供理论参考。

It is a key problem to balance the water demand of shelterbelt and farmland crops reasonably in the construction of shelterbelts forest network system in Hetao irrigation district due to the arid climate conditions.In order to study the influence of typical farmland shelterbelts on the water source of farmland crops in Hetao irrigation district,three typical shelterbelt systems in Hetao irrigation district were selected,and the soil moisture content,hydrogen and oxygen isotope values of soil and crop stem water at 0.3 H,0.4 H,0.6 H and 2 H away from the edge of nearby farmland were measured and analyzed.The results showed that:(1)From July to September,the soil moisture contents of all farmland plots were generally low.The soil moisture contents of 4 and 5 row plots at the near end of forest were lower than that at the far end of forest,and there was no significant difference in the soil moisture content of the 8 row plots.(2)The hydrogen and oxygen isotopes of soil water in all plots were depleted with the increase of soil depth as a whole.Among them,the 40—60 cm soil layer at 0.4~0.6 H away from the edge of farmland in the 8 row plots showed greater isotope enrichment.(3)The soil water of 40—80 cm soil layer was mainly used for maize at 0.3~0.4 H away from the edge of farmland in the 4 row plots,and the soil water of 0—40 cm soil layer was used for maize at 0.6~2.0 H.The soil water of 20—60 cm soil layer was used for maize at 0.3 H and the soi lwater of 0—60 cm soil layer was used for maize at 0.4~2.0 H in row 5 plots.The maize in row 8 at 0.3 H and 2 H mainly used soil water in 0—40 cm soil layer,while the maize at 0.4~0.6 H mainly used more soil water in 20—80 cm soil layer.According to the study,the shelter forest with 8 row configuration had a wider impact on the water use range of farmland crops,while the influence range of 4 and 5 row of shelterbelts on the growth water of farmland crops was smaller on the premise of not affecting the protection effect.The results can provide theoretical reference for the rational allocation of farmland shelterbelt system.