甘肃秦王川灌区种植豆禾混播牧草的农田生态保育效应

以裸地(CK)、种植小麦(Triticum aestivum)和苜蓿/无芒雀麦(Medicago sativa/Bromus inermis)豆禾混播牧草地为研究对象,通过测定地表植被特征指标、土壤风蚀量及理化性质等指标,探究秦王川灌区农田风蚀规律及种植春小麦和牧草对土壤及养分流失的影响。结果表明:农田表土损失呈秋末冬初流失较多,冬季较少,春季又明显增强的"U"形曲线模式,从9月至翌年6月,出现2个风蚀高峰期(9—11月和3—5月);耕地裸露造成表土年均流失1.7 kg/m~2,即每年被风吹蚀1.3 mm厚表土,土壤有机质损失236.2 kg/hm~2,而种植小麦和牧草后在地表植被(根茬)覆盖作用下表土流失减少20.1%和52.3%,有机质损失减少12.2%和50.7%;由于风蚀季牧草植被(根茬)的盖度、高度和地表生物量均较小麦大,使得牧草地的地表粗糙度和湿度及表土(0—5 cm)含水率较小麦地高,从而造成土壤和有机质流失较小麦地少;相关和回归分析显示,地表植被特征指标与地表粗糙度和土壤含水率间呈显著正相关,而与地表土壤和有机质流失量呈极显著负相关;植被盖度每提高1%,将使表土和有机质流失减少4.1 g/m~2和59.3 mg/m~2,地表生物量每提高1 g/m~2,将使表土和有机质流失减少2.3 g/m~2和34.0 mg/m~2;春季春播小麦地的表土流失量与裸地相同,而种植多年生豆禾混播牧草可显著减少表土流失和有机质损失。综合以上,甘肃灌区农田春季播种农作物易引起土壤退化,而种植多年生豆禾混播牧草可实现农田生态保育,从而提高耕地质量和区域环境质量。

Ecological Conservation Effect of Mixed Planting Legume and Grass in Qinwangchuan Irrigation Area of Gansu Province

To explore wind erosion law of farmland and effects of planting spring wheat and pasture on soil and nutrient loss, the experiment took bare land (CK), planting Triticum aestivum and Medicago sativa/Bromus inermis farmland as research objects. We measured indexes of vegetation characteristics, soil wind erosion, and physical and chemical properties. The results showed that soil loss showed a ''U'' curve pattern, with more loss in late autumn and early winter, less loss in winter, and significantly increased loss in spring. There were two peak periods of wind erosion (September to November and March to May) from September to June of the following year. The average annual soil loss of bare land was up to 1.7 kg/m², that was, as 1.3 mm thick topsoil was blown away by wind, resulting in the loss of land organic matter up to 236.2 kg/hm². When wheat and pasture were planted, the soil mass loss reduced by 20.1% and 52.3%, and the organic matter loss reduced by 12.2% and 50.7% under the influence of surface vegetation (stubble). Due to the higher coverage, height, and surface biomass of pasture vegetation (stubble) than those of wheat in wind erosion season, the surface roughness, humidity, and water content of topsoil (0-5 cm) of grassland were higher than those of wheat field, resulting in less soil and organic matter loss than that of wheat field. Correlation analysis showed that there were a significant positive correlation between vegetation characteristics and surface roughness and soil moisture content, while there were a significant negative correlation between vegetation characteristics and surface soil and organic matter loss. Regression analysis showed that every 1% increase of vegetation coverage would reduce topsoil and organic matter loss by 4.1 g/m²and 59.3 mg/m². Every 1 g/m² increase of surface biomass would reduce topsoil and organic matter loss by 2.3 g/m² and 34.0 mg/m². The amount of topsoil loss of wheat fields sowed in spring was the same as that of bare land, while planting perennial legume-grass mixtures could significantly reduce the loss of topsoil and organic matter. On the whole, crops sowed in spring in irrigated areas of Gansu would likely cause soil degradation, while planting perennial legume-grass mixtures could fulfill the farmland ecological conservation, improve quality of cultivated land and regional environment.