Study On Soil Water Characteristics Of Laboratory Soil Column Experiment Planted Wheat With Different Planting Densities

According to capillary theory, soil water characteristic curve (SWCC) actually reflectsthe relationship between soil pore condition and soil water content. So any factor whichinfluences soil pore will lead to the change of SWCC. Root widely exists in the soil. Root caninsert, push the soil and stretch in it. This will significantly affect different size soil pore’sdistribution and connectivity. Laboratory soil column experiment planted wheat with differentdensities was conducted. Soil water characteristic curve, saturated water content and capillarywater in0-40cm soil layers were measured layer-by-layer. Gardner model was used todescribe SWCC. SWCC, water-holding capacity and water-supplying capability of differentplanting densities were studied. The results showed that:1) Soil water characteristic curveThere is an obvious inflection point of SWCC when soil water suction is about100kPa.The curve is relatively flat when soil water suction is less than100kPa, while itbecome steeper when soil water suction is greater than100kPa.There are significantdifferences between the treatments and the control. When the soil water suction is less than100kPa, there is significant difference of the slop of the curve between each treatment. Whensoil water suction is greater than100kPa, only treatment E is steeper than others in0-20cmsoil layer.With the same planting density, there are some differences between different soil layers.The difference is more obvious with larger planting density.2) Soil water-holding abilityWater-holding capacity of different soil layers showed similar trends. Soil water-holdingcapacity decreased minimum and then increase with increasing planting density of wheat. Inaddition, with the same planting density, the differences of soil water holding ability inshallow layers are more obvious.3) Soil water-supplying capacityIn0-20cm soil layers, soil water-supplying capacity decrease with increasing plantingdensity of wheat. In20-40cm soil layers, soil water supplying capacity decreased minimumand then increase with increasing planting density of wheat. On the other hand, with the sameplanting density, soil water supplying ability in shallow layers is weaker. With the increase of soil suction the specific water capacity was sharply decreased and ithad already reduced to10-2cm~3/cm~3·bar at soil suction-0.4bar. When soil water potential islarger than-0.4bar, the specific water capacity is larger and soil can supply a large amount ofwater. When soil water potential reduced to-2.5bar, the specific water capacity becamesmaller obviously, water amount which soil can supply became less. When soil waterpotential is smaller than-10bar and larger than-15bar, the water content still belongs toavailable water, while it can be used difficultly.4) Equivalent pore volumeCompared with the control treatment, macrospores (d>0.05) increased greatly,micropores（0.0002mm<d<0.005）and residual pores(d<0.0002mm) reduced to a certainextent.