| Based on the Water Conservation Project II financed by World bank in Shanxi Province,the fields irrigated insufficiency of different typical landscape,different crops and different soil water sources were used as research contents,in order to gradually form water resource management mode basing on crop evapotranspiration(hereinafter referred to as ET),more scientific and rational control and reduce water consumption remainder in field crop and develop agriculture with saving water in irrigation.ET of field farmland under the natural,irrigation and supplying from ground water condition were annual follow-up monitored.The values of ET at a variable and the water productivity at a variable and non-sufficient water supply condition were calculated.The annual track the monitoring data basis for this article include soil moisture content,bulk density,irrigation water amount,rainfall and temperature.The crop evapotranspiration and crop water productivity were respectively analyzed and calculated according to three different soil water sources of rain,irrigation and groundwater recharge.The conditions concluded only rainfall,both rainfall and irrigation,and rain,irrigation and groundwater recharge.The typical landscape such as hill,basin,mountain and river-beach were considered.The land use pattern such as farmland,grassland and fruit forest were considered.The agronomic measures such as straw returning and plastic film mulching were considered.It aims to reveal the change rule of crop evapotranspiration both under the natural and artificial conditions.The main findings and conclusions are as follows:(1)The characteristics of the crop evapotranspiration under the condition of only rainfall replenishment.The phase variation of crop evapotranspiration during growth period presented a certain similarity under three different land use modes such as cultivating spring maize,economic fruit and natural grassland on the Loess plateau.It was mainly represented: the diurnal variation cure of evapotranspiration showed a tendency first increasing and then decreasing with the advance of plant growth stage and reached maximum value in August when temperatures are the highest and the rainfall are the most concentration.Therein,evapotranspiration of spring maize was 281.99 mm,the maximum value of evapotranspiration intensity was 3.22mm/d and the water production efficiency was 1.86 kg/m3 during whole growth period.Evapotranspiration of economic fruit in the mountainous and arid area was 262.75 mm and the maximum value of evapotranspiration intensity was 3.26mm/d.Evapotranspiration of natural grassland in the shady slope of mountainous was 395.60 mm and the maximum value of evapotranspiration intensity was 4.36mm/d.On account of lacking of soil moisture for it supplying by only rainfall,the crop evapotranspiration of three different land utilizations was low under the condition of rainfall.(2)The characteristics of the crop evapotranspiration under the condition of rainfall and irrigation water replenishment.The slopes of crop accumulative evapotranspiration curve of spring corn irrigated,winter wheat and spring corn on the river beach changed with the advance of plant growth.They were relatively small at early growth stages,relatively big at middle growth stages and the curve slowed at end growth stages.It indicated intensity of crop evapotranspiration increased first and then decreased with time during whole growth period and peaked at middle growth stages.Therein,evapotranspiration of spring corn irrigated was 346.08 mm,the maximum value of evapotranspiration intensity was 6.6mm/d and the water production efficiency was 2.20 kg/m3.Evapotranspiration of winter wheat was 387.71 mm and the maximum value of evapotranspiration intensity was 6.51mm/d and the water production efficiency was 1.60 kg/m3.Evapotranspiration of spring corn on the river beach was 428.86 mm and the maximum value of evapotranspiration intensity was 5.96mm/d and the water production efficiency was 2.27 kg/m3.Compared with the condition of only rainfall replenishment,the soil moisture was relatively plentiful,water consumption of crop evapotranspiration increased and the water production efficiency significantly improved.(3)The characteristics of the crop evapotranspiration under the condition of rainfall,irrigation water and groundwater replenishment.The accumulative evapotranspiration of vegetables in the field was linear basically with growth period.It was 563.36 mm and the average of the intensity of evapotranspiration was 2.72mm/d during whole growth period.The daily intensity of evapotranspiration of spring corn on the river beach experienced three periods of improving steadily,rising rapidly and declined gradually.The maximum value of evapotranspiration intensity appearing in December was 7.06mm/d,the accumulative evapotranspiration was 521.42 mm and the water production efficiency was 2.56 kg/m3.Compared with the condition of only rainfall replenishment and considerations of rainfall and irrigation,groundwater replenishment was added to the source of soil moisture.Therefore,the value of evapotranspiration and daily intensity of evapotranspiration both were obviously improved.It shown groundwater replenishment had a greater impact to evapotranspiration and the water production efficiency significantly improved.(4)The characteristics of the spring corn evapotranspiration under three different agronomic practices of permeable film,ordinary plastic film and non-mulching plastic film.In each growing stage,all of the value of the accumulative evapotranspiration of spring corn were smallest under the condition of permeable film than that of ordinary plastic film and non-mulching plastic film except in August when spring corn are at their most vigorous.The change regulations of the intensity of evapotranspiration were similar under three different agronomic practices.The value of evapotranspiration increased gradually at early growth stages,increased quickly at middle growth stages and inclined gradually at end growth stages.Under the condition of non-mulching plastic film,evapotranspiration of spring corn was 246.40 mm and the water production efficiency was 1.80 kg/m3.Under the condition of ordinary plastic film,evapotranspiration of spring corn was 238.47 mm and the water production efficiency was 1.96 kg/m3.And evapotranspiration of spring corn was 232.24 mm and the water production efficiency was 2.15 kg/m3 under the condition of permeable film.The agronomic practice of plastic film could effectively reduce water consumption of crop evapotranspiration and the effect of permeable film was more obvious than that of ordinary plastic film.The benefits of water-saving and product-enhancing were better.By studying crop evapotranspiration under the natural and artificial conditions,the change rule of evapotranspiration of different crops was revealed during growth period.Water use characteristic of crop evapotranspiration was mastered irrigated insufficiency.It provides technical support for agricultural production practice in cultivated soils on Loess plateau. |
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