Transpiration of maize under different cultivation patterns in the Loess Tableland

Stem sap flow is a valuable plant water transportation parameter, meticulously indicating crop inner body water budget and driving natural growth of plants. Basic research on stem flow has not been completely enough in guiding dryland farming operations. It is therefore important to determine how stem flow reflects crop water balance under different cultivation models and to determine the relationship between water transport, cultivation pattern and environmental conditions. Sap flow rates of maize (Zea mays L.) under two cultivation patterns (traditional treatmentⅠ: "Shendan 16" at 45 000 plant·hm^-2 and N 225 kg·hm^-2 without mulching; improved treatmentⅡ: "Zhengdan 958" at 60 000 plant·hm^-2 and N 225 kg·hm^-2 and P₂O₅ 112.5 kg·hm^-2 with mulching) were continually measured by stem flow gauges (operated on heat balance method) along with combined environmental factors such as solar radiation, air temperature, and relative humidity to analyze variations in maize transpiration in the Loess Plateau. The results showed obvious maize sap flow rates in rhythm of daily variation as same as the radiation. Plants under treatment I had higher stem flow rate than those under treatmentⅡ. The maximum daily sap flow rates of maize were at tasseling stage, with values dropping at latter growth stages under the two cultivation treatments. This variation was also coincident with leaf area index. From tasseling to waxing stage, maize transpiration under treatmentsⅠandⅡwere respectively 115.18 mm and 119.47 mm. Compared with treatmentⅠ, soil evaporation under treatmentⅡdecreased by 39.2%. This implied that treatmentⅡoptimized the ratio of soil evaporation to maize evapotranspiration and improved WUE of the crop. Plant sap flow rates were affected by varied environmental factors, among which solar radiation was a critical meteorological factor. Daily sap flow rate per maize was significantly correlated with solar radiation, air temperature, vapor pressure deficit and relative humidity under both cultivation treatments.