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 and N 225 kg·hm without mulching; improved treatmentII: “Zhengdan 958” at 60 000 plant·hm and N 225 kg·hm and P2O5 112.5 kg·hm 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 treatment I, 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. 第 4期 王淑庆等: 黄土塬区不同栽培模式下玉米蒸腾耗水规律的研究 433

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 P 2 O 5 112.5 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 treatment Ⅰ, 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.

Fig. 1 2 不同栽培模式下玉米茎流速率与太阳辐射的日变化Fig. 2
Fig. 1 Rainfall distribution during maize growth stage in the experiment period

Fig. 3
Fig. 3 Variation of daily sap flow rate of maize during different growth stages under different cultivation patterns 表 1 不同栽培模式下不同生育期玉米蒸腾耗水量

图 5 玉米生育期茎流速率与气象因子的变化Fig. 5
Fig. 5 Variations of maize stem sap flow rate and meteorological factors at different maize growth stages

Table 1
Transpiration of maize at different growth stages under different cultivation patterns ET: filed evapotranspiration; T: leaf transpiration.

Table 2
Pearson correlation between daily stem sap flow rate of maize and meteorological factors during maize growth stages SR: solar radiation; VPD: vapor pressure deficit; RH: relative humidity; T a : air temperature; V w : wind speed; **表示 0.01 水平上显著相关 ** means significant correlation at 0.01 probability level.