Feng-Xin Wang

Potato evapotranspiration and yield under different drip irrigation regimes

A field experiment comparing different irrigation frequencies and soil matric potential thresholds on potato evapotranspiration (ET), yield (Y) and water-use efficiency (WUE) was carried out in a loam soil. The experiment included five treatments for soil matric potential: F1 (-15xa0kPa), F2 (-25xa0kPa), F3 (-35xa0kPa), F4 (-45xa0kPa) and F5 (-55xa0kPa) and six treatments for irrigation frequency: N1 (once every day), N2 (once every 2xa0days), N3 (once every 3xa0days), N4 (once every 4xa0days), N6 (once every 6xa0days) and N8 (once every 8xa0days). Results indicate that both soil matric potential and drip irrigation frequency influenced potato ET, Y and WUE. Potato ET increased as irrigation frequency and soil matric potential increased. Comparing soil water potential, the highest ET was 63.4xa0mm (32.1%) more than the lowest value. Based on irrigation frequency treatments, the highest ET was 36.7xa0mm (19.2%) more than the lowest value. Potato Y and WUE were also found to increase as irrigation frequency increased. Potato Y increased with an increase in soil water potential then started to decrease. The highest Y and WUE values were achieved with a soil matric potential threshold of -25xa0kPa and an irrigation frequency of once a day.

Untangling the effects of shallow groundwater and deficit irrigation on irrigation water productivity in arid region: New conceptual model

Water scarcity and salt stress are two main limitations for agricultural production. Groundwater evapotranspiration (ETg) with upward salt movement plays an important role in crop water use and water productivity in arid regions, and it can compensate the impact of deficit irrigation on crop production. Thus, comprehensive impacts of shallow groundwater and deficit irrigation on crop water use results in an improvement of irrigation water productivity (IWP). However, it is difficult to quantify the effects of groundwater and deficit irrigation on IWP. In this study, we built an IWP evaluation model coupled with a water and salt balance model and a crop yield estimation model. As a valuable tool of IWP simulation, the calibrated model was used to investigate the coupling response of sunflower IWP to irrigation water depths (IWDs), groundwater table depth (GTDs) and groundwater salinities (GSs). A total of 210 scenarios were run in which five irrigation water depths (IWDs) and seven groundwater table depths (GTDs) and six groundwater salinities (GSs) were used. Results indicate that increasing GS clearly increases the negative effect on a crops actual evapotranspiration (ETa) as salt accumulation in root zone. When GS is low (0.5-1g/L), increasing GTD produces more positive effect than negative effect. In regard to relatively high GS (2-5g/L), the negative effect of shallow-saline groundwater reaches a maximum at 2m GTD. Additionally, the salt concentration in the root zone maximizes its value at 2.0m GTD. In most cases, increasing GTD and GS reduces the benefits of irrigation water and IWP. The IWP increases with decreasing irrigation water. Overall, in arid regions, capillary rise of shallow groundwater can compensate for the lack of irrigation water and improve IWP. By improving irrigation schedules and taking advantages of shallow saline groundwater, we can obtain higher IWP.

Precision Drip Irrigation on Hot Pepper in Arid Northwest China Area

An experiment was conducted to study the effects of different soil water potential (SWP) on soil water content, hot pepper’s yield, water consumption and water use efficiency (WUE) under plastic-mulched drip irrigation in the North-West China in order to find a suitable SWP to guide the pepper irrigation. Five treatments were set based on SWP, they are -10kPa (N1), -20kPa (N2), -30kPa (N3), -40kPa (N4) and -50kPa (N5). A control treatment (N6) was set based on local irrigation practice, i.e. border irrigation. SWP was measured using tensiometers at 0.2 m depth immediately under drip emitters. Pepper leaf area, plant height, soil water content, yield and total soluble solid (TSS) were measured, soil water content and water use efficiency were calculated. Results shows that the differences in leaf area index and plant height are not significant (P>0.05) among treatments of N1, N2, N3 and N4. While the pepper yields, WUE and TSS are higher for treatments N3 and N4. Controlling SWP at -50kPa greatly decreases crop yield and WUE. Therefore, we recommend -30 ~ -40 kPa as the irrigation threshold for pepper cultivation under mulched drip irrigation in arid areas of the North-West China.