Quantitative analysis of irrigation water productivity in the middle reaches of Heihe River Basin, Northwest China

With the growing shortage of surface water resources,it is of great significance for improving the irrigation water productivity(IWP)to ensure the water and food security.The contribution of the driving factors of the IWP and the rational regulation of the input factors of agricultural production is required.In this paper,118 and 80 sampling points were selected in Pingchuan and Liaoquan irrigation districts(PLID,the spacing of sampling point is approximately 1 km)and the middle reaches of the Heihe River basin(MHRB,the spacing of sampling point is approximately 10 km),respectively.Soil characteristics and management measures near the sampling points were obtained.Results showed that the average value of the IWP in MHRB was 1.67 kg/m3,with a moderate heterogeneity in the space.The main driving factors of IWP were irrigation,fertilization and planting density.On the PLID,the contribution rates of soil factors and management measures to IWP were 20.6%and 35.2%,respectively,and the contribution of soil factors to IWP increased to 43.8%in the MHRB,while the contribution rate of management measures decreased to 24.8%.It shows that in a small irrigation districts,from the perspective of farmers,the improvement of IWP should be mainly controlled by management measures,while in the large area of watershed scale,the spatial differences in soil factors also need to be considered by the government management departments,when they want to increase IWP through regulating management measures.

The effects of aeration and irrigation regimes on soil CO_2 and N_2O emissions in a greenhouse tomato production system

Aerated irrigation has been proven to increase crop production and quality, but studies on its environmental impacts are sparse. The effects of aeration and irrigation regimes on soil CO2 and N2O emissions in two consecutive greenhouse tomato rotation cycles in Northwest China were studied via the static closed chamber and gas chromatography technique. Four treatments, aerated deficit irrigation（AI1）, non-aerated deficit irrigation（CK1）, aerated full irrigation（AI2） and non-aerated full irrigation（CK2）, were performed. The results showed that the tomato yield under aeration of each irrigation regime increased by 18.8% on average compared to non-aeration, and the difference was significant under full irrigation（P〈0.05）. Full irrigation significantly increased the tomato yield by 23.9% on average in comparison to deficit irrigation. Moreover, aeration increased the cumulative CO2 emissions compared to non-aeration, and treatment effects were significant in the autumn-winter season（P〈0.05）. A slight increase of CO2 emissions in the two seasons was observed under full irrigation（P〉0.05）. There was no significant difference between aeration and non-aeration in soil N2O emissions in the spring-summer season, whereas aeration enhanced N2O emissions significantly in the autumn-winter season. Furthermore, full irrigation over the two seasons greatly increased soil N2O emissions compared to the deficit irrigation treatment（P〈0.05）. Correlation analysis indicated that soil temperature was the primary factor influencing CO2 fluxes. Soil temperature, soil moisture and NO3^- were the primary factors influencing N2O fluxes. Irrigation coupled with particular soil aeration practices may allow for a balance between crop production yield and greenhouse gas mitigation in greenhouse vegetable fields.

Fertilizer drawn forward osmosis as an alternative to 2nd pass seawater reverse osmosis: Estimation of boron removal and energy consumption

Agriculture is the largest consumer of freshwater.Desalinated seawater is an important alternative water source for sustainable irrigation.However,some issues of the current desalination technology hinder its use for agriculture irrigation,including low boron removal and high energy consumption.This study systematically explored the feasibility of employing fertilizer drawn forward osmosis(FDFO)as an alternative to 2nd pass reverse osmosis(RO)by considering the boron removal performance and specific energy consumption(SEC).Different operating conditions were investigated,such as the boron and NaCl concentrations in feed solution(FS),draw solution(DS)concentration,pH,the volume ratio of FS to DS,membrane orientation,flow rate,and operating temperature.The results indicated that a low boron concentration in FS and high DS pH(pH=11.0)decreased the boron solute flux,and led to low final boron concentration in the DS.The other operating conditions had negligible influence on the final DS boron concentration.Also,a lower flow rate and higher specific water flux with certain permeate water volumes were conducive to reducing the SEC of the FDFO process.Overall,our study paves a new way of using FDFO in irrigation,which avoids the phytotoxicity and human health risk of boron.The results show the potential of FDFO as an alternative to 2nd pass RO for irrigation water production.