Effect of a new antitranspirant on the physiology and water use efficiency of soybean under different irrigation rates in an arid region

Antitranspirants are exogenous substances applied to leaves to reduce luxury transpiration by regulating stomatal conductance to increase water use efficiency(WUE). A cheap and environmentally-friendly antitranspirant, FZ, was newly developed, extracted mainly from Alhagi sparsifolia. Its effects on soybean water use were investigated in a field experiment using the locally-used irrigation rate and a low irrigation rate(The lower and upper limit of irrigation is 40%–70% of field capacity). Foliar application of FZ and measurement of leaf physiological characteristics, final biomass, seed yield and water use efficiency were carried out during the pod bearing and pod filling stages of drip-irrigated soybean with film-mulching. Under the low irrigation rate, leaf stomatal conductance(gs) and transpiration rate(Tr)decreased significantly by 7 d after spraying, but photosynthesis(Pn) and instantaneous water use efficiency(WUE_(in)) were not significantly affec ted. The stomatal frequency, stomatal aperture, gs, Tr and Pn decreased by 1 d after spraying, without significantly increasing WUE_(in).However, applying FZ during the pod bearing and pod filling stages did not significantly affect the final biomass,water consumption, seed yield and WUE of soybean.Under the locally-used irrigation rate, applying FZ increased the activities of superoxide dismutase and peroxidase in the leaves by 38% and 33%, respectively,but did not significantly affect gs, Tr, Pn, stomatal aperture and stomatal frequency. Applying FZ three times during pod bearing and pod filling stages enhanced seed yield and WUE by 24% and 21%, respectively, but did not significantly affect the final biomass and water consumption. Therefore, seed yield and WUE of soybean were significantly increased by foliar application of FZ during the pod bearing and pod filling stages under the locally-used irrigation rate in arid region, but applying FZ did not have a positive effect on water use efficiency of soybean under a low irrigation rate.

Comparison of evapotranspiration and energy partitioning related to main biotic and abiotic controllers in vineyards using different irrigation methods

Knowledge of evapotranspiration(ET)and energy partitioning is useful for optimizing water management,especially in areas where water is scarce.A study was undertaken in a furrow-irrigated vineyard(2015)and a drip-irrigated vineyard(2017)in an arid region of northwest China to compare vineyard ET and energy partitioning and their responses to soil water content(SWC)and leaf area index(LAI).ET and soil evaporation(E)and transpiration(T)were determined using eddy covariance,microlysimeters,and sap flow.Seasonal average E/ET,T/ET,crop coefficient(Kc),evaporation coefficient(Ke),and basal crop coefficient(Kcb)were 0.50,0.50,0.67,0.35,and 0.29,respectively,in the furrow-irrigated vineyard and 0.42,0.58,0.57,0.29,and 0.43 in the dripirrigated vineyard.The seasonal average partitioning of net radiation(Rn)into the latent heat flux(LE),sensible heat flux(H)and soil heat flux(G)(LE/Rn,H/Rn,and G/Rn),evaporative fraction(EF)and Bowen ratio(β)were 0.57,0.26,0.17,0.69 and 0.63,respectively,in the furrowirrigated vineyard and 0.46,0.36,0.17,0.57 and 0.97 in the drip-irrigated vineyard.The LE/Rn,H/Rn,EF,andβwere linearly correlated with LAI.The E,Kc,Ke,E/ET,LE/Rn,LEs/Rn(ratio of LE by soil E to Rn),H/Rn,EF andβwere closely correlated with topsoil SWC(10 cm depth).Responses of ET and energy partitioning to the LAI and SWC differed under the two irrigation methods.Drip irrigation reduced seasonal average E/ET and increased average T/ET.From the perspective of energy partitioning,seasonal average H/Rn increased whereas LE/Rn,especially LEs/Rn,decreased.Compared with furrow irrigation,drip irrigation decreased the proportion of unproductive water consumption thereby contributing to enhanced water use efficiency and accumulation of dry matter.