The effect of water quality on the growth and yield of irrigated crops

[摘要] English: Salinity is a major limitation and threat sustainable crop production in South Africa andelsewhere in the world. An intensive study by Du Preez et al. (2000) on the water quality ofthe lower Vaal River system using international salinity indicators were conducted and it wasconcluded that unacceptable damage to crops would be experienced if the salinity of theirrigation water continued to increase at the projected rates. Following that, intensivegermination and glasshouse pot experiments were conducted based on the projected longtermsalt accumulation on irrigated soils. Little or no quantitative information on the subjectwas available for South African conditions. This study was also part of a WRC project titled:The effect of irrigation water salinity on the growth and water use of selected crops.The objective of this study was to quantify the effect of different saline irrigation water levels(electrical conductivity, ECi ) on the germination, growth and yield of selected crops, viz.wheat (Triticum aestivum L. - SST 806.), maize (Zea mays L. - PNR 6335), peas (Pisumsativum L. - Solara) and beans (Phaseolus vulgaris L. - Teebus) at different growth stages.These crops were subjected to five different ECi levels (15 - control, 150, 300, 450, 600 forwheat and maize, and additionally 1200 mSm-1 for wheat, and 15 - control, 75, 150, 225,300 mS m-1 for peas and beans). Three stages were used for each crop, viz. tillering, flag leafand maturity (wheat), 2, 4 and 6 wae - weeks after emergence (maize) and 5 wae - five weeksafter emergence, flowering and maturity (peas and beans).Various morphological indicators presented on a relative scale were measured to quantify theimpact of ECi levels on both below and above ground growth. When subjecting the crops tothe different ECi levels, the salt tolerance of these plants was taken into consideration. Thesecrops were affected at varying degrees, depending on the salt sensitivity of the crop involved.Interesting results were obtained for all the crops and based on the findings the study agreedwell with the international accepted salinity classification system where wheat is classified asmoderately tolerant and peas and beans as sensitive. Maize proved to be sensitive in thisstudy, but it has to be noted that it was only at a very early growth stage.The water use of the pot experiment plants was found to be very high and this was attributedto the smaller volume of soil relative to the canopy. All plant growth indicators proved to benegatively affected over the selected ECi range. The reduction in growth for all cropsfollowed a similar trend with increasing ECi levels. The EC of the saturation soil extract(ECe) was also measured in order to determine the rate of soil salinisation and was found tobe 2 to 3 times that of ECi. The study also compared the responses of these crops by usingprimary growth indicators (leaf area, root mass, biomass and seed yield) and also attemptedto determine the salt tolerance values using the regression coefficients. Therefore, all theobjectives set for the study were achieved. The effect of salinity on a variety of other cropsunder South African conditions should be thoroughly and comprehensively investigated infuture.

[发布机构] University of the Free State