Effect of in-field water harvesting with different mulching practices on crop response

[摘要] It is well known that in semi-arid areas the growth and yield response of crops depend largelyon the amount of rainwater stored in the root zone. Integrating rainwater harvesting andmulching may be an approach to maximize water storage and to minimize water lossesthrough evaporation and runoff. This may improve crop growth and yield. A two year studywas conducted to determine the effect of an in-field water harvesting with mulch applicationin both the basins and runoff strips on growth and yield response of maize (Zea mays L.) andsunflower (Helianthus annus L.).The experiment was conducted at the Glen experimental farm, 25 km north Bloemfontein(28055'l3 latitude and 26°21 '12 longitude) on a heavy clay soil (Bonheim soil form). Itconsisted of four mulching treatments. Three of the mulching treatments were a combinationof rainwater harvesting basin (RWHB) with organic mulch in the basin and organic (00) orstone (OS) mulch on the runoff strip or bare runoff strips (OB). The fourth treatment was thecombination of RWHB with stone mulch in the basin and organic mulch on the runoff strips(SO). The organic mulch was a mixture of maize and sunflower stalks at the rate of 8 t.ha-I.The size of the stones in the mulch was approximately 10 to 15 cm in diameter, and theycovered 70-80 % of the soil surface.Two adjacent, 24 m x 36 m (288 m²), experimental sites were used to accommodate the fourtreatments in a completely randomized block design with three replications. Maize, varietyPhb 33-V08 and sunflower, variety SNK 74 were planted in a tramline with spacing 1m x 2mon the 7th and 28th of January 2000 and the 5th and 4th of January 2001. respectively. During thetwo seasons, maize and sunflower were grown in rotation, whereas treatments were maintainedin place. The soil water content, rainfall and evaporation demand of the atmosphere were evaluatedfrom the data obtained from ARC-ISCW (Glen). Plant height and stem thickness at maturitywere measured to determine whether growth was stimulated or inhibited. Stem growth rates and leaf area indexes were determined during 209°/2001 to evaluate early growth responses ofthe tested crops. The aerial biomass and grain yield of maize and sunflower were also assessed.The two seasons were different with respect to the amount and distribution of the rainfall. soilwater patterns and evaporative demand of the atmosphere. The 1999/2000 growing season wasmore favourable for crop growth and yield than 2000/2001.Results of soil water measurements showed that the applications of stone or organic mulch onthe runoff strips were beneficial to conserve water in the soil profile of the runoff stripsirrespective of crop type. Although it is not always significant, organic mulch placement on therunoff strip reduced the amount of water stored in the basins. This effect was not observedwhen the runoff strips were mulched with stones.'Although not statistically significant, the growth and yield of maize were higher in OS, SO and00 treatments than in the control (OB). Maximum biomass and grain yield over seasons wasobtained in the OS. All plant parameters studied showed that the interaction between mulchingand seasons had no significant influence on the growth and yield of maize. Althoughdifferences were not always statistically significant, the OS technique seemed to be the best forcrop growth and yield. Similar results were obtained for sunflowers, which was regarded as anadvantage for farmers enabling them to exercise maize-sunflower rotation without changingmulching practices.

[发布机构] University of the Free State