Evaluating the effectiveness of a hydrophobic polymer for conserving water and reducing weed infection in a sandy loam soil

In this work we tested the influence of different solutions of a hydrophobic polymer named Guilspare®, applied to the soil surface to reduce soil evaporation, on the soil water status, soil temperature, crop performance and weed emergence. Two tests were carried out on a farm of the Guadalquivir river valley, southwest Spain, one with a maize crop and the other with bare soil. In the test with maize, we evaluated the effect of applying a solution of 2% v/v of Guilspare® in water, at the rate of 3 l m−2, on the crop performance and weed emergence. On both the treated and the untreated control plots, three rates of irrigation were applied, namely 100, 75 and 50% of the locally determined optimal irrigation depth to cover the crop needs for an optimum development and yield. For the case of 50% of the irrigation dose, the performance of the crop treated with the polymer (T50) was much better than that of the untreated control plot (C50). The crop height and green leaf area index for T50 were nearly as good as for the C100 control plants receiving 100% of the irrigation dose. The T50 crop was 73% of the yield of the treated and fully irrigated T100 crop, while the C50 yield was only 38% of the C100 yield. The treated crop reached the different phenological stages quicker than the untreated crop. The polymer was effective in reducing weed emergence. In the test with bare soil, 0.8% v/v of Guilspare® in water, at the rate of 1 l m−2, kept levels of water content in the soil as high as other solutions with greater amounts both of polymer and water. The average soil water content during the irrigation period in this lower treatment was 34 and 53% higher at depths of 0.15 and 0.25 m, respectively, than in the untreated plots. No influence of the polymer on soil temperature was observed. Results from additional measurements on weed emergence and hydraulic conductivity of the soil surface showed that the polymer was still effective 7 months after application. In fact, the hydraulic conductivity in the range near saturation was 44% greater in the treated plots than in the untreated ones, and the number of weeds was 27% lower.