Timing of weed control and harvest date effects on potato crop field performance and mineral content.

Abstract

Potato (Solanum tuberosum) is an important vegetable crop that is high on dietary minerals and vitamins that are needed by the human body but can be a weak competitor to weeds. The aim of the study was to determine the effect of weeds and harvest period on plant growth, yield and mineral content of tubers. The experiment was conducted at the University of KwaZulu-Natal’s Ukulinga farm. The experiment had three weeding treatments namely control weed free, weed free till flowering stage then stop and no weeding. And two harvest periods which were early (90 days after planting) and late (120 days after planting). The crop was monitored from emergence using phenological (plant height and leaf number) and physiological (Leaf area index, Chlorophyll content index, photosynthetically active radiation, stomatal conductance) parameters during the growing stage prior to flowering. At harvest, the number of tubers, size of tubers and plant biomass were recorded to determine the yield. After yield determination the potato samples were taken to the laboratory for mineral content analysis. The results showed that there was a significant difference (p<0.05) in the weeding treatments with respect to the phenological parameters. The control weed free treatment had the highest plant growth and yield while the no weeding treatment had the lowest plant growth and yield. It was also observed that the early harvested tubers were smaller in size while the tubers harvested late were larger in size. This is because the tubers harvested late were given enough time to grow and mature. Harvesting early under the no weeding treatment resulted in significantly lower yields due to the decrease in tuber mass. There were significant effects of weed control and harvest timings with respect to mineral content in tubers. Potassium was found to be the dominant mineral element followed by phosphorus. These elements were found in levels that were up to 100 times higher than those of calcium, magnesium and sodium in potato tubers. It is concluded that delaying weed control reduces crop performance, yield and mineral content. However, delaying harvest time may provide an opportunity for the crop to accumulate more weight and mineral content in the tubers. Keywords: Chlorophyll content index, Tubers, Biomass, Leaf area index, Photosynthetically active radiation, mineral content, yield.