Performance of selected soybean (Glycine max) varieties grown in Kalahari sands under different irrigation regimes

The increased demand for soybean (Glycine max (L.) Merrill) for human and animal consumption, vegetable oil extraction, and soil fertility improvement through biological nitrogen fixation has led to the expansion of its production to even marginal areas under rainfed farming systems. Production in dryland areas is constrained by drought, among other challenges. This study, therefore, sought to assess the performance of selected soybean varieties that were sourced locally and regionally and grown in Kalahari sands under different watering regimes before flowering. Seven soybean varieties (Kabanyolo 1, Maksoy 1N, Maksoy 4M, Namsoy 3N, Nam 1, Solitaire, and UG5) were studied for growth and yield performance under various watering regimes. The study was conducted at Lupane State University experimental plots. Soybean plants were grown in 9 l buckets arranged following a randomized complete block design with seven varieties in three blocks. Three irrigation regimes were used (soil saturation capacity, 50% soil saturation capacity, and 25% soil saturation capacity) up to flowering, after which the plants were sufficiently rainfed and supplemented through irrigation up to physiological maturity. Data were collected at physiological maturity (stem height, pod length, pods per plant, number of seeds per pod, nonviable pod percentage, 100-seed weight, and total grain weight per plant). Irrigation regimes and variety independently influenced most parameters that were assessed in soybeans. All the variables were significantly affected except for the % nonviable pod under the three irrigation regimes. Maksoy 4M, Nam 1, and Namsoy 3N performed better than the other varieties, while UG5 and Solitaire were the least performers in most of the variables measured. Irrigating to 50% soil saturation capacity and below suppressed growth and yield. Varieties that outperformed others can be used by breeders to improve their tolerance to pre-flowering drought stress