The response of three drybean cultivars to different phosphorus fertilizer rates and environmental conditions

Abstract

Drybean is a grain legume, which, through biological nitrogen fixation, is important to humans and animals as a valuable nutrient and for the improvement of the soil. Research was conducted to establish the response of three drybean cultivars to varying application rates of phosphorus fertilizer and to varying environmental conditions. The study was conducted during the 2017/2018 planting season at three locations, namely Taung, Mafikeng and Ventersdorp, in the North West province of South Africa that differed in terms of their environmental conditions. The research examined three drybean cultivars (PAN 123, PAN 148 and PAN 9292) at three sites (Taung, Ventersdorp and Mafikeng), and under five application rates of single superphosphate fertilizer, which differed according to each location (Taung = 0, 30, 45, 60 and 75 kg P/ha⁻¹, Ventersdorp = 0, 45, 60, 75 and 90 kg P/ha⁻¹ and Mafikeng = 0, 110, 114, 118 and 120 kg P/ha⁻¹). All the treatment combinations were laid out in a randomized complete block design (RCBD); with four replications. The assessed growth parameters include plant height, the number of leaves per plant, the chlorophyll content of the leaves, the quantity of nodules and the root length. The results from the research confirmed that PAN 9292 presented with the tallest plants and a larger range of nodules per plant than the other cultivars. PAN 123 produced a larger quantity of leaves per plant, higher chlorophyll content and longer roots length. The results of the research additionally confirmed that the drybean planted at Taung produced stronger growth parameters compared to the other location. The results further revealed that while the grain quality of PAN 123 was higher in ash and crude fibre content, PAN 148 had higher starch content and PAN 9292 had a better fat content. However, none of the cultivars confirmed any significant effect on drybean protein content. The interaction of cultivar × location had a significant effect at the drybean starch content. Chapter 1 presents an introduction and background to the study, focusing on the problem statement, a justification for the study and the aims and objectives of the study. Chapter 2 covers the literature review of the study. Chapter 3 includes the materials used and the methods applied, as well as the effects of phosphorus fertilizer rate, cultivar and location on drybean growth parameters, while Chapter 4 deals with the effects of phosphorus fertilizer rate, cultivar and location on drybean yield. Chapter 5 is about the effects of phosphorus fertilizer rate, cultivar and location on the grain quality of the drybean. Chapter 6 concludes with a discussion on the research findings and recommendations based on the results of the study.