Effect of Nitrogen Rates and Sources on Plant Growth, Yield, Quality and Nitrogen Use Efficiency on African Nightshade Varieties (Solanum spp) in Kenya

Abstract

The increasing demand for African nightshade (Solanum spp) as a nutritious leafy vegetable in Kenya underscores the need for optimizing its agronomic practices to enhance production sustainability. Nitrogen, a critical nutrient, significantly influences plant growth, yield, and quality of African nightshade. However, the efficiency of nitrogen use and its impact vary depending on its rate and source. The objective of this study was to determine the effects of nitrogen rates and sources on growth, yield, vegetable quality and nitrogen use efficiency of African Nightshade (Solanum villosum and Solanum Scabrum) species. Understanding these dynamics will inform best practices for nitrogen management, thereby contributing to improved crop productivity and sustainable agricultural development. Two pot experiments were conducted in a green house at Jomo Kenyatta University of Agriculture and Technology between December 2016 and November 2017. The experiments were laid out in a complete randomized design with four treatments replicated four times.The first experiment was on the effects of Nitrogen rates on African nightshade growth ,yield and quality.The treatments included 0g, 0.9g, 1.8g and 3.6g of CAN fertilizer per plant. Data collection was on plant height, number of leaves, fresh leaf weight, protein content, nitrate content and nitrogen use efficiency of Solanum villosum and Solanum Scabrum species. Protein and nitrate content were determined at vegetative and reproductive stages using semi-micro kjeldal and colorimetric methods respectively. Statistical analysis on the data indicated that nitrogen fertilizer application rates had a significant effect on plant growth, yield, quality and NUE at P≤0.05 level of significance. At the vegetative stage plants supplied with 3.6 g per plant of CAN had a higher protein and nitrate content at 28.4% and 2.6 mg/kg in Solanum villosum and 29.3% and 2.3mg/kg in Solanum scabrum species. At the reproductive stage Statistical analysis on proteins and nitrates indicated that nitrogen significantly affected nitrate content at P≤0.05. NUE efficiency was calculated according to Moll et al 1982, statistical analysis on the data determined that plants in the control group were the most nutrient efficient at P≤0.05 followed closely by plants supplied with 0.9g of CAN. In the second experiment different nitrogen sources was seen to affect plant growth yield, quality and NUE of African nightshade. The treatments included 0g, 2.11g(Urea),3.6g(CAN) and 36.4g (organic fertilizer) per plant. Experimental layout and data collection parameters were similar to the first experiment. Statistical analysis conducted on the data indicated that nitrogen sources significantly affected plant growth, yield, quality and NUE of African Nightshade at P≤0.05 level of significance. There was a significant difference in NUE at P≤0.05 with plants in the control group and those supplied with organic fertilizer having a higher NUE. Based on results of this study it is recommended that farmers use nitrogen rate of 3.6 g of (CAN) per plant which is equivalent to 400kg of CAN per HA to improve the growth and yield of African nightshade. While increasing nitrogen rates boosts vegetable yield, it is crucial to strike a balance between yield and quality. In order to increase yields in a more sustainable way farmers should implement a split application strategy for nitrogen fertilizer and incorporate organic sources so as to improve NUE, reduce costs and vegetable maintain quality. Keywords: Productivity, quality, nitrogen use efficiency, nitrates, protein.