Leaf and seed yield response of vegetable amaranths to nitrogen fertilizers applications and harvesting frequency at Jimma, South West, Ethiopia

Abstract

Amaranthus (Amaranthus cruentus) is an alternative food crop that requires fewer agronomic practices relative to other food crops. However, the yield of Amaranthus varies due to factors such as season, soil fertility, variety, and management practices. There is limited information available on certain agronomic practices for Amaranthus, such as harvesting frequency and N fertilizer application rates. The objective of this study was to determine the effects of nitrogen levels and harvesting frequencies on the growth, leaf and seed yield, and yield components of the Amaranth Madiira-2 cultivar at Jimma, under irrigation. The study used a randomized complete block design with a factorial arrangement of five N levels (0, 34.5, 69, 103.5, and 138) and three harvesting frequencies (weekly, every 2 weeks, and every 3 weeks), replicated three times. Data on phenological growth, yield, and yield components were collected and analysed using SAS software (version 9.3). The results revealed that the combined effect of nitrogen and harvesting frequency significantly influenced (p < 0.05) the days to 50% flowering and days to 50% physiological maturity. Leaf area, plant height, above-ground fresh weight, above-ground dry weight per plant at harvest, leaf yield, and seed yield were highly significantly influenced (p < 0.01). However, the thousand seed weight when a two-week harvesting frequency was followed after transplanting and 103.5 kg N ha−1 was applied. The leaf yield was found to be significantly influenced by the harvesting frequencies, with the highest yield of 30.33 tons ha−1 observed under this particular combination of factors. Similarly, the seed yield was also maximized at 3.23 tons ha−1 under the same conditions, with 103.5 kg N ha−1 and a three-week harvesting frequency. Therefore, these findings suggest that farmers can benefit from applying 103.5 kg N ha−1 with a two-week harvesting frequency for better leaf yield and 103.5 kg N ha−1 with a three-week harvesting frequency for better seed yield. However, it is important to note that this study was conducted only during one season and in one location. Hence, conducting the experiment again in real-world settings, across various seasons and locations, would be beneficial. This would allow for drawing more reliable conclusions and making appropriate recommendations.