Response of Chia (Salvia Hispanica) to Water Stress, Plant Density and Nitrogen Fertilizer in Two Agro-ecological Zones of Kenya

Abstract

Chia (Salvia hispanica) is gaining popularity worldwide due to its nutritional and health benefits. In Kenya, production of chia seed is relatively new, and the crop has gained attention hence prompting the possibility of its production within diverse agro ecological zones. Optimal production practices of the crop are partially understood. This study involved three main objectives. The first objective was to determine the effect of varying soil moisture regimes on the growth and yield of chia. The second objective determined the effect inter-row spacing on growth and yield of chia in contrasting agro-ecological zones of Kenya. The third objective evaluated the effect of different rates of nitrogen fertilizer rates on growth and yield of chia two agro-ecological zones of Kenya. The first objective of the study was carried out in the greenhouse for two experimental cycles, while the second and third objectives were carried out in open fields for two growing seasons. In the first objective, treatments comprised four moisture regimes, 40%, 60%, 80% and 100% field capacity in a randomized complete block design with three replications. A potting media of soil, sand and well- decomposed cow manure was prepared in the ratio of 2:1:1 w/w, respectively. Plastic potting bags of 8 kg capacity were filled with media, and five chia seeds sown and later thinned to three plants per pot. In a random sample of five pots per treatment plot, five chia plants were tagged for data collection. Significant variations were observed, with higher plant height, leaf traits, and yield components observed in moisture regimes of 80% and 100% field capacity. Chia plants were significantly (p<0.05) taller under 80% and 100% FC compared with 40% and 60%. Highest grain yields greater than 20 g/plant were observed upon an increase of field capacity from 60% to 100%. Field experiments were conducted in Nyeri and Kabete for two seasons in a randomized complete block design in three replications. The influence of different row spacing on chia growth and yield was assessed. It comprised of three rows spacing of 30 cm x 10 cm, 60 cm x 10 cm and 90 cm x 10 cm. In each plot, 5 plants were randomly selected and tagged for data collection. No significant found among the evaluated row spacing treatments. For the third objective, treatments comprised of five nitrogen rates namely; 0 kg N/ha, 25 kg N/ha, 50 kg N/ha, 75 kg N/ha, and 100 kg N/ha. Urea was applied in two splits of 2 and 6 weeks using the drill method 5cm close to the crop rows then covered with soil lightly. In each plot, 5 plants were randomly selected and data on crop phenology growth and yield were assessed, recorded and analyzed. Plant height for both sites was highest at the treatments subjected to 50 kg N/ha. Yield components including grain yield, biomass, test weight defined as a measure of how much a specific volume of harvested crop weighs, and harvest index were highest at N-application rate of 50 kg N/ha. Application of N- fertilizer of 100kgN/ha resulted in more vegetative growth at the cost of seed setting during xii reproductive phase thus affecting grain yield. The results revealed that chia performed better in well irrigated soils. However, remarkable yield was realized in treatments under 40% FC and thus the crop can be grown in regions experiencing low rainfall. It is important to note that while row spacing may not have a significant direct impact on the growth and yield of chia, other factors such as nutrient availability, water management, pest and disease control, and overall agronomic practices can still play crucial roles in maximizing chia crop. While varying nitrogen fertilizer application rates showed limited impact on chia growth and yield, it's crucial to exercise caution to prevent over application. This not only leads to excessive vegetative growth and reduced seed formation but also contributes to resource wastage, making it economically unsustainable in agricultural practices. Overall, these findings contribute to a better understanding of chia cultivation practices and provide insights for optimizing chia production in different environments