Effects of water and fertilizer stress on the yield, fresh and dry matter production of grain Amaranth (Amaranthus cruentus)

The effects of crop yield, fresh and dry matter partitioning of grain amaranth (Amaranthus cruentus) in relation to different water stress and different levels of fertilizer application were studied. Grain amaranth was planted in the predominantly sandy loam soil. The treatments applied include replenishing soil moisture back to field capacity and imposing moisture stress 75% and 50% of the amount of water applied to bring soil moisture to field capacity. Within each treatment were varying levels of fertilizer application based on plant density and influence area at 100%, 75% and 50%. The actual crop evapotranspiration (ETa) was determined by using a weighing lysimeter and the reference evapotranspiration (ETp) was determined by using the pan evapotranspiration method. The results showed that water had significant effect on the total plant weight, stem weight, leaf weight, and root weight with p-values of 0.000, 0.001 and 0.000 respectively. However fertilizer and its interaction with water had no significant effect on total plant weight, stem weight, and root weight with p-values of 0.15 and 0.75, 0.22 and 0.68, and 0.37 and 0.79 respectively. For total plant weight, root, leaf wet and dry weights however, fertilizer had significant effect with p- values of 0.04, 0.042, 0.011 and 0.039 for dry matter. None of water, fertilizer and their interactions had any significant effect on dry matter concentration and the harvest index of the plant and dry matter concentration of the partitioned components of the plant. Fresh matter accumulation increased with time for all the combinations until after the seventh week of planting beyond which fresh accumulation started reducing. Plots with moisture content kept at field capacity and 100% fertilizer application recorded the highest fresh and dry matter production, while those with 50% of the moisture content at field capacity and 50% of the fertilizer requirement recorded the least fresh and dry matter production. Yield was highest for plots with the water content kept at field capacity and 100% fertilizer application recording an average value of 22.87 ton/ha and least with plots with 50% of the moisture content at field capacity and 50% of the fertilizer treatment recorded 12.55 ton/ha. The study shows that moisture stress seriously affects grain amaranth than fertilizer stress. Also it shows that the fresh and dry matter accumulation and yield of grain amaranth depends on the on the soil moisture status.