Nutrient Management Options For Enhancing Sesame (Sesamum Indicum L.) Seed Yield And Nutritional Quality In North Eastern Uganda

Abstract

Sesame (Sesamum indicum L.) production in north eastern Uganda is constrained by low soil fertility. Incorporation of crop residues and fertilizer in soil has a potential to enhance soil fertility and productivity of sesame; however, there is limited information on the effect of crop residues and fertilizers on the agronomic performance and nutritional quality of sesame. A study was conducted at the National Semi-Arid Resources Research Institute (NaSARRI), Serere, Uganda with the following objectives: (1) to determine the chemical composition and nutrient release rates and patterns of selected crop residues; (2) to determine the effect of selected crop residues and animal manure on soil bulk density, soil moisture content and sesame water use efficiency; (3) to evaluate the effects of selected crop residues and animal manure on nutrient uptake, growth, yield and nutritional seed quality of sesame; and (4) to determine the effects of selected crop residues and NPK fertilizer on growth, yield and nutritional seed quality of sesame. Field and screen house experiments were conducted in the short rains of 2013 and 2014, and 2014 long rains. In objective 1, groundnut shells and husks of finger millet, sorghum and cowpea were evaluated for their decomposition rates, nutrient content and nutrient release rates. In objectives 2 and 3, the four crop residues, poultry manure, cattle manure, poultry manure plus each of the four crop residues and cattle manure plus each of the four crop residues were evaluated for their effects on the soil properties and sesame yield. In objective 4, millet husks, sorghum husks, cowpea husks and groundnut shells each at 3 and 6 t/ha, 30 kg N-25 kg P-40 kg K /ha, 60 kg N-50 kg P-80 kg K /ha, 30 kg N-25 kg P-40 kg K /ha plus each of the four crop residues at 3 and 6 t/ha and 60 kg N-50 kg P-80 kg K/ha plus each of the four crop residues at 3 and 6 t/ha were evaluated for their effect on sesame yield. All the experiments had a control treatment (no external amendments). The design used for all the experiments was randomized complete block design. In objective 1, nutrient content, nutrient release rates and dry matter disappearance rates of crop residues were determined. In objective 2, soil bulk density, soil moisture content and sesame water use efficiency were determined. In objective 3 and 4, nutrient uptake, plant height, number of branches per plant, leaf area index, number of capsules per plant, harvest index, biological yield, straw yield, seed weight per plant, thousand seed weight, seed yield, crude protein content, total ash content and oil content were determined. Finger millet husks had significantly higher initial C (36.28 %) and N (3.46 %) contents and lower C/N ratio xvii (10.45) than other crop residue treatments. Under incubation, finger millet husks had significantly higher dry matter mean disappearance rate (0.0447 % week-1) and N mean release rate (0.0558 % week-1) than other crop residues; whereas groundnut shells and sorghum husks had significantly lower mean dry matter disappearance rate (0.0009 % week-1) and mean N release rate (0.0223 % week-1) respectively than other crop residues. Crop residue nutrient release and disappearance rates occurred in the order: finger millet husks>cowpea husks>sorghum husks>groundnut shells. Plots treated with 6 t/ha of poultry manure plus finger millet husks had higher soil moisture content (33.01 to 38.09 %) and lower soil bulk density (1.68 to 1.05 kg/cm3) than the control and all other treatments; while plots amended with 3 t/ha of poultry manure plus finger millet husks produced higher sesame water use efficiency (7.91 to 9.92 kg ha-1mm-1) than the control and all other treatments. Plots treated with 6 t/ha of poultry manure plus finger millet husks produced significantly taller plants (126.7 to 147.3 cm) and higher number of branches (4.41 to 4.80), leaf area indices (4.48 to 5.73), biological yield (9.8 to 20.7 t/ha), straw yield (7.2 to 11.8 t/ha), crude protein (26.35 to 46.23 %) and leaf N (3.61 to 4.84 %), P (0.26 to 0.66 %) and K (0.19 to 1.86 %) content than the control and other treatments. Crop residue enhancement of seed crude protein content followed the order: finger millet husks>cowpea husks>groundnut shells>sorghum husks. In contrast, plots amended with 3 t/ha of poultry manure plus finger millet husks had higher number of capsules per plant (38.5 to 79.9), harvest indices (0.41 to 0.75) and seed yield (0.55 to 1.33 t/ha) than the control and all other treatments. Application of 6 t/ha of cowpea husks plus poultry manure produced the highest seed total ash content (4.57 to 8.71 %), while 6 t/ha of groundnut shells produced the highest seed oil content (59.80 to 69.29 %) compared to the control and all other treatments. Crop residue enhancement of sesame seed yield and seed total ash were in the order: finger millet>cowpea>sorghum>groundnut. In contrast, crop residue enhancement of seed oil content followed the order: groundnut>sorghum>cowpea>finger millet. Application of 6 t/ha of finger millet husks plus 60 kg N-50 kg P-80 kg K /ha significantly increased plant height (137.5 to 182.5 cm), number of branches per plant (4.75 to 7.99), biological yield (9 to 22.1 t/ha) and straw yield (6 to 21.7 t/ha) compared to the control, sole crop residues and inorganic fertilizer regimes. Sesame plants harvested from plots treated with 3 t/ha of finger millet husks plus 30 kg N-25 kg P-40 kg K /ha produced significantly higher seed yield (0.5 xviii to 1.94 t/ha) than the control, individual crop residues and inorganic fertilizer regimes. Finger millet husks had a lower C/N ratio and a higher nutrient release rate than sorghum husks, cowpea husks and groundnut shells. Finger millet husks were more effective in increasing seed yields and nutritional quality of sesame than other crop residues; whereas poultry manure plus finger millet husks was more effective in improving growth, nutrient uptake and crude protein content of sesame, soil moisture content and soil bulk density, water use efficiency and seed yield of sesame than crop residues or animal manure alone. Finger millet husks (3 t/ha) combined with 30 kg N-25 kg P-40 kg K /ha enhanced seed yield and oil content of sesame