Browsing by Author "Wortmann S. Charles"

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Low Input Approaches for Soil Fertility Management in Semiarid Eastern Uganda
(American Society of Agronomy, 2007) Kaizzi C. Kayuki; Byalebeka John; Wortmann S. Charles; Mamo Martha
Grain sorghum [Sorghum bicolor (L.) Moench] is an important food crop of semiarid sub-Saharan Africa. Crop yields are generally low, partly due to low soil fertility. Research was conducted with farmers to evaluate, soil fertility management practices in sorghum-based cropping systems including: mucuna [Mucuna pruriens (L.) DC.] fallow; cowpea [Vigna unguiculata (L.) Walp.] rotation with sorghum; animal manure application; N and P fertilizer application; and reduced tillage. Four studies, comprised of 142 on-farm trials, were conducted at three locations over 3 yr in drought-prone parts of eastern Uganda. Mucuna on average produced 7 Mg ha21 of aboveground dry matter containing 160 kg N ha21 across the three locations. Application of 2.5 Mg ha21 of manure and of 30 kg N plus 10 kg P ha21 increased grain yield by 1.05 and 1.30 Mg ha21, respectively. A combination of 2.5 Mg ha21 manure with 30 kg N ha21 increased grain yield by 1.50 Mg ha21 above the control (1.1 Mg ha21). The increase in sorghum grain yield in response to 30 kg N ha21 alone, to a mucuna fallow, and to a rotation with cowpea was 1.15, 1.55, and 0.82 Mg ha21, respectively. These soil fertility management practices, as well as reduced tillage, were found to be cost effective in increasing sorghum yield in the predominantly smallholder agriculture where inorganic fertilizer was not used much. On-farm profitability and food security for sorghum production systems can be improved by use of inorganic fertilizers, manure, mucuna fallow, sorghum–cowpea rotation, and reduced tillage. GRAIN SORGHUM is an important
Maize Response to Fertilizer and Nitrogen Use Efficiency in Uganda
(American Society of Agronomy, 2012) Kaizzi C. Kayuki; Byalebeka John; Semalulu Onesmus; Alou Isaac; Zimwanguyizza Williams; Nansamba Angella; Musinguzi Patrick; Ebanyat Peter; Hyuha Theodore; Wortmann S. Charles
Maize (Zea mays L.) is an important smallholder crop in Uganda. Yields are low because of low soil fertility and little fertilizer use. Yield response to nutrient application and economically optimal rates (EOxR, where x = N, P, or K) and N use effi ciency (NUE) were evaluated. Twenty-two trials were conducted in four agroecological zones. Yield was consistently increased with N application. Mean maize yield with no N applied (N0) was 1.79 Mg ha–1 and increased by 120% with N application. Mean EONRs were 45 to 24 kg ha–1 N with fertilizer use cost to grain price ratios (CPs) of 10 to 30. With N applied, the mean increase in yield due to P application was 0.28 Mg ha–1 and mean EOPRs were 9 to 1 kg ha–1 P with CPs of 10 to 50. Yield was not increased with K application. Profi tability was greater for N than P application. Mean aboveground biomass N with 0 and 150 kg ha–1 N applied was 46.3 and 94.3 kg ha–1, respectively. Mean N concentration and N harvest index at the EONR were 1.60 and 63.8%, respectively, and higher than for N0. Mean recovery effi ciency, partial factor productivity, and agronomic effi ciency declined with increasing N rate and were 66%, 86 kg kg–1, and 41 kg kg–1, respectively, at the EONR. Fertilizer N use can be very profi table, with high NUE, for smallholder maize production in Uganda, and the fi nancial capacity of smallholders to use fertilizer will increase with reduced CP
Sorghum Response to Fertilizer and Nitrogen Use Efficiency in Uganda
(American Society of Agronomy, 2012) Kaizzi C. Kayuki; Byalebeka John; Semaluluo Onesmus; Alou Isaac; Zimwanguyizza Williams; Nansamba Angella; Musinguzi Patrick; Ebanyat Peter; Hyuha Theodore; Wortmann S. Charles
Sorghum [Sorghum bicolor (L.) Moench] is important for smallholder production in semiarid parts of Uganda. Grain yields are low because of low soil fertility. Little fertilizer is used. Yield response to N, P, and K application, economically optimal rates for N, P, and K (EONR, EOPR, and EOKR, respectively), and N use effi ciency (NUE) were evaluated at 11 site-seasons. Mean sorghum yield with no N applied (N0) was 0.69 Mg ha–1 and was consistently increased by a mean of 230% with N application. Mean EONRs were 34 to 18 kg ha–1 N with fertilizer use cost to grain price ratios (CPs) of 10 to 30, respectively. Mean EOPRs were 11 to 2 kg ha–1 P with CPs of 10 to 50, respectively. Sorghum did not respond to K application. Net economic returns were greater for N than P application. Mean aboveground biomass N with 0 and 90 kg ha–1 N applied was 31.3 and 75.9 kg ha–1, respectively. Grain N concentration, N harvest index, and internal NUE at the EONR were 1.67%, 53.2%, and 31.8 kg kg–1, respectively, and higher than for N0. Mean recovery effi ciency, partial factor productivity, and agronomic effi ciency declined with increased N rate and were 135%, 79 kg kg–1, and 52 kg kg–1, respectively, at the EONR. Th e profi t potential of fertilizer N use is high for smallholder sorghum production in Uganda. Policy interventions to reduce fertilizer cost and improve grain marketing effi ciency will enable smallholders to increase fertilizer use for substantial increases in sorghum production.