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 efficiency (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. Profitability 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 efficiency, partial factor productivity, and agronomic efficiency 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 profitable, with high NUE, for smallholder maize production in Uganda, and the financial capacity of smallholders to use fertilizer will increase with reduced CP.

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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 efficiency (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 efficiency, partial factor productivity, and agronomic efficiency declined with increased N rate and were 135%, 79 kg kg−1, and 52 kg kg−1, respectively, at the EONR. The profit potential of fertilizer N use is high for smallholder sorghum production in Uganda. Policy interventions to reduce fertilizer cost and improve grain marketing efficiency will enable smallholders to increase fertilizer use for substantial increases in sorghum production.

This research investigated empirically the qualities of improved soil management practices (ISMPs) most likely to lead to land user adoption. Land users' perceptions of soil‐related constraints were investigated in two hillside districts of eastern Uganda. The research looked at land user rationale for adopting and adapting specific ISMPs at the end of a two‐year period of increased advice and support. Land user engagement with soil management improved markedly after this period of support and multifunctionality, that is, provision of a number of different products or benefits, was seen to be a common characteristic of those ISMPs taken up by land users. It is argued that in the search for ‘best‐bet’ ISMPs, multifunctionality may be a particularly relevant and easily measurable indicator of likely adoption of a practice by land users. The research also demonstrates the value of supporting land users in their efforts to adapt ISMPs to fit with their own circumstances. Copyright © 2011 John Wiley & Sons, Ltd.

Application of iron (Fe) -rich amendments to soils has been proposed as a means of decreasing phosphorus (P) losses from soils. However, anoxic conditions following soil saturation are known to increase Fe and P solubility in soils, thus cancelling out the potential benefits. Our aim was to evaluate the effects of continuous oxic, continuous anoxic and alternating anoxic/oxic conditions on P exchangeability and Fe forms in soil amended with Ca(OH) 2 and FeSO 4 . We incubated amended and unamended soils under these conditions for 8 weeks and measured Fe forms and P exchangeability. Under oxic conditions, addition of Ca(OH) 2 and FeSO 4 resulted in a strong decrease in P exchangeability and an increase in oxalate-extractable Fe. Mo¨ssbauer analyses suggested that an unidentified Fe oxide (D1oxide) with a strong sorbing capacity for P was precipitated. Under continuously anoxic conditions, P exchangeability and oxalate-extractable Fe increased with or without the amendments. Mo¨ssbauer analyses suggested that there was a partial dissolution of the D1oxide phase, precipitation of another unidentified Fe oxide (S3) and a reduction of structural Fe 3þ in phyllosilicate, thereby increasing soil negative charge. These transformations resulted in a strong increase in rapidly exchangeable P. Alternating anoxic and oxic periods induced the dissolution and precipitation of iron oxides and the increase and decrease in P exchangeability. Implications of the results for limiting P losses from grassland soils are discussed.

Access to information and new technologies avails smallholder farmers an opportunity to improve their production decisions. However, access to information on technologies per se may not be relevant if the technologies are not adopted. This study was aimed at determining the factors that enable participants to access information on integrated soil fertility management (ISFM) technologies and to apply these technologies in groundnut production. It was conducted in the major groundnut producing districts of Tororo, Mbale, and Bukedea; where 155 Producers were surveyed. Probit and Multinomial Logit (MNL) models were fitted to the data using STATA analytical package. The results reveal that on average, producers in production groups were more likely to access information and to use new groundnut production technologies compared to their counterparts without groups. In addition, group membership, sex of farmer, and education also pre-disposed producers and processors to access and use new groundnut technologies. Smallholder farmers should be encouraged to form and work in groups as they facilitate knowledge sharing and technology adoption.

Common bean (Phaseolus vulgarisL

Abstract. A field study was conducted with the following objectives in mind: I) to study the effect of soil addition to weathered fly ash on the establishment and survival of different grasses and legumes, 2) to identify suitable grasses and/or legume species for vegetation of fly ash, 3) to study the fertilizer N and P requirements for successful vegetation establishment on fly ash and ash-soil mixtures, 4) to examine the nutrient composition of the plant species tested, and 5) to study the plant availability of P from fly ash and ash-soil mixtures. Three rooting media were used: weathered fly ash, and 33% or 50% soil blended with the ash. Four experiments were established on each of these media to evaluate warm season grasses in pure stands, warm season grasses inter-seeded with legumes, cool season grasses, and cool season grasses inter-seeded with legumes. Soil used in this study was more acidic than the fly ash. Only the results from characterization of the rooting media, ground cover, and yield will be presented here. Additional