Poor soil fertility remains the major cause of low crop productivity on smallholder farms that are engaging in vegetable production in sub-Saharan Africa. Appropriate soil fertility regimes are therefore critical for improving crop productivity. Its yield has remained low mainly due to poor soil fertility. A field experiment in two different seasons was planted in a Completely Randomized Block Design using Solanum aethiopicum Shum (Nakati). The treatments were 3 sole fertilizer options applied at the following rates: poultry manure and bio-slurry manure at 5, 10, 15, 20, 25 and 30 t ha-1, NPK (25:5:5) at the recommend application rate for tomato which is a sister crop and a control without any fertilizer. Crop budgets were used to determine the economic optimum rates of both sole applications of manure and combinations of manure with NPK. The sole applications and showed significantly (p ≤ 0.05) increased the yield of S. aethiopicum compared with the control. The established biological optimum rates were at 24.19 t ha-1 and 21.51 t ha-1 for poultry manure and bio-slurry respectively. Using the crop budgets it was concluded that the established economic optimum rates were 20 t ha-1 and 10 t ha-1 for sole poultry manure and bio-slurry respectively. Recommendations for use of sole poultry manure and bio- slurry at the rate of 20 t ha-1 and 10 t ha-1 respectively were made.

Most of the important sweetpotato (Ipomoea batatas (L.) Lam) traits are sensitive to environmental change. This necessitates evaluating new sweetpotato genotypes in different environments to identify those that are stable. To enhance adoption, the new sweetpotato genotypes should have farmer preferred traits thus the need for farmer involvement during selection. This study was conducted to: evaluate and select promising sweetpotato F1 genotypes with wide and specific adaptation, in association with performance for farmer preferred traits. Twenty-one promising sweetpotato F1 genotypes were evaluated at Namulonge, Serere and Kachwekano with Tanzania and NASPOT 1 as checks. The randomised complete block design with three replications was used. Scientists and farmers evaluated the agronomic performance and quality traits of the genotypes before and at harvest. Significantly (P<0.05) higher mean total storage root yield (TRY) of 25.5 t ha -1 was recorded at Namulonge than at Kachwekano and Serere. Genotypes G67, G13, G14, G24 and G29 were the most stable across the sites for TRY and therefore the most widely adapted for this trait, while G68, G60 and G58 were specifically adapted to Kachwekano and Serere. Very low severity levels of Sweetpotato virus disease (SPVD) were recorded with a mean score of 1.9 across sites with Namulonge having the highest mean score of 2.3. Genotypes G14, G16, G24, G29 and G49 were the most stable across the sites for low Alternaria blight severity and can therefore, be recommended for cultivation in both low and high disease pressure areas. In the participatory selection, before harvest and at harvest, Spearman's rank correlation (r = 0.44) of the scientists and farmers' mean ranking of the genotypes at each site was positive and significant. Thus scientists were capable of selecting for farmer preferred traits. In addition, the study identified and selected five superior genotypes including G13, G14, G24, G49 and G69 for further evaluation.

Alternaria leaf petiole and stem blight (Alternaria spp.) is an important sweetpotato (Ipomoea batatas (L.) Lam.) disease in Uganda. Severity of the disease varies with environment, with higher disease levels recorded under high moisture and humidity conditions. To breed for resistance to this disease, germplasm that is resistant must be identified through multi-locational trials. This study was conducted to evaluate selected sweetpotato genotypes for stable resistance to Alternaria blight across sites and seasons. Thirty sweetpotato genotypes from different agro-ecological zones of Uganda and the National Sweetpotato Program were evaluated for resistance to Alternaria blight using fungicide treatment and Alternaria blight pathogen inoculation at Namulonge and Kachwekano over three seasons. There were highly significant differences among the genotypes for Alternaria blight severity with higher disease levels at Kachwekano than Namulonge. Genotypes Shock, Silk Luwero and the resistant check Tanzania had the lowest Alternaria severity and were therefore the most resistant while NASPOT 1 and NASPOT 7 had the highest severity values and were the most susceptible. Improved cultivars were more susceptible than the landraces. Genotypes Tanzania and Namusoga and environment Namulonge 2015B were the most stable for Alternaria blight. Treatment with fungicide resulted in variable reductions in Alternaria blight severity among genotypes across seasons and sites with NASPOT 1 having the lowest percentage reduction of 40.8% between the Alternaria inoculated and fungicide treated plots. Kigaire recorded the highest percentage disease reduction of 63.6%. Those genotypes with acceptable performance for Alternaria blight may be used as parents in breeding new genotypes with improved performance.