Conservation agriculture (CA) practices are being widely promoted in many areas in sub-Saharan Africa to recuperate degraded soils and improve ecosystem services. This study examined the effects of three tillage practices [conventional moldboard plowing (CT), hand hoeing (MT) and no-tillage (NT)], and three cropping systems (continuous maize, soybean–maize annual rotation, and soybean/maize intercropping) on soil quality, crop productivity, and profitability in researcher and farmer managed on-farm trials from 2010 to 2013 in northwestern Ghana. In the researcher managed mother trial, the CA practices of NT, residue retention and crop rotation/intercropping maintained higher soil organic carbon, and total soil N compared to conventional tillage practices after 4 years. Soil bulk density was higher under NT than under CT soils in the researcher managed mother trails or farmers managed baby trials after 4 years. In the researcher managed mother trial, there was no significant difference between tillage systems or cropping systems in maize or soybean yields in the first three seasons. In the fourth season, crop rotation had the greatest impact on maize yields with CT maize following soybean increasing yields by 41 and 49% compared to MT and NT maize, respectively. In the farmers’ managed trials, maize yield ranged from 520 to 2700 kg ha-1 and 300 to 2000 kg ha-1 for CT and NT, respectively, reflecting differences in experience of farmers with NT. Averaged across farmers, CT cropping systems increased maize and soybean yield ranging from 23 to 39% compared with NT cropping systems. Partial budget analysis showed that the cost of producing maize or soybean is 20–29% cheaper with NT systems and gives higher returns to labor compared to CT practice. Benefit-to-cost ratios also show that NT cropping systems are more profitable than CT systems. We conclude that with time, implementation of CA practices involving NT, crop rotation, intercropping of maize and soybean along with crop residue retention presents a win–win scenario due to improved crop yield, increased economic return, and trends of increasing soil fertility. The biggest challenge, however, remains with producing enough biomass and retaining same on the field.

Grain sorghum [Sorghum bicolor (L.) Moench] is an important crop in semiarid regions of the world because of its drought tolerance. Nitrogen is one of the most limiting nutrients in crop production due to low availability and loss. We hypothesize that there are di erences in physiological and yield traits among grain sorghum genotypes in response to N. e objectives of this study were to determine the responses of sorghum genotypes (hybrids and inbred lines) to N fertilizer and the relationship between their physiological and yield traits. Field experiments were conducted at two locations in Kansas for two seasons (2010 and 2011). Genotype × N regimes and year × genotype interactions were signi cant for leaf chlorophyll, aboveground biomass, grain yield, and seed number. Overall, the hybrids were superior to inbred lines for grain yield and total aboveground biomass, but grain yields of inbred lines TX2783 and TX7000 were comparable to hybrids. Maximum total aboveground biomass, leaf chlorophyll index, and grain yield were obtained at 90 kg N ha -1 . Across years, application of 45 and 90 kg N ha -1 resulted in an increase in yield of 13 and 48% over 0 kg N ha -1 , respectively. No strong relationship was detected between genotypes and leaf chlorophyll index or chlorophyll a uorescence and grain yield, but there was a strong relationship between seed number and total aboveground biomass and grain yield. Leaf chlorophyll index and chlorophyll a uorescence did not provide physiological basis for di erences in N response among the genotypes for grain yield.

Leguminous cover crops are considered part of sustainable agricultural systems. With the development of no-till cropping systems, cover crops have been recognized for their ability to provide N for succeeding crops. Th e objectives of this study were: (i) to determine the N contribution of summer cover crops and double-cropped grain crops following winter wheat (Triticum aestivum L.) and N rates to subsequent maize (Zea mays L.) crops' physiological traits and yield, (ii) to calculate the fertilizer N replacement value, and (iii) to perform economic analyses of the cropping systems. in the rotation over the fallow system with 0 kg N ha -1 was 78, 91, 66, 72, and 12%, respectively. Fertilizer N replacement values for cowpea, pigeonpea, sunn hemp, double-cropped soybean, and double-cropped grain sorghum were 53, 64, 43, 47, and -5 kg N ha -1 , respectively. We conclude that the inclusion of summer leguminous cover crops in a cropping system has the potential to reduce or supplement N requirements and increase the grain yield of subsequent maize crops.

Prior on-station research showed that sowing dates, sowing density and applications of fungicide and phosphorus (P) increased groundnut (Arachis hypogaea) pod yield by 60-80%. Farmer-managed trials were conducted in the Wa district of the Upper West Region of Ghana from 2004 to 2007 to test the yield response to sowing density, fungicide and P and to assess economic returns of these technologies to farmers. Treatments included: an early maturing groundnut cultivar, Chinese, sown at farmers' density (5-8 plant m −2 ) without fungicide and without P application (T1, control), with fungicide sprays alone (T2), or with fungicide and P application (T3), cultivar Chinese sown at recommended (higher) density (20 plant m −2 ) with fungicide and P application (T4), and a full season cultivar, Manipinter, with fungicide and P application (T5). Soil fertility, sowing density, days from sowing to first weeding, incidence and severity of leaf-spot disease and plant population at final harvest were recorded. Relative to farmers' practice, pod yield of cultivar Chinese was significantly increased by 80% with fungicide sprays alone, 108% with fungicide and P application, and 113% with fungicide and P application at higher sowing density. Cultivar Manipinter treated with fungicide and P gave 107% increase in pod yield relative to farmers' practice. Correlation and stepwise regression analyses suggested that major determinants of groundnut pod yield in farmers' fields were plant density, leaf-spot disease and P availability. The increase in yield with fungicide and P application translated into a 4-5-fold increase in gross margin for farmers in the region. Returns to labour and labour productivity were doubled with combined use of fungicide and P fertilizer.

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