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.

Journal articleIFPRI3EPTDP

Peanut (Arachis hypogaea L.) yield and financial returns are often low for smallholder farmers in Ghana.  Additionally, aflatoxin concentration in foods derived from peanut can be high enough to adversely affect human health.  Eight experiments were conducted in 2016 and 2017 in northern Ghana to compare yield, financial returns, pest reaction, and aflatoxin contamination at harvest with traditional farmer versus improved practices.  Relative to the farmer practice, the improved practice consisted of weeding one extra time, applying local potassium-based soaps to suppress arthropods and pathogens, and application of either homogenized oyster shells or a commercial blend of fertilizer containing calcium.  Each of these field treatments were followed by either drying peanut on the soil surface and storing in traditional poly bags or drying peanut on tarps and storing in hermetically-sealed bags for 4 months.  Peanut yield and financial returns were significantly greater when a commercial blend of fertilizer or oyster shells were applied compared to the farmer practice of not applying any fertilizer.  Yield and financial returns were greater when a commercial fertilizer blend was applied compared with oyster shells.  Severity of early leaf spot [caused by <em>Passalora arachidicola</em> (Hori) U. Braun] and late leaf spot [caused by <em>Nothopassalora personata</em> (Berk. & M.A. Curtis) U. Braun, C. Nakash., Videira & Crous], scarring and penetration of pods by arthropods, and the number of arthropods at harvest were higher for the farmer practice than for either fertility treatment; no difference was noted when comparing across fertility treatments.  Less aflatoxin was observed for both improved practices in the field compared with the farmer practice.  Drying peanut on tarps resulted in less aflatoxin compared to drying peanut on the ground regardless of treatments in the field.  Aflatoxin concentration after storage was similar when comparing post-harvest treatments of drying on soil surface and storing in poly bags vs. drying on tarps and storing in hermetically-sealed bags. These results demonstrate that substantial financial gain can be realized when management in the field is increased compared with the traditional farmer practice.

A gronomy J our n al • Volume 10 8 , I ssue 1 • 2 016 1 G rain sorghum is one of the most drought-and stresstolerant crops grown in the world, especially in semiarid regions. For this reason, much of the world's grain sorghum is grown in high-risk environments where other crops are more likely to fail or be unprofi table. Although grain sorghum uses N effi ciently, either equal to or better than C 3 cereals, N defi ciency suppresses plant growth and dry matter accumulation (Zhao et al., 2005). Leguminous cover crops have been envisaged as a critical component of sustainable cropping systems because of their potential to increase soil productivity through cycling of C, N, and other nutrients (including P) in agricultural systems (Chikowo et al., 2004) and have been used to improve environmental quality by reducing soil erosion and nutrient losses through surface runoff . Th e use of winter cover crops has been emphasized (Clark et al., 1995). Blackshaw et al. (2001) measured a 16 to 52 kg ha -1 increase in soil N following a sweetclover [Melilotus offi cinalis (L.) Pall.] cover crop compared with fallow treatments and wheat (Triticum aestivum L.) yields were 47 to 75% greater following sweetclover rather than fallow treatments, suggesting enhanced N availability from the legume residue.Little information is available on the contribution of summer cover crops to succeeding cereal crop production under a no-till (NT) system. Agricultural management systems that involve soil management practices such as NT have the potential to generate both economic and environmental benefi ts, including mitigating soil erosion, reducing energy use and C emissions, enhancing the timeliness of planting, and saving labor and time (West and Marland, 2002). No-till sequesters C in the soil, thereby mitigating the negative impact of climate change (West and Marland, 2002). Th e improvements generated by the adoption of NT techniques oft en have positive eff ects on crop growth and yield. Studies have shown that the eff ects of NT on crop productivity can vary with other crop management practices and that NT generally produces a better result when combined with a well-planned crop rotation (Amato et al., 2013).Previous research has demonstrated that leguminous cover crops can decrease inorganic N fertilizer requirements and production costs through symbiotic N 2 fi xation (Cherr et , double-cropped soybean, and double-cropped grain sorghum in the rotation compared with a fallow system with 0 kg N ha -1 were 56, 62, 43, 32, and 3%, respectively, and NFRVs across the years were 53, 64, 36, 27, and -3 kg N ha -1 , respectively. Across years, grain sorghum in a double-cropped soybean system and a fallow system with 90 kg N ha -1 gave profi table economic net returns. We conclude that including leguminous cover crops in a cropping system has the potential to reduce N requirements and improve the N availability and grain yield of the succeeding grain sorghum crop.

Nitrous oxide (N2O) emission from denitrification in agricultural soils often increases with nitrogen (N) fertilizer and soil nitrate (NO3−) concentrations. Our hypothesis is that legume cover crops can improve efficiency of N fertilizer and can decrease N2O emissions compared to non–cover crop systems. The objectives of this study were to (a) evaluate the performance of summer leguminous cover crops in terms of N uptake and carbon (C) accumulation following winter wheat and (b) to quantify the effects of summer leguminous cover crops and N fertilizer rates on N2O emissions and grain yield of the subsequent grain sorghum crop. Field experiments were conducted in the context of a wheat-sorghum rotation for two seasons in Kansas. Treatments consisted of double-cropped leguminous cover crops following winter wheat harvest with no fertilizer applied to the following grain sorghum or no cover crop after wheat harvest and N fertilizer rates applied to the grain sorghum. The cover crops were cowpea (Vigna unguiculata L. Walp.), pigeon pea (Cajanus cajan L. Millsp.), and sunn hemp (Crotalaria juncea L.). The three N treatments (were 0, 90, and 180 kg·N·ha−1). Fallow systems with 90 and 180 kg·N·ha−1 produced significantly greater N2O emissions compared with cropping systems that received no N fertilizer. Emissions of N2O were similar for various cover crops and fallow systems with 0 kg·N·ha−1. Among cover crops, pigeon pea and cowpea had greater C accumulation and N uptake than sunn hemp. Grain yield of sorghum following different cover crops was similar and significantly higher than fallow systems with 0 kg·N·ha−1. Although fallow systems with 90 and 180 kg·N·ha−1 produced maximum sorghum grain yields, N2O emissions per unit of grain yield decreased as the amount of N fertilizer was reduced. We conclude that including leguminous cover crops can decrease N fertilizer requirements for a subsequent sorghum crop, potentially reducing N2O emissions per unit grain yield and providing options for adaptation to and mitigation of climate change.