Nitrogen balance and root behavior in four pigeonpea-based intercropping systems

A medium-duration pigeonpea (Cajanus cajan L. Millsp.) is usually grown as intercrop. A wide range of crop combination in pigeonpea-based intercropping systems is found in India and eastern Africa (Ofroi and Stern, 1987; Rao and Willey, 1980; Venkateswarlu and Subramanian, 1990). Although much information is available on the production efficiency and monetary advantage of intercropping, very little is known about the nitrogen (N) economy and root behavior. The study was carried out to examine how the nitrogen balance sheet and root development of pigeonpea could be altered by companion crops

Effects of Acacia seyal and biochar on soil properties and sorghum yield in agroforestry systems in South Sudan

We studied the effects of Acacia seyal Del. intercropping and biochar soil amendment on soil physico-chemical properties and sorghum (Sorghum bicolor L.) yields in a two-year field experiment conducted on a silt loam site near Renk in South Sudan. A split-plot design with three replications was used. The main factor was tree-cropping system (dense acacia + sorghum, scattered acacia + sorghum, and sole sorghum) and biochar (0 and 10 Mg ha(-1)) was the subplot factor. The two acacia systems had lower soil pH, N and higher C/N ratios compared to the sole sorghum system. Biochar significantly increased soil C, exchangeable K+ contents, field capacity and available water content, but reduced soil exchangeable Ca2+ and effective CEC, and had no effect on soil pH. Acacia intercropping significantly reduced sorghum grain yields while biochar had no significant effect on sorghum yields. The land equivalent ratio (LER) for sorghum yield was 0.3 for both acacia systems in 2011, with or without biochar, but increased in 2012 to 0.6 for the scattered acacia system when combined with biochar. The reduction in sorghum yields by the A. seyal trees was probably due to a combination of competition for water and nutrients and shading. The lack of a yield response to biochar maybe due to insufficient time or too low a dosage. Further research is needed to test for the effects of tree intercropping and biochar and their interactions on soil properties and crop yields in drylands.Peer reviewe

Ecological Considerations in the Selection of Leguminous Plants as Cover Crops on The Vertisols of the Accra Plains in Ghana

Experiments were conducted in 2003 and 2004 to select leguminous cover crops for the Accra plains ecology in Ghana, based on the ability to withstand drought, produce enough biomass and fix nitrogen. In a randomised complete block design, Crotalaria ochroleuca, Stylosanthes ha-mata, Stylosanthes guianensis, Aeschenomene histrix, Chamaecrista rotundifolia, Sesbania ses-ban and Leucena leucocephala were grown and plant residues incorporated into the soil. Other treatments were recommended inorganic fertilizer application and no fertilization (control). Maize was planted on all plots and data collected on biomass of leguminous residues and also shoot biomass, cob weight and grain yield of maize. Soil samples were taken and analysed for pH, organic carbon and nitrogen (N). The leguminous plant materials were also analysed for N, phosphorus (P) and potassium (K). Annual rainfalls of 2003 and 2004 were low and dry matter yields of some leguminous plants (e.g. Aeschenomene histrix and Chamaecrista rotundifolia) were consequently low. Also, Crotalaria ochroleuca, Leucena leucocephala, Sesbania sesban and Chamaecrista rotundifolia had higher percentage of N per unit dry weight than the other leguminous plants (3.1, 3.1, 2.8 and 2.8, respectively). In the major rainy season of 2004, maize after Sesbania sesban had higher total dry matter, cob weight and grain yield than observed in the unfertilized control and were comparable to those of the inorganic fertilizer application. Grain yields were 2.4, 0.9 and 3.5 t ha-1, respectively. In the minor season, crop growth and yield were much lower in all the treatments due to low rainfall. By virtue of its high vegetative growth and nitrogen fixation, Sesbania sesban was selected as suitable cover crop for the Accra plains

Utilization of Azolla as manure in lowland rice cultivation on the vertisols of the Accra plains of Ghana

On-farm studies were carried out in order to impart to farmers techniques of using azolla in lowland rice cultivation on the Vertisol. The experiments were conducted on four farms at the Kpong Irrigation Project sites, at Akuse and Asutsuare, from 2002 to 2006. The design of experiment was randomised complete block, with five treatments and four replications. Azolla was grown in designated rice basins (3m x 4 m) for 6 weeks and water drained three days before transplanting rice. Azolla was also grown in external basins and added to give total of 25 t ha-1 fresh weight (1.2 t ha-1 dry weight). As rice was transplanted, azolla was trampled and thus incorporated into the soil. The treatments included: Incorporated azolla only (A1), azolla + 15:15:15 NPK compound fertilizer application (A2), azolla + 15:15:15 NPK fertilizer + ½ sulphate of ammonia fertilizer (A3), application of recommended 15:15:15 NPK fertilizer + sulphate of ammonia (F) and no azolla or inorganic fertilizer application - control (N). Data on the rice crop included: plant height, tillers per plant, total dry weight at booting stage and grain yield at maturity. Soils were sampled at the end of experiments and analysed for pH, nitrogen and organic carbon. The nitrogen content of incorporated azolla was 2.2 %, giving a nitrogen equiva-lent of 27 kg ha-1. Azolla plus 15:15:15 NPK fertilizer gave a yield of 5.3 t ha-1 paddy (A2) that was comparable to that of the recommended inorganic fertilizer applications (F) - 5.1 t ha-1 and greater than the control (N) - 2.9 t ha-1. In Hammond’s farm, where azolla was incorporated over a period of three years, rice yield was higher than observed in Moses’ farm, where azolla incorporation was for one year only. Cost-benefit analysis indicated a 20.7 % savings on fertilizer application

Genomic heterogeneity within cowpea bradyrhizobia isolated from Ghanaian soils

No Abstract