Relative efficacy of cocoa pod husk-based compost on growth and nutrient uptake of cocoa seedlings in the nursery

The effect of cocoa pod husk-based compost on growth and nutrient uptake of cocoa seedlings was compared with conventional NPK 15-15-15 fertilizer at the nursery in a randomized complete block design experiment. Poly bags were filled with either top soil or compost alone, and also with mixtures of top soil, compost and inorganic fertilizer in various ratios to provide the following treatments: soil alone, compost alone, 1 : 1 soil/compost, soil + fertilizer, 1 : 1 soil/compost + fertilizer, 1 : 2 soil/compost, 1 : 2 soil/compost + fertilizer, 2 : 1 soil/compost, 2 : 1 soil/compost + fertilizer. The fertilizer was added at the rate of 6 g per poly bag. Plant height, girth, leaf area, dry matter yield, and root volume of cocoa seedlings were significantly (P<0.05) affected by the potting media at 24 weeks after sowing. Potting media with the fertilizer additions significantly (P<0.05) produced shorter seedlings with smaller stems and narrower leaves. Root volumes and total dry matter yield of seedlings positively correlated (r = 0.733), and were significantly (P<0.05) higher in soil/compost mixtures than in treatments with fertilizer additions. Irrespective of the potting media, the uptake of N by the seedlings was higher than P and K. However, the addition of fertilizer to the potting media with compost resulted in lower N uptake by the seedlings. The use of compost developed from cocoa pod husk as potting medium or soil amendment for nursing cocoa seedlings enhanced better seedling growth than when used in combination with NPK 15-15-15 fertilizer

Impact of shade and cocoa plant densities on soil organic carbon sequestration rates in a cocoa growing soil of Ghana

Cropping systems have influence on the conservation of soil organic matter. Soil samples were taken from a long term experiment that was designed to study the impact of shade and cocoa plant densities on cocoa yields. The impact of the treatments on soil organic carbon sequestration rates and the gains or losses of soil organic carbon under the treatments with reference to adjacent undisturbed bush were assessed. The experiment was sited at the Bunso substation of the Cocoa Research Institute of Ghana on Rhodi-lixic ferralsol with annual precipitation of about 1500 mm. The shade was provided by forest trees of 18 trees ha-1 and no shade, while the cocoa densities were 1111, 1428 and 1667 trees ha-1. Shade effects on organic carbon pools within the top soil (0-30 cm) under cocoa were not significant (p=0.05). Cocoa plant densities per unit area influenced the soil organic carbon pools. The soil organic carbon pools were significantly lower (p=0.05) in the closely planted farms than in the widely spaced farms. There were no soil organic carbon sequestration in the highest cocoa plant density of 1667 trees ha-1 but 250 and 190 kg soil organic carbon ha-1 yr-1 in the top soil (0-15 cm) were sequestered in the soils under cocoa with density of 1111 trees ha-1 for shaded and unshaded farms respectively. Irrespective of the shade conditions, the net gains of carbon in the soils were higher in farms with lower cocoa plant density. The results suggest that cocoa planted at low plant density under shade stores more carbon per unit area of soil than an equivalent area of cocoa planted at high density without shade. It is concluded that cocoa farming could be an effective means to mitigate carbon dioxide emissions in cocoa growing countries.Key words: Soil organic carbon, sequestration rates, cocoa plant density, shade

The Economics of Agricultural R&D

Agricultural research has transformed agriculture and in doing so contributed to the transformation of economies. Economic issues arise because agricultural research is subject to various market failures, because the resulting innovations and technological changes have important economic consequences for net income and its distribution, and because the consequences are difficult to discern and attribute. Economists have developed models and measures of the economic consequences of agricultural R&D and related policies in contributions that relate to a very broad literature ranging across production economics, development economics, industrial organization, economic history, welfare economics, political economy, econometrics, and so on. A key general finding is that the social rate of return to investments in agricultural R&D has been generally high. Specific findings differ depending on methods and modeling assumptions, particularly assumptions concerning the research lag distribution, the nature of the research-induced technological change, and the nature of the markets for the affected commodities