Abstract
Low soil fertility, pests and diseases are major problems of growth and establishment of cacao seedlings on the field. Cocoa production increases by new plantings and rehabilitation of moribund farms, but a build-up of plant-parasitic nematodes (PPN) causing dieback and declining soil fertility has discouraged many farmers, leading to a reduction in crop productivity. In this study, the potentials of some organic wastes as fertilizers and their effects on establishment of cacao seedlings in PPN infected soils was investigated at Ibadan and Owena of Southwestern Nigeria. Goat dung (GD), organic fertilizer (OF), organo-mineral fertilizers (OMF) and NPK 15:15:15 were applied at 200, 400 and 600 kg ha-1, respectively, to cacao seedlings one month after transplanting, while unfertilized served as control. Results from the experiments showed a significant increase in percentage survival of cacao seedlings under organic fertilizers at Ibadan and Owena compared to NPK and control even at the lowest rate of 200 kg ha-1 3 years after transplanting. The incorporation of GD, OF and OMF significantly reduced the population densities of PPN compared to control. Therefore, GD, OF and OMF at 200 kg ha-1 are recommended for soil application to enhance the field establishment of cacao seedlings in the soil infected with PPN.
Highlights
Cocoa (Theobroma cacao L.) is cultivated in the humid tropics of the world (Yanelis et al, 2012) with more than 70 % production coming from Africa as a source of income for producing countries (Simo et al, 2018)
Cocoa production increases through new plantings and rehabilitation of moribund farms, but the build-up of plant-parasitic nematodes causing die-back of cacao seedlings in nurseries and young plantations and declining soil fertility caused many farmers to be discouraged leading to a reduction in crop productivity (Orisajo et al, 2012; Orisajo, 2018)
The experiment was set as a randomized complete block design involving four fertilizer types: goat dung (GD), organic (OF), organo-mineral fertilizer (OMF) and NPK 15:15:15, which were separately applied at 200, 400, 600kg ha-1 and unfertilized served as control
Summary
Cocoa (Theobroma cacao L.) is cultivated in the humid tropics of the world (Yanelis et al, 2012) with more than 70 % production coming from Africa as a source of income for producing countries (Simo et al, 2018). Cocoa production has witnessed a downward trend due to declining soil fertility, pests and diseases, aging trees and low yields from smallholder farms. Low farm gate prices paid to farmers make it difficult for them to afford expensive inputs to increase soil fertility and yield, such as mineral fertilizers, and pesticides to control pests and diseases adverse effects. Cocoa production increases through new plantings and rehabilitation of moribund farms, but the build-up of plant-parasitic nematodes causing die-back of cacao seedlings in nurseries and young plantations and declining soil fertility caused many farmers to be discouraged leading to a reduction in crop productivity (Orisajo et al, 2012; Orisajo, 2018). The need to pay attention to soil fertilization is almost as important as the control of pests and diseases in cocoa. Tropical soils are inherently low in soil organic matter and fertility status; external fertilizer supply is a key factor in raising crop production
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