African Journal of Tropical Agriculture

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (11), pp. 001-004, November, 2016. © International Scholars Journals

Full Length Research Paper

Management of black pod disease of cocoa with reduced number of fungicide application and crop sanitation

I. Y. Opoku, M. K. Assuah and F. Aneani

Cocoa Research Institute of Ghana, P. O. Box 8 Tafo, Akim, Ghana.

Accepted 18 July, 2016

Abstract

Black pod disease caused by Phytophthora megakarya is the most important fungal disease on cocoa in Ghana. The current recommended control method of combining sanitation practices with 6 - 8 fungicide applications in a year is considered unfriendly to the environment, too expensive and time consuming. Consequently, fungicide adoption rate by farmers is extremely low. Studies were therefore conducted to determine the effectiveness of combining 1 - 3 fungicide application in June and/or September/October with crop sanitation for the control of cocoa black pod disease caused by P. megakarya. Sanitation practices were common to all the treatments and the fungicide application(s) superimposed. A semi-systemic fungicide, Ridomil 72 plus (12% metalaxyl + 60% copper-1-oxide), was used as the test fungicide. Fungicide application combined with crop sanitation practices were effective in the management of the severe form of black pod disease caused by P. megakarya, resulting in 25% to 48% disease reduction and 10.9% to 51.8% yield increase. Combining the sanitation practices with three fungicide applications gave significantly better results, in terms of disease control and yields than either sanitation practices alone or combining them with one or two fungicide applications. However, the combination of sanitation practices and three fungicide applications was significantly less effective than the standard fungicide application of six times a year. All the fungicide applications and/or crop sanitation practices were profitable with a Benefit Cost Ratio (BCR) ranging from 1.8 - 2.1.

Keywords: Cocoa, fungicides, sanitation practices, black pod, benefit cost ratio, Phytophthora megakarya.

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (10), pp. 001-007, October, 2016. © International Scholars Journals

Full Length Research Paper

The challenges of rehabilitating denuded patches of a semi-arid environment in Kenya

Kevin Z. Mganga¹*, Moses M. Nyangito¹, Nashon K. R. Musimba¹, Dickson M. Nyariki¹, Agnes

W.  Mwangombe², Wellington N. Ekaya³, William M. Muiru², Daniele Clavel⁴, Judith Francis⁵, Ralph von Kaufmann ⁶ and Jan Verhagen⁷

¹Department of Land Resource Management and Agricultural Technology University of Nairobi, P. O. Box 29053-00625, Nairobi, Kenya

²Department of Plant Science and Crop Protection, University of Nairobi, Kenya.

³RUFORUM, Uganda.

⁴CIRAD, France.

⁵CTA, Netherlands.

⁶FARA

⁷Wagengen University, Netherlands.

Accepted 18 April, 2016

Abstract

Land degradation is a major problem in the semi-arid environments of Sub-Saharan Africa. Fighting land degradation is essential to ensure the sustainable and long -term productivity of the habited semi-arid lands. In Kenya, grass reseeding technology has been used to combat land degradation. However, despite the use of locally adapted perennial grass species namely Cenchrus ciliaris (African foxtail grass), Eragrostis superba (Maasai love grass) and Enteropogon macrostachyus (Bush rye) failure still abound. Therefore, more land is still being degraded. The aim of this study was to determine the main factors which contribute to failures in rehabilitating denuded patches in semi-arid lands of Kenya. A questionnaire was administered to capture farmer perceptions on failures on rangeland rehabilitation using grass reseeding technology. Rainfall data was collected during the study period. Moreover, rehabilitation trials using the three grasses were done under natural rainfall. Results from this study show that climatic factors mainly low amounts of rainfall to be the main contributor to rehabilitation failures. 92% of the respondents asserted that reseeding fails because of low rainfall amounts received in the area. The study area received a total of 324 mm of rainfall which was low compared to the average annual mean of 600mm. Reseeded trial plots also failed to establish due to the low amounts of rainfall received. This showed how low rainfall is unreliable for reseeding. Other factors namely destruction by the grazing animals, pests and rodents, flush floods, poor sowing time, poor seed quality, lack of enough seed and weeds also contribute to rehabilitation failures in semi-arid lands of Kenya.

Key words: Land degradation, grass reseeding, rehabilitation failures, low rainfall.

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (10), pp. 001-009, October, 2016. © International Scholars Journals

Full Length Research Paper

Agrobiodiversity endangered by sugarcane farming in Mumias and Nzoia Sugarbelts of Western Kenya

Godfrey Wafula Netondo¹*, Fuchaka Waswa², Lucy Maina², Tabitha Naisiko³, Nelly Masayi⁴ and Josephine K. Ngaira⁴

¹Department of Botany and Horticulture, Faculty of Science, Maseno University, P. O. Box 333- 40105, Maseno, Kenya.

²Kenyatta University, P. O. Box 43844-00100, Nairobi, Kenya.

³Uganda Martyrs University, P. O. Box 5498, Kampala, Uganda.

⁴School of Environment and Earth Sciences, Maseno University, P. O. Box 333 – 40105, Maseno, Kenya.

Accepted 28 April, 2016

Abstract

Commercial sugarcane farming has been practised in western Kenya for nearly forty years. This monocultural land use is associated with loss of natural vegetation and cropland, thus undermining food security status of a place. Further, sugarcane farming is a major contributor to loss of biodiversity in western Kenya. This study was therefore aimed at determining the long-term effects of sugarcane farming on indigenous food crops and vegetables in Mumias and Nzoia sugarbelts of western Kenya. Up to 188 respondents in three divisions of Mumias and 178 respondents of three divisions in Nzoia were purposively selected. These included small-scale and large-scale farmers. Data were collected using questionnaires, Participatory Rural Appraisal tool, interviews and field observations. Secondary data were obtained from documented materials. Land under indigenous food crops and vegetable has been declining since the introduction of sugarcane. Indigenous food crops and vegetable cultivation by farmers in the sugarbelts has been declining. Furthermore, some farmers have abandoned the growing of these crops altogether. Our results imply that sugarcane farming is a major contributor to agrobiodiversity erosion, but that there are also other important reasons such as change of consumer preference, land fragmentation, climate variability among others. In order to curb further loss of biodiversity, efforts should particularly focus on food crops and livelihood diversification and adoption of farming technologies such as agroforestry.

Key words: Biodiversity, farming, indigenous crops, monoculture, Western Kenya.

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (9), pp. 001-004, September, 2016. © International Scholars Journals 

Full Length Research Paper

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

K. Ofori-Frimpong*, A. A. Afrifa and S. Acquaye

Cocoa Research Institute of Ghana, P. O. Box 8, Tafo, Akim Ghana.

Accepted 10 April, 2016

Abstract

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.

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (9), pp. 001-006, September, 2016. © International Scholars Journals

Full Length Research Paper

Effects of temporal changes in climate variables on crop production in tropical sub-humid South-western Nigeria

Oluwasegun Olufemi Awotoye and Olaniran Jonathan Matthew*

Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife, Nigeria.

Accepted 05 April, 2016

Abstract

Climate variability and change have been implicated to have significant impacts on global and regional food production particularly the common stable food crops performance in tropical sub-humid climatic zone. However, the extent and nature of these impacts still remain uncertain. In this study, records of crop yields and some climatic variables for a period of 17 years (1990 - 2006) were used to carry out a comprehensive study of the impacts of climate variability on some common classes of food crops (tubers, grains, legumes and vegetables) in South -western Nigeria with a view to determining their responses to observed varying climatic conditions. Crops differed markedly in their responses to the climate variables. Mean temperature varied with the tuber crop production compared with other food crops. Production of other food crops (grains, legumes and vegetables) was largely dependent on the seasonal and inter-annual change in rainfall. However, combinations of a number of interacting factors with both climatic and non-climatic components were responsible for the relatively low coefficient of correlation (r 0.4) between rainfall amount and the crop yields. The climate projections for South-western Nigeria by 2020 would have direct and adverse impacts on food production, distribution, infrastructure and livelihood assets in Nigeria.

Key words: Climate variability, crop yield and production, regional climate projections, South-western Nigeria

African Journal of Tropical Agriculture ISSN 2375-091X Vol. 4 (8), pp. 001-008, August, 2016. © International Scholars Journals

Full Length Research Paper

Relationship between bacterial density and chemical composition of a tropical sewage oxidation pond

P. O. Olutiola¹*, K. O. Awojobi¹, O. Oyedeji¹, A. D. V. Ayansina² and O. O. Cole¹

¹Department of Microbiology, Obafemi Awolowo University, Ile-Ife, Nigeria.

²Department of Biological Sciences, Bowen University, Iwo, Osun State, Nigeria.

Accepted 19 April, 2016

Abstract

Studies were carried out to examine the performance of the sewage oxidation pond situated in and serving the community of the Obafemi Awolowo University, Ile- Ife, Nigeria. A survey of the coliform and total bacterial populations was carried out. The sewage was also examined for biochemical oxygen demand, dissolved oxygen content as well as for nitrate, phosphate, silica and chloride contents. The mean coliform bacteria counts decreased gradually from 69.1×10⁵ per 100 ml to about 10.1×10⁵ per 100 ml as the sewage moved through the oxidation pond into the receiving stream. A similar decrease in mean biochemical oxygen demand of the sewage from 397.8 Ib/acre/day to 64.2 Ib/acre/day was also observed. The concentrations of nitrate, phosphate and chloride decreased from the pond influent to the pond effluent. On the other hand, both the silica and dissolved oxygen content of the sewage gradually increased from 14.1 to 19.0 mg/l and 8.1 to 13.9 mg/l respectively, across the pond to the effluent. The coliform and total bacterial counts as well as the concentrations of most of the chemicals in the receiving stream increased after being joined by the sewage oxidation pond effluent. It is therefore concluded that the receiving stream was subject to both bacteriological and chemical pollution. Building of additional oxidation ponds or addition of a primary sewage treatment to the existing system is recommended for more efficient wastewater treatment.

Key words: Bacterial density, chemical composition, oxidation pond, sewage, tropics.