Date of Award
Doctor of Philosophy
Rice has displaced many traditional staples to become the second most important cereal after maize in Ghana. Domestic rice production has not kept pace with the increased demand, resulting in the importation of about 70% of rice consumed in Ghana, which costs about US$700 million annually. Rice demand is projected to grow at an annual growth rate of 11.8 percent. Despite the increased demand, average rice yield in Ghana is estimated to be 2.5 tonnes ha-1, while the attainable yield based on on-farm trials is 6–8 tonnes ha-1. Low inherent soil fertility, low rate of adoption of improved technologies, and policy distortions have been identified as the reasons for the low rice yield. The problem of low soil fertility is compounded by the inability of resource poor farmers to purchase finished fertilizer products for application and uniform fertilizer recommendations across agroecologies. The objectives of this study are to: (1) elucidate soil variability patterns of dominant lowland soils of the interior savanna of Ghana; (2) evaluate the effects of pyrolysis and calcination temperature on two locally available phosphorous (P) resources, (rice husk biochar (RHB) and Burkina phosphate rock (BPR) as a means of increasing P availability); (3) evaluate the two local P resources in a field trial to elucidate their effect on rice growth and yield and, (4) determine whether data captured using UAS technology can be correlated with key agronomic parameters in a lowland rice system. The results confirm the poor fertility status of these lowlands, in terms of very low levels of organic matter, ammonium, nitrate and phosphorous. At the Sampigbaa and Fuu sites, soil K, Ca, Mg, Na, clay and silt contents among other soil properties increased with increasing distance from the stream while P and sand showed a decreasing trend, probably reflecting deposition from overbank flooding. At the Doninga site, local relief, as captured by the digital terrain model (DTM) of the site, was more significant in explaining the pattern of variability, while the Tampola site showed variation characteristic of a toposequence or a catena. Pyrolysis of rice husk (RH) produces P-rich RHB and the formic acid (FA) extractable P content in the biochars increases with increasing pyrolysis temperatures. However, calcination of BPR decreased FA extractable P. The field trials showed that the same yield enhancing effect can be obtained when BPR is directly applied to the soil without calcination, and the best grain yields are attained when inorganic P is combined with RH or RHB. Finally, remote sensing using UAS, can be used to cheaply acquire high resolution spectral indices that correlate many agronomic parameters of rice crop. Overall, the study showed that variability of seemingly homogenous lowlands of the interior savanna of Ghana can be mapped for management, while local P resources could be exploited for increased productivity of rice.
Avornyo, Vincent Kodjo, "Increasing rice productivity in the lowland soils of the interior savanna of Ghana: The role of rice husk biochar and phosphate rock" (2019). Graduate Theses and Dissertations. 16967.