Medium-term Impact of Conservation Agriculture on Soil fertility in Dryland Millet fields in Northeast Namibia
No Thumbnail Available
Date
2023-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Namibia University of Science and Technology
Abstract
Smallholder farmers in Northern Namibia have been experiencing poor crop production in recent years, making it difficult to meet household consumption demand. The poor crop output is attributed to poor soil fertility, sporadic rainfall, and high temperature. To address this issue, MAWF and GIZ collaborated to train small-scale farmers on Conservation Agriculture (CA) practices in the northern regions of Namibia. CA is being considered as a farming system having the potential to improve soil fertility and providing stable yields. However, there are concerns raised about the shortage of evidence of the advantages of CA for small-scale farmers in Southern Africa, specifically on soil fertility. A study was therefore conducted in KE and KW to evaluate the medium term (6 years) impact of CA on soil fertility from 2016/2017 to 2021/2022 seasons. Prior to CA implementation soil samples were collected in designated CA fields at a depth of 5-30cm and soil samples were continuously collected at least after every season. Soil samples were taken to the soil laboratory for analysis of physicochemical properties such as pH, OC, N, K, P, Ca, Mg, Zn, Fe, CEC, Al, Si and soil texture, using the Bruker Alpha I spectrometer. The study analysed data for 17 farms from 2016 to 2022. The study findings indicated that there was no significant impact of CA on soil fertility in a period of 6 years. It was observed that, soil elements remained relatively low while the potential toxic elements remain relatively higher over the years. There was statistically significant difference (p < .002) in soil pH under CA. However, the average pH in the 6th year, (5.76±1.00) was lower than the threshold and that of the first year (6.55±0.70). CA did not have any significant improvement on SOC/SOM (p > 0.05) K (p > 0.05), P (p > 0.05), Ca (p > 0.05), and Fe (p > 0.05). There was a significant decrease in N (p <.001) from a mean value of 0.40±0.22 g Kg-1 in 2016 to 0.27±0.18 g Kg-1 in 2022. Zn was also significantly decreasing (p<.001) over the years. Si remained relatively high while Al levels remained consistently low. CEC was low and decreased significantly (p<.001). Mg was high in first years, but it reduced significantly (p<.001) to the required range. The correlation analysis revealed positive relationship between pH and various nutrients, including N, K, Ca, Mg, CEC, Zn, Fe, and Al. OC showed a positive correlation with N and CEC, and there was a weak positive correlation between OC, Ca and Mg. CEC exhibited a positive and significant relationship with OC, N, K, Ca, and Mg. In conclusion, the research findings indicated that there was no significant improvement in soil fertility under CA over a period of six years in Northeast Namibia.
Description
Thesis submitted in partial fulfilment of the requirements for the degree of Master of Natural Resource Management at the Namibia University of Science and Technology
Keywords
Smallholder farmers, conservation agriculture, crop rotation, permanent soil cover, minimum tillage, soil fertility
Citation
Sikoka, T. H. (2023). Medium-term Impact of Conservation Agriculture on Soil fertility in Dryland Millet fields in Northeast Namibia [unpublished masters thesis]. Namibia University of Science and Technology.