Soil fertility status of abandoned fields in smallholder agriculture in South Central Zimbabwe

Abstract

In Zimbabwe, because of shortages of land, there is need to establish whether soil fertility improves over time in abandoned fields. A study was undertaken in 2015 to characterize fertility status of abandoned fields in smallholder farming areas located in Buhera and Hwedza districts in Zimbabwe. Abandoned fields were divided into four categories based on years of being abandoned (0–5, 6–10, 11–20 and ≥ 20 years) across two soil types and agroecological gradient made up of four regions (AER II to V) where annual rainfall decreases from AER II to V. Soil samples were analysed for pH, N, P and K using standard laboratory methods. A survey was conducted to determine adequacy of nutrient resources used. Soil nutrients did not significantly vary (p > 0.05) with period of abandonment but varied with soil type and agroecological regions. Clay soils and soils from AER V had significantly high N, P and K content. In terms of adequacy of nutrients across all the three factors, N and P content were below required recommendations for crop production whilst K was adequate and soil pH was too acidic. With regards to fertilizer use, majority of the farmers failed to purchase mineral fertilizers because their annual cash earnings were far below money required. As a result 91% of the farmers were failing to apply recommended fertilizers for sustainable yields. In conclusion, abandoned fields in Zimbabwe's communal areas do not restore soil fertility regardless of period to which a field has been abandoned, soil texture or agroecological region. The fertility of these abandoned soils remains poor and too low for crop growth. Farmers are financially unable to meet soil nutrient requirements to improve fertility of their abandoned soils. These findings are important in determining appropriate measures to restore soil fertility and in determining efficient land use policing and planning measures.