Climate, trees and agricultural practices: Implications for food security in the semi-arid zone of Sudan

Livelihoods are precarious in arid and semi-arid regions, such as Sudan, as the main food crops are often grown in production systems that heavily depend on climatic conditions and appear to be threatened by several factors. Over 70% of Sudanese are farmers who rely mainly on rain-fed agriculture to secure their livelihoods. Their crop cultivation is constrained by such factors as climate change and variability, as well as low soil fertility, which is aggravated by limited agricultural inputs. Indigenous legume trees, such as acacias, can potentially alleviate the vulnerability of these systems. In practice this is possible by integrating trees with agricultural crops on the same piece of land, thus forming an agroforestry system. Nevertheless, the adoption of agroforestry also remains constrained by several factors, including unclear tree tenure and small farm size. The main objectives of this research were: (I) To classify and compare various land-use systems so as to facilitate an analysis of the socio-economic impacts of farming practices in the semi-arid zone of Sudan; (II) To define the determinants and constraints for agroforestry based on the integration of natural acacia trees with agricultural crops, thus forming the agroforestry parkland system in Sudan; (III) To identify and analyse the main factors underlying the variability of crop yields during the period 2001–2010; and (IV) To characterize the impact of land-use changes between 1972 and 2010 on natural forests and land productivity. The research was conducted at two distinct sites, El Dali and El Mazmum in Sennar state, Sudan (latitudes 12° 5ʹ and 14° 7ʹ N and longitudes 32° 58ʹ and 34° 42ʹ E, respectively). Principal data on households and crop yields were collected from 281 randomly selected households in face-to-face interviews using a pre-structured questionnaire. Soil and rainfall data along with satellite images were obtained from associated institutions in Sudan. Qualitative and quantitative methods were used to analyse crop and household data, and the Excel template MAKESENS was used to study the rainfall data. GIS software applications and economic analysis were used in clarifying land-use changes and crop profitability with various land-use systems, respectively. Agroforestry parklands that consist of the integration of acacia trees with agricultural crops were found to financially be the most profitable system, offering higher crop yields than monoculture systems. The number of people in a household, agro-ecological location, incentives from agricultural associations, and land holding size were the main drivers for farmers to combine acacia trees with agricultural crops, forming an agroforestry parkland system. Constraints for practicing agroforestry included insecurity of tree ownership, poor interaction between farmers and extension agents, lack of tree planting materials (in cases where a farmer would have adopted tree planting as a method to increase the tree cover), uncontrollable livestock movements on farms, and land owners’ preference to rent their entire holding to landless farmers. The yields of most of the studied crops (sorghum, pearl millet and sesame) were affected by interannual variability in rainfall rather than agricultural practices. Land use and land cover have remarkably changed over time, resulting in a negative impact on soil properties and crop performance. This research concludes for the region now studied in Sudan that climatic variability, low soil fertility and inadequate agricultural inputs contribute to a decline in crop yields. The lack of an appropriate tree tenure regime constitutes the strongest disincentive factor inhibiting farmers from practicing agroforestry, obviously the best available land-use option for sustainable crop cultivation and securing rural livelihoods.