Suitability Assessment of Arable land use for Greengram Production at Makerere University Agricultural Research Institute
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Arable land suitability assessment was conducted at Makerere Agricultural Research Institute, Kabanyolo (MUARIK) to assess the potential and actual suitability of fallow, grass and cultivated land use for green gram production. The methodology used for evaluation of land suitability was based on FAO (1976), which consists of matching land characteristics against crop requirements and assigning a suitability rate for each land characteristic. The field was divided and arranged in a completely randomized block design with soil samples from different arable land uses on lower and upper slopes as blocks and a total of 30 soil samples was collected, 10 from each of the fallow, grass and cultivated land uses and on upper and lower slopes. Soil physical and chemical properties, including texture, pH, exchangeable bases (K, Na and Ca), total nitrogen, available P and Soil organic carbon were determined. Results show that the texture of the soils was sandy. The soils were acidic with pH of 5.22 (fallow land), 5.15 (grassland) and 4.94 (cultivated land). All the three forms of land uses were deficient in most of the minerals, including P (2.59-4.05 ppm), K (0.079-0.140 cmol(+)/kg), Na (0.048-0.056 cmol(+)/kg) and Ca (0.034-0.107 cmol(+)/kg). Soil organic carbon (1.68-2.30%), organic matter (2.89-3.97%) and total nitrogen (0.15-1.21%) were all in the critical range for green gram production. On comparison with standard requirements for green gram production, fallow land soils had moderate potential suitability (S2) and marginal (S3) actual suitability for green gram production due to deficiency of important essential primary plant nutrients, especially K and P. Grassland had moderate potential suitability, though compared to fallow land, it had lower magnitude for potential suitability for green gram production. The limitations of grassland for moderate actual suitability were lack of essential primary plant nutrients (P and K and exchangeable bases), which makes the land marginally suitable green gram production. Cultivated land was marginally suitable for green gram production in terms of both actual and potential suitability (S3). The pH of the soil was not suitable for green gram growth and together with very low bases, it puts more constraints on green gram production. For improved growth and yield of green gram on all the three land uses, appropriate lime, organic amendments, inorganic fertilizers (P and K fertilizers), together with appropriate soil management practices, are required.