Soil fertility analysis associated to land use in Eastern Uganda. B1

Gachimbi Louis N., Maitima Joseph. 2004. Soil fertility analysis associated to land use in Eastern Uganda. B1. Bruxelles : European Union, 36 p. Autre type de numéro : PROJECT N°7.ACP.RP.R.578, N° de rapport : FITCA EMMC N°B1

Résumé : A total of 191 soil samples were collected from different land uses in the four sites (Tororo, Iganga, Kamuli and Soroti Districts) in Uganda for soil fertility and texture analysis. Soil fertility in respect to organic carbon (organic matter), total nitrogen, available phosphorus, exchangeable potassium, and trace elements were variable but generally ranged from adequate to deficient with a lot of variations across sites and within sites. Mean organic carbon varied from very low (1.41% organic C) in Tororo to adequate (2.27% Organic C) in Iganga. The same trend was observed for total nitrogen, which also varied from very low (0.14% N) in Tororo to adequate (0.26% N) in Iganga. Only one site had adequate carbon levels with the rest (Tororo, Kamuli and Soroti) having low organic carbon levels. This was due to nitrogen fixing crops grown in Iganga (e.g. groundnut), level of inorganic fertilizers applied in coffee or maize farms and substantial bush/fallow fields (47%) in this site unlike in the other sites where no nutrients are added. Available phosphorus ranged from very low (4ppm) to luxury amounts (91 ppm) but the mean available P was low throughout the four sites (4-15ppm). Out of the four sites, 31% and 20% of sites in Tororo and Iganga respectively had potassium deficiency 15% of the farms in the other sites had deficiency problems. Trace elements ranged from very low to luxury amounts or consumption in some sites. In Soroti and Tororo, 100% and 96% land uses respectively had deficiency in zinc levels while 42% and 40% of the points in Kamuli and Soroti respectively were deficient in iron. However, the level of copper in all the sites was almost adequate (82%) in most of the land uses except in few places. Mean soil PH in the four sites indicated that the soil reaction was ranging from strongly acidic (PH <4.5) to medium acidity (PH <6.0). The range in soil PH was from PH 3.61 to PH 7.19. Both non-acidifying and acidifying fertilizers need to be selectively used depending on the soil PH at respective sites. The soil texture analysis showed that soils sampled from the four sites had a mean textural class of sandy clay loam (SCL). At the extreme range e.g. Tororo the soils are of clay nature usually dark/black clacking clays. This implies that the soil have been slightly eroded leading to poor soil fertility problems. FYM or compost must be added to modify the soil texture and improve its water holding characteristics. At Kamuli, Soroti, Iganga and Tororo sites, apply farmyard manure (FYM) or compost at 5t/ha to raise soil organic matter, PH and supply sufficient nitrogen to most of the crops. Apply 2t/ha of lime on maize/millet, maize and coffee at Soroti and Kamuli sites to raise the soil PH to between 5.5 and 6.5 required by most crops for optimal crop growth. It is recommended that compound fertilizer containing N: P: K 17:17:17 at 300kg/ha per year be used at planting time to correct nitrogen, phosphorous and potassium (NPK) deficiencies in the soil for common crops. For coffee, apply one debe or 1 Okg/tree of FYM or compost around the tree base; apply further 50g of TSP by broadcasting around the tree/year and top dress with 25kg/10tonnes CAN or ASN per year in alternate years. Apply 25kg of ASN to coffee at nursery. For maize in all sites top dress with 250kg/ha sulphate of ammonia in two portions at knee high and at flowering stage. Crop diversification noticed in most sites is recommended to utilize available nutrients and for crops to complement each other e.g. maize/groundnuts in terms of nutrients. Foliar feed containing zinc and iron is recommended for application on tree crops like coffee and bananas due to its scarcity in most sites.

Classification Agris : P35 - Fertilité du sol
P33 - Chimie et physique du sol
F01 - Culture des plantes

Auteurs et affiliations

• Gachimbi Louis N.
• Maitima Joseph, ILRI (KEN)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/576797/)

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