The aim of this study was to evaluate the soil fertility status of selected coffee growing districts of Northern Tanzania and recommend immediate and long term soil management intervention strategies. The study was conducted in Hai and Lushoto Districts, between May and September, 2011. A total of 116 soil augerings and 10 soil profiles were described, and soil samples analyzed for the key fertility parameters. These were evaluated qualitatively by assigning scores against the requirements of Arabica coffee, and quantitatively by calculating the total soil-available nitrogen, phosphorus and potassium. Spatial assessment of the total soil-available nutrients was done using ArcView GIS 3.2 and ArcGIS 9.3. Soil fertility was found to be considerably low in the study areas, much lower in Lushoto than in Hai. Limitations common to both districts are low P and micronutrients, while the additional ones specific for Lushoto are low cation exchange capacity and exchangeable K. Spatial interpretation revealed interesting trends, which could be explained from the topography of the area and/or the farming practices common in the area. The results are discussed in this paper, and recommendations on appropriate integrated soil fertility management strategies are put forward.

This work was carried out in collaboration between all authors. Author GPM designed this study, managed the analysis of the study, wrote the protocol and wrote the first draft of the manuscript. Authors JPM, BMM and JMT managed the literature searches. Author BHJ provided all the ideas of his model QUEFTS, on which this work was based and also contributed in literature searches. All authors read and approved the final manuscript.

The aim of this work, as an extension to SAFERNAC model, was to establish economically optimum combinations of N, P and K application to Arabica coffee in the Northern coffee zone of Tanzania. The study was conducted in Hai and Lushoto districts between 2010 and 2012. Prices of nutrient inputs and those of parchment coffee were introduced into the original SAFERNAC model, which was used to obtain yields from a soil of known properties receiving different levels of input N, P and K from both organic and inorganic sources (ISFM). The costs of these were derived from experience in Northern Tanzania, while coffee prices were estimated to range between 1250 and 2500 TZS kg-1. The result was economically optimum N:P:K ratios that give highest net returns and value : cost ratios in situations of low, medium and high soil fertility. It was also shown that farmers' decision to deviate from the optimum and the allowable level of such deviation, depend much upon the prices of nutrient inputs in equivalent terms. In the medium-fertility situation (which applies in the study districts), the highest yield increment was noted with the maximum amount of N and P. The optimum application rate was 310

The aim of this study was to establish the nutrient release potential of different organic materials and assess their role in integrated soil fertility management for coffee using the new coffee yield model SAFERNAC. It involved an incubation experiment conducted at TaCRI Lyamungu Screenhouse for 180 days between April and September 2011. Cattle manure, coffee leaves, pulp and husks, Albizzia leaves and four green manure plants -Mucuna pruriens, Lupinus albus, Canavalia ensiformis and Crotalaria ochroleuca were mixed with two soil types -Eutric Nitisols from Lyamungu, Hai district and Humi-Umbric Acrisols from Yoghoi, Lushoto district. The mixing ratio was 5% organic to soil, the mixture was moistened to FC and incubated in 10 litre plastic containers arranged in RCBD (10 treatments and 3 replications) at room temperature. Duplicate soil samples were taken at day 0, 3, 8, 15, 26, 45, 74, 112 and 180 and analyzed for NH 4 + -N, NO 3 -N, available P and exchangeable K. The cumulative N min , P and K values resulting from the treatments were used to estimate their relative contribution to the soil nutrient pool and

The aim of this work was to explore the behavior and usability of the new model SAFERNAC over coffee growing areas throughout Tanzania. Soil fertility data from 1,131 georeferenced points in three zones were fed into the model under four distinct approaches – baseline (no input), organic (manure), inorganic (NPK) and combination of manure and mineral fertilizer. The simulated yields were descriptively compared per zone. They were loaded into QGIS 3.2, interpolated using the Inverse Distance Weighting (IDW) algorithm and the resultant raster maps clipped on basis of digitized boundary shapefiles. Baseline yields were effectively computed from 99.2% of the surveyed sites. The model showed high sensitivity to pH, which has a greater influence on P than N or K. Calculated yields decreased in the order Zone 2 > Zone 1 > Zone 3. The difference in yield between NPK 160:80:80 alone and a combination of NPK 80:40:40 (half dose) plus 5 tons manure was neither quantitatively nor spatially significant. SAFERNAC has proved its usability across the Tanzanian coffee soils, in simulating yield of parchment coffee. The combination approach (organic materials and mineral fertilizers) is most appropriate, as it can reduce the fertilizer cost by about 50% without seriously compromising the expected yields.