Development of nutrient management strategies along a continuum of dairy production intensification in Uganda
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Soil fertility decline is a leading form of land productivity degradation in Sub-Saharan Africa. Colossal quantities of nutrients are removed annually from soils, especially through crop harvests, unreciprocated by nutrient inputs. This is true for both crop and livestock centred production systems in the region. Moreover, with prudent management, the integrated crop-livestock system offers better opportunities for nutrient management particularly within the low resource endowed small scale farmer production framework. Livestock plays a critical role in the socio-economic setting of the region. In Uganda, livestock contributes 20% of Agricultural Gross Domestic Product (AGDP), and is a principal sector income generation and food security for the population. Of the livestock sector contribution to economy, the dairy sub-sector accounts for 40-50%. Within the sub-sector exists a spectrum of the production practices along with a diversity of levels of production. Furthermore, the gap between production and the demand for dairy products is spiraling, owing to the increasingly low levels of system productivity. Among the major causes is soil fertility decline, likely due to negative nutrient balance sheets. As such, efforts to develop appropriate interventions ought to hold this as the critical entry-point. In this case, the starting point is the need for a clear understanding of the dairy systems across the country, particularly in terms of management and levels of intensification. On the basis of such efforts, a systematic layout of the dairy systems structure will be achievable within which a critical trail for nutrient flow can be traced, mapped and realistic interventions mounted. It was within this h e w o r k that this research was conducted. The objectives of the study were to: (i) Establish farm categories on the basis of dairy intensification in Uganda for targeting nutrient management interventions; (ii) Evaluate the effect of dairy intensification on major plant nutrient balances as a mechanism for identifying entry-points for intervention and subsequent contribution to sustainable productivity of dairy systems; (iii) Identify indicators of nutrient status for assessment of dairy production systems; and (iv) Identify options for improving nutrient balances at various levels of intensification of dairy production in Uganda. Studies were conducted in the districts of Jinja, Masaka and Mbarara in Uganda in two parts, namely (i) a cross-sectional characterisation of dairy systems; and (ii) a longitudinal study of nutrient flows and their management. The characterisation study, which lasted three months, involved three sub-counties per district and these were selected based on agro-ecology, b a n population and intensity of transport network. Within each sub-county, 37 households were selected from two villages. A semi-structured questionnaire was then administered to one adult per household. Key elements of the questionnaire were household structure, land size, crops and their yields, livestock types, numbers and productivity-, livestock management systems and household incomes. From this study, 4 major dairy categories were identified, namely, Herding (HD), Tethering (TE), Fenced (FE) and Zero grazing (ZG), in order of increasing intensification of production. The HD category was characterised by (i) low herd content of improved cattle breeds (21%), (ii) low expenditure on veterinary services (Ushs 71,368 year-'), (iii) moderate use of long term hired labour (1.1 persons farm-'), and (N) very low off-farm income (Ushs 5,846 The TE category was similar to the HD in improved cattle breed content but was moderate in expenditure on veterinary services and long term labour. Off-farm income which was very high (Ushs 65,111 month-') was the exception in this category. On the other hand, the FE category was outstanding in long term labour use (1.6 persons farm-') and off-farm income (Ushs 200,667 month-'). Contrastingly, ZG was exceptionally high in improved breeds and expenditure on veterinary services, but very low (0.5 persons farm-') long term labour use. From the characterisation study part, 19 farms were drawn and used in the longitudinal study. Farm selection ensured representation of the four categories described above. However, out of the ZG category, a new category named Semi-Intensive (SI) was created to cater for the unique features that were evident in the interphase between ZG and FE. Overall, each category was represented by at least three farmers as replicates. Each Farm was examined in terms of arable land (hereafter referred to as Land) and the livestock component with focus on dairy production. The Land was considered to have a variety of Patches. A Patch in this context is a subdivision within arable land (Land) representing a different crop or crop mixture grown thereon. The f m selected varied in total land area, ranging from 0.4 to 28 ha, with 1 to 30 heads of cattle. The study was ran for three cropping seasons during 2003-2004. The main study parameters included herd dynamics, milk yields, livestock feeds, land allocation to crops, fodder and pasture, crop harvests, soil fertility management practices and generally all farm imports and exports. From this study, the largest nutrient influxes into the Farms were those into the ZG category and least into FE, with differences between the two amounting to 35,200 and 320-folds for N, P and K, respectively. Off-farm feeds were responsible for the large nutrient influxes into the farms and in the case of N, biological N fixation (BNF) made a substantial contribution. Nutrient inflows to the f m through direct applications from off-farm were negligible in all categories. The major channel for N, P and K outflows from the Farms was through crop harvests, with the largest values in the ZG category, and lowest in HD. The outflows Â£corn the ZG category amounted to 10, 11 and 5-folds those in the HD category for N, P and K, respectively. From the Land standpoint, the highest N influx was in the TE category, and was 7-folds that in the HD category, which was the lowest. The greatest contributor to N inflows to the Land was BNF. Phosphorus and K entries into the Land were again highest in TE, but lowest in the SI category. The P inflow value for TE was 20-folds that for the SI category, but 19-folds in the case of K. Oufflow values for Land N, P and K were highest in ZG category with a range of 7 - 13-folds those in the HD category which had the lowest values. Farm N, P and K inflow to outflow ratios were greater than unity, with the exception of those in the FE category, and for K in HD, which had less than unity values. The highest Farm N inflow to outflow ratio (3.2) was in the TE category, yet for P it was in ZG (4.2). In contrast, the highest K Farm inflow to outflow ratio (5.2) was in the SI category. Land inflow to outflow ratios were all <I, with highest ratios in N (0.7) and P (0.5) occurring in TE, while the FE category had the highest Land K inflow to outflow ratio of 0.2. Differences between values of Farm N, P and K balances and their Land counterparts were persistently highest in ZG and lowest in HD and FE. Dairy intensification, to an extent, had a positive effect on Farm N, P and K balances, while the contrary was true for Land balances. With respect to Farm nutrient balance sheets, ZG category had the largest positive N, P and K values. On the other hand, FE presented the poorest scenario, with all consistently negative net balances. At arable land (Land) level, TE category presented the highest positive N balance (1.1 kg ha-' season-'), while HD had the highest but negative P and K balances (-0.6 and -4.1, respectively). At Land level, on basis of crop patterns, Fodder crops presented the lowest and negative N, P and K net balances, and these were -54.7, -8.6 and -85.9 kg hS1season-', respectively. Contrastingly, the Beans-Maize crop pattern had the highest positive N balance (8.7 kg ha-' season"), while Banana-Beans had the highest P balance (1.5). The highest K balance (-2.6) was in the Pasture crop pattern. Factors related to land size, crop patterns, harvests, grazing and inputs to the land were identified as major indicators for N, P and K balances. Among these indicators, manure use was identified as the major option for improving nutrient management. Quantities of manure required to offset N imbalances on the Land were established using the indicators identified and Patch balances. The largest quantities of manure required for offsetting land N imbalances were among the more intensive farm categories with the highest value (1665 kg (DM) ha-' season-') in the ZG category and least in the less intensive categories with the lowest value (298 kg (DM) f ha-' season-') in the HD category. Manure available on farms in FE and TE was adequate to offset N imbalances on the Land; however, additional external nutrient inputs would have to be obtained in the HD (367 kg (DM) of manure), SI (410 kg (DM) of manure) and ZG (17 410 kg (DM of manure) categories. Biological N fixation (BNF), with the ability to raise N balances, was also identified as a viable option for improving nutrient management. Basing on yield response functions developed from regression models, manure application of 500 kg (DM) ha" season-' to the Land, could predictably increase yields of banana by 13%, amounting to Ushs 331,850; and elephant grass by 48% also amounting to Ushs 717,210, Ceteris Paribas. In a nutshell, this study has demonstrated that: (a) dairy systems productivity improvement is better tackled on basis of dairy intensification categories; (b) the most intensified systems attract more nutrient inflow but this is not translated into proportionate inflow of nutrients into the arable land (Land), which is a situation that signals inefficient management of nutrients within the Farm. Among the bottlenecks to nutrient transfer into the Land was the non-utilisation of cattle manure as a fertility input for crop and fodder production; (c) biological N fixation contributes a significant in-situ N input though the level of contribution is far less than the external feed inflow in the more intensive categories (ZG and SI). Therefore, focal attention on enhancement of BNF, particularly for the small scale farmers, offers a window of opportunity for elevating productivity of the crop dairy system; (d) key factors that influence nutrient management provide inference on nutrient balances and are relevant for development of options for nutrient balance improvement; and (e) improved utilisation of manure could potentially improve crop and fodder yields.