Fertilizer recommendations for maize and rice based on participatory Nutrient Omission Trials

Abstract

The main constraint of agriculture in Togo is soils' low content in nutrient and organic matter. Inappropriate land use, poor management and limited use of mineral fertilizers have led to the degradation of agricultural lands. Consequently, crops yields are significantly and continuously declining. For crops such as maize and rice, yields are lower than 1.5 t/ha. Even fertilizers applications on these crops are inefficient because fertilizer recommendations dating back to over 40 years are obsolete and inappropriate. Existing fertilizer types and recommended rates have become inappropriate due to continuous nutrient exports by crops without their return to the soils. Moreover most of these recommendations have been developed without taking into account the specificities of the various agro ecosystems, to be applied uniformly throughout the whole country. Given this situation, many research works were carried out on maize and rice fertilization. Interesting results were achieved but not disseminated due to low level of collaboration between research, extension, farmers and decision makers. To address this issue, from 2011, Participatory Nutrients Omission Trials (PNOT) were conducted in the five regions of Togo by IFDC and partners, then from 2012 to 2014 in the framework of the Project to Support Agricultural Development in Togo (PADAT) involving 16,000 farmers and 111 technicians and specialists trained on Integrated Soil Fertility Management (ISFM). It was concluded that about 89% of soils are low in nitrogen identified as the major limiting nutrient to crop yields in PADAT areas. The main fertilizers available in the country are NPK (N -15%, P2O5- 15%, K2O -15%) and Urea (46% of N). The conclusion was that, in the short term, farmers should be advised to use 150 kg of NPK + 150 kg of Urea per hectare on maize and rainfed rice. However, it is necessary that single fertilizers such as Urea, TSP, and K2SO4 be available for participatory soil fertility diagnosis (PSFD) to facilitate sound decision making. In view of the outcomes, the diammonium phosphate (DAP) could be recommended to maize and rice producers, as most soils have sufficient levels of potassium. The PSFD should be a continuous process and results widely disseminated to help farmers correct soil nutrient deficiencies as soon as they appear in time and place.