INFLUENCE OF DIFFERENT RATES OF FERTILIZER AND BIOCHAR AMENDMENTS ON SOIL, CARROT (Daucus carota) YIELD AND TUBER QUALITY IN RESPONSE TO CAPACITY NEEDS OF FARMERS IN THE TRANSITIONAL ZONE O

ABSTRACT 

Integrated Nutrient Management with biochar and inorganic fertilizer is critical to sustainable agriculture including the enhancement of production systems for climate change mitigation and adaptation. The objective of this research was to evaluate how soil management could be improved to respond to increasing environmental pressure on soil and crop in carrot production and to examine how anthropogenic changes in and management of soil affect crop growth, yield and nutritional quality. Mixed method approaches -sociological and field experimental research, were employed in the study. In the sociological study, action research was conducted to explore farmers’ perceptions, production constraints and production output to inform the choice of treatment for two field experimental studies conducted in 2016 and 2017 at the Multipurpose Crop Nursery of the College of Agriculture Education, University of Education, Winneba, Mampong Campus. The sociological study made use of cross-sectional, focus group discussion and stakeholder engagements. Respondents in the cross-sectional study were randomly sampled while those of focus group and stakeholder engagements were purposively sampled. The cross-sectional study engaged 25 carrot growers in Asante Mampong Municipality. The field experimental study was a 3 x 5 factorial arranged in Randomized Complete Block Design (RCBD) and replicated three times. Three levels of biochar at rates 0 ton/ha, 5 ton/ha and 10 ton/ha and 5 levels of inorganic fertilizer (NPK 15:15:15 at 200 kg/ha; P&K 50:50 at 50 kg/ha; P&K 50:100 at 50 kg/ha; D.I. Grow Liquid Fertilizer at 1L D.I. Grow: 200 L Water/ha; and No fertilizer) were used. The results showed that avocado biochar could be used to amend and improve soil density, porosity and moisture content and carbon stock to improve farmers’ capacity to adapt to environmental stresses and to mitigate climate change. Biochar integration with inorganic fertilizers also proved to significantly and variably affect soil physicochemical properties, crop growth, yield, yield components and nutritional quality.  In view of the varied market preferences of tuber quality, it is recommended for farmers to manage soils, crops and weather to specifically suite consumers and market preferences. It is recommended that farmers apply 10ton/ha biochar with P&K 50:50 at 50 kg/ha for improved water holding capacity, organic carbon composition and pH.  It is also strongly recommended that during the minor and major cropping season farmers respectively apply NPK 200kg/h + 5 ton/ha biochar and P&K 50:100 at 50 kg/ha without biochar for best marketable yield. In terms of root diameter, 5 ton/ha biochar without fertilizer is recommended for soils with average soil nutrients during the minor season. During the major season, it is recommended to apply P&K 50:100 at 50 kg/ha +10 ton/ha biochar for best root length. For best root diameter performance, it is recommended for farmers to apply P&K 50:50 at 50 kg/ha without biochar during the minor cropping season and P&K 50:50 at 50 kg/ha +10 ton/ha during the major season. For nutrition-informed carrot production NPK 200 kg/ha+10 ton/ha biochar is recommended for high protein carrot during the minor cropping season while major cropping season carrots should be produced with liquid fertilizer+10 ton/ha biochar. For high carotenoid carrots, it is recommended to apply liquid fertilizer+ 5 ton/ha biochar during the minor cropping season and NPK 200kg/ha +5 ton/ha biochar applied during the major season. Correlation between soil properties, carrot growth, yield and nutritional quality was also variable. There was significant effect of climate variability on carrot growth, yield, and nutritional parameters.