The benefits of biochar on soil nutrient retention and maize productivity

Abstract

Poor soil fertility is one of the major factors contributing to low production and productivity among smallholder farmers mainly due to soil acidity, low nutrient reserves, low nutrient retention and low soil organic matter. The use of biochar technology in crop production has the potential to alleviate these problems. The study aimed at determining the benefits of biochar on soil nutrient retention and maize productivity. The biochar was produce from maize combs by Pyrolysis using the Top Lit updraft kiln. For the effects of biochar on nutrient retention in the soil profile, 50cm length, 8.3cm diameter soil columns, were used to collect soils from Kabwe, Mufulira, Choma and Mungu research stations. The treatments comprised: biochar+fertilizer, fertilizer alone, and control. Biochar and fertilizer application rates were: 2% wt/wt biochar/soil (@40 t/ha) to the top 10cm and 9g (200kg/ha) “D” compound to the top 5 cm, replicated four times. Rainwater was used to leach the soil. The EC and the pH of the leachate was measured for 12 weeks. Biochar effect on maize grain yield, was conducted at the above sites with similar treatment as above. The soil profile samples were also collected at 0-15cm, 15-30cm and 30-50cm depths from control, fertilizer alone and biochar+fertilizer treatments. The results show that biochar effect on nutrient leaching was varied depending on the soil types. Biochar addition restricted the leaching of D compound nutrients but enhanced the leaching of Urea in Kabwe and Choma soils. The field profile samples revealed that biochar reduced leaching of nutrients. Furthermore, biochar amendment increases the CEC and soil pH thereby ameliorating soil acidity and improving the soil chemical characteristics. The retention of these nutrients ensures an efficient use of applied synthetic fertilizers by the plants thereby increased maize yields by 88% compared to fertilizer alone treatment in Choma, 28% in Kabwe, and 22% in Mufulira soils.  The study showed that biochar applied to the soil significantly reduced the leaching of plant nutrients, increased soil pH, CEC, available phosphorus, mineral nitrogen, therefore offers great potential to enhance soil quality and improve crop yield.