Effects of biochar on soil physico- chemical properties growth and yield of Brassica Napus

Author

LOURENE RUKONDO

Title

Effects of biochar on soil physico- chemical properties growth and yield of Brassica Napus

Abstract

The use of fragile marginal lands for crop production has led to the depletion of soil nutrients hence reduced agricultural productivity. Due to low productivity in the uplands, farmers have moved to cultivating fertile
wetlands, where they mostly grow market gardening crops, such as vegetables for sale to nearby cities. Unfortunately, productivity is also decreasing in the wetlands due to nutrient mining where inadequate amounts of inorganic and organic fertilisers are applied since they are expensive and most farmers cannot afford. Organic fertilisers are an option, but because farmers have few livestock, the manure is not enough. For those that can apply organic manures, the benefits are short lived due to rapid decomposition of the manure. Under these scenarios, the use of biochar as an organic amendment can be a sustainable option. Biochar, a carbonaceous material, can be used to improve soil fertility and crop productivity. This study assessed the effects of four types of biochar pyrolysed from four sources: maize (Zea mays) stover, pine sawdust, soya bean (Glycine max) stover and thatch grass (Hypharrenia filipendula) stover on soil physico-chemical properties and the growth performance of rape (Brassica napus). The biochar was incorporated into the soil just before planting in a randomised complete block design (RCBD) and replicated three times. The B. napus was grown during the wet season and dry season of 2015 at Glen Avilin farm in Shamva. Four weeks after transplanting, the B. napus was harvested weekly for six weeks and assessed for fresh yield, moisture content, leaf length and leaf area over a two month growth period. Soil samples were collected at 0-10 cm, 10-20 cm and 20-30 cm depths before biochar application; after the first crop and after the second crop and were analysed for water holding capacity, pH, soil carbon (C), mineral N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sodium (Na). At each sampling point and soil depth, an undisturbed soil core was collected for bulk density determination. Data were analysed using Genstat version 14. Results showed significantly higher (p<0.05) fresh weight yield, leaf length and leaf area in plots amended with biochar than the control in both wet and dry seasons. In both the wet and the dry season, biochar application rate of 20 t/ha had the highest yield, leaf length and leaf area of B. napus across all the biochar types. Nutrient content was significantly high (p<0.05) in the 0-10 cm depth in the wet and dry season. Soil sampling depth had a significant effect on bulk density and water holding capacity. It was concluded that biochar may be a better option for improving soil nutrition status and productivity of B. napus. However,

Date

2020

Publisher

BUSE

Keywords

Biochar

Brassica napus

Feedstocks

Supervisor

Mr J Gotosa