CLIMATE-SMART AGRICULTURE: INCREASING CROP YIELDS ONFARM THROUGH USE OF SUNNHEMP (Crotalaria juncea L.) PHASE 2. RESIDUAL EFFECTS OF SUNNHEMP ON SUCCEEDING MAIZE CROP

Abstract

Agriculture in Swaziland, like elsewhere in the region, faces a number of challenges like stagnant agricultural yields, land degradation and poor access to farm inputs. Climate-smart agriculture is an approach to developing the technical, policy and investment conditions to achieve sustainable agricultural development for food security under climate change. A field experiment was established in the 2015/2016 cropping and was continued in the 2016/2017 cropping season. The main objective of the study was to increase crop production on-farm by using green manure crops instead of commercial fertilisers, whose manufacturing process contribute to climate change and climate variability, through the emission of greenhouse gases. The treatments in the 2016/2017 season were; (1) Maize monocrop; no fertiliser. (2) Sunnhemp monocrop at 80 kg/ha. (3) Maize monocrop with fertiliser; applied 300 kg/ha of 2-3-2 (22) and 200 kg/ha of LAN (4) Maize and sunnhemp intercropped, no fertiliser to maize, sunnhemp seed rate is 40 kg/ha; both crops allowed to mature and crop residue are returned to the soil after harvest (5) Maize and sunnhemp intercropped, no fertiliser to maize, sunnhemp seed rate is 60 kg/ha; both crops allowed to mature and crop residue are returned to the soil after harvest. The results show that sunnhemp in monoculture was significantly (P < 0.05) higher in dry mass with 4391 kg/ha at 10 weeks after planting while sunnhemp intercropped with maize was lowest with 2764 kg/ha. The results also show that sunnhemp yield was not significantly different among the different treatments. Maize grown in monoculture with the application of synthetic fertilisers yielded significantly (P < 0.05) higher with 3800 kg/ha. Maize grown in monoculture without fertiliser followed with 3367 kg/ha while maize intercropped with 40 kg/ha of sunnhemp was lowest with 1067 kg/ha. The land equivalent ratio in this experiment was positive at 1.58. It is concluded that the residual effects of a previous sunnhemp crop did not contribute significantly to maize performance in the current season. It is recommended that the experiment be continued on a long term basis as benefits of green manures need progressive cropping seasons.