RESIDUAL EFFECTS OF SUNNHEMP (CROTALARIA JUNCEA L.) AS A GREEN MANURE CROP ON A SUCCEEDING MAIZE (ZEA MAYS L.) CROP ABSTRACT C. M. Mthethwa, O T Edje and. G. N. Shongwe Introduction and Problem Statement. Maize is the staple crop in Swaziland but there have been shortfalls in production due to high cost of commercial fertilisers among other factors. One possible means of addressing the problem is the use of sunnhemp (Crotalaria juncea. L), a green manure crop. Objective. The objective of the experiment was to determine whether the use of sunnhemp, as a green-manure crop can be a substitute to commercial fertilisers. Materials and Methods. A field experiment was conducted at the Crop Production Farm of the University of Swaziland, during the 2008/2009 cropping season. The design of the experiment was split-plot. The main plots, which were planted to sunnhemp in 2007/2008 crop season consisted of: (1) fallow land (2) sunnhemp mowed at full flowering and not incorporated into the soil (3) sunnhemp incorporated into the soil at full flowering , and (4) sunnhemp allowed to mature. In the 2008/2009 crop season, three fertiliser treatments, the sub-plots, were superimposed on the preceding sunnhemp crop. These treatments were: (1) control, (2) 200 kg/ha 2:3:2 (22) fertiliser + 200 kg LAN and (3) 400 kg/ha 2:3:2 (22) + 400 kg LAN. Each sub-plot treatment was replicated four times. Maize variety, SC403, was the test crop. Data on morphological, physiological, and yield were collected. Results. The result of the nitrogen content analysis showed that in the fallow plots, only 14.4% N was added into the soil while 21.4% was added where the sunnhemp was not incorporated. There was 81.5% N added into the soil where the sunnhemp was incorporated while 47.7% N was added where the sunnhemp was allowed to mature. There was a significant (P < 0.01) difference for most of the data collected. The seed yield where the sunnhemp was allowed to mature was the highest (7873 kg/ha). The fallow main plots had the lowest seed yield (6546 kg/ha). The mean yields of commercial fertiliser levels, averaged over sunnhemp treatments, for 0, 200, and 400 kg/ha were 6729 kg/ha, 7970 kg/ha, and 7145 kg/ha, respectively. Conclusion. It can be concluded that the maize crop benefited from the residual effect of sunnhemp as treatments where there was sunnhemp performed better than those where there was no sunnhemp. Recommendation. It is recommended that farmers who can afford planting sunnhemp on fallow land as a means of building up soil fertility for sustainable crop production plant sunnhemp to be followed by maize in a sunnhemp/maize rotation complex. Index words: Green manure crops, biofertiliser, sunnhemp, crop rotation, conservation agriculture, cropping system, maize