A study to assess the effect of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L.) within the same basin or outside the basin on root length density (RLD) was conducted at the International Crop Research Institute for Semi-Arid Tropics (ICRISAT) Matopos Research Station from December 2009 to April 2010. The experiment was laid out in a Randomised Complete Block Design (RCBD) with four treatments replicated four times namely; sole maize, sole cowpea, maizecowpea intercrop with cowpea and maize planted within the same basin and maize-cowpea intercrop with cowpea planted 20 cm outside the maize basin. There was significant difference (P < 0.001) in RLD, grain yield and stover yield. Maize-cowpea intercropped within the same basin achieved higher RLD, grain yield and stover yield than cowpea that was intercropped outside the basin and the sole crops. The land equivalent ratio (LER) in both intercrop designs showed that intercropping had better grain yield performance when compared to sole cropping. It can be concluded that intercropping maize and cowpeas within the same basin can result in an environment around the crop achieving higher RLD which translates to better grain yield compared to the sole cropping and intercropping cowpeas outside the basin.

The potential of different water hyacinth compost application rates in influencing growth attributes, yield and heavy metal accumulation of lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) in tomato fruit was studied in Masvingo. Four treatments of water hyacinth compost rates of 0, 37, 55.6 and 74.1 t·ha −1 were each replicated three times and applied in a randomized complete block design set up. Results showed that water hyacinth compost application rates significantly affected plant height, days to maturity and yield but had no influence on the number of tomato fruits per plant. The plant height at application rate of 74.1 t·ha −1 was 25%, 56% and 63% higher than the control at week 6, 9 and 12, respectively. At application rates of 56.6 t·ha −1 , plant heights were 11%, 13% and 12% higher than the control whilst marginal plant height differences of −4%, 6% and 4% were recorded between application rate of 34.7 t·ha −1 and the control at week 6, 9 and 12, respectively. Tomato plants under compost rates of 34.7, 56.6 and 74.1 t·ha −1 in comparison to the control delayed maturity by 10, 17 and 20 days, respectively. Yields of 52, 55, 60 and 68 t·ha −1 were realized from hyacinth compost rates of 0, 34.7, 56.6 and 74.1 t·ha −1 , respectively. Heavy metal concentrations increased with increase in the water hyacinth compost rate but at all application rates, the average concentrations were 85%, 93% and 86% lower than the Codex Alimentarious Com-* Corresponding author. M. Mashavira et al. 546mission permissible levels for Pb, Cu and Zn. Water hyacinth compost at a rate of 74 t·ha −1 therefore can be used for increased tomato yield without exposing consumers to heavy metal toxicity.

Sweet wormwood (Artemisia annua L.) is a highly valued crop, native to China, whose active ingredient "artemisinin" and its derivatives: artemether and artesunate, are used to prepare anti-malaria drugs. In Zimbabwe, very little has been done on improving agronomic practices that can enhance the yield of this crop. As a result, herbal gardens in Zimbabwe producing this sweet aromatic herb are realizing low leaf biomass. The objective of this study was to determine the effects of varying nitrogen fertilizer levels on growth and yield of Artemisia annua. A randomized complete block design (RCBD) was used and replicated four times. The fertilizer treatments consisted of 0, 40 kg N/ha, 80 kg N/ha, 120 kg N/ha, 160 kg N/ha and were applied as a top dress four weeks after planting. Applying 80 kg N/ha, 120 kg N/ha or 160 kg N/ha resulted in the best performance of Artemisia annua with respect to the plant height, root dry weight, stem dry weight and leaf biomass. Low N level (40 kg N/ha) recorded significantly low means in plant height, root weight, stem weight and leaf biomass. The results suggest that 80 kg N/ha should be recommended for use by Artemisia annua farmers, since there was no significant different among the three higher fertilizer levels. However there is need for further research to determine different fertilizer use efficient to come up with accurate agronomic data package for Zimbabwean farmers.