Improving Soil Zinc Biovailability in Response to Crop Residues and Wheat Zn Efficient Genotype – Vajiheh Dorostkar Zinc is an important nutrient in the human diet. It is also an important plant micronutrient. Approximately, 50% of land under cereal cultivation is deficient in zinc. These lands are generally located in arid areas. In Iran, where the study was conducted, around 80% of the cultivated land is zinc deficient. Most crop residues are burned or grazed by animals, but residues balance pH, produce organic matter, and improve C:N, etc. As a result, these residues can be used to improve zinc bioavailability in the soil. Crop residues and wheat cultivars were studied to examine their contribution to soil zinc bioavailability in the soil. Sunflower, clover, bean, sorghum and safflower were used in study. The study showed that the use of crop residues from all of the crops have the potential to enhance the zinc bioavailability in arid Iranian agricultural systems. Vajiheh Dorostka gives her presentation on zinc bioavailability and crop residues in Iran Consequences of Sequential Leaf Harvest on Root Yield and N Export of Two Cassava Cultivars in South-central Cameroon – Jelle Willem Duindam This study was done in collaboration with the International Institute for Tropical Agriculture in Camaroon. The research was important as cassava is commonly studied as a root crop, not a vegetable crop. Leaf harvest of cassava is generally carried out in moist growing regions. It is consumed as a leafy vegetable on a daily basis. The shoot tips of cassava leaves are rich in protein and vitamins, and are harvested because they are more tender than a fully developed leaf. However, cassava leaves need cooking in order to detoxify cyanogenic-compounds. The study examined the effect of different harvesting techniques on root yield, as well as the consequences that harvesting has on nutrient export. The research concluded that cassava root yield drops fast as a result of leaf harvesting (local and improved varieties had equal response). Additionally, it was found that nitrogen exports increased significantly by frequent leaf harvest. The researcher recommends that nitrogen-fixing crops should be grown in a crop rotation with cassava and farmers should select varieties based on tolerance to frequent leaf removal.