Micronutrient needs of tropical food crops

The trace element requirements of tropical crops are reviewed with special reference to their role, the differences between crop species, the differences between cultivars, paths of trace element uptake, effects of climate, the importance of crop management and yield levels

Establishment of an effective endomycorrhizal association on cassava in flowing solution culture and its effects on phosphorus nutrition

Eight cassava (Manihot esculenta) cultivars were grown with or without mycorrhizal inoculation in flowing solution cultures containing approximately 0.1, 1, 10 or 100 ?M phosphate. Rice (Oryza sativa), maize (Zea mays), cowpea (Vigna unguiculata) and French bean (Phaseolus vulgaris) were included in the experiment for comparative purposes. Cassava required a higher external phosphorus concentration for maximum yield (? 10 ?M) than the other species (? 1 ?M) regardless of the inoculation treatments. Roots of inoculated cassava plants were heavily infected with VA endophytes at 0.1 and 1 ?M phosphate, but not at 10 or 100 ?M. Non-inoculated cassava plants were free of infection, and no infections were observed in any treatment on the other species. At 1 ?M phosphate, infection of cassava roots was associated with large increases in whole plant dry wt, concentration of phosphorous in tops and roots, and total phosphorus uptake. At 0.1 ?M phosphate there were also substantial increases in phosphorus concentration in tops and roots but the infected cassava plants were still severely phosphorus deficient and growth was not improved. The results are discussed in relation to the present state of knowledge about the phosphorus nutrition of cassava

Application of the flowing solution culture techniques to studies involving mycorrhizas

A technique to study mycorrhizal effects on growth and P-uptake of cassava (Manihot escultenta, Crantz) grown in flowing solution culture is described. Phosphorus concentrations were carefully maintained constant at 0.1, 1, 10 and 100 ?M by daily analyses and adjustment of the nutrient solutions. Inoculation with mycorrhizal roots hada positiveeffect on P content of plant tissue and/or plant growth only at the two lowest P-concentrations in soulution. These concentrations are two to three orders of magnitude lower than those normally used in conventional nutrient solution cultures