The review is an attempt to specify particular features of the biological processes involved in the nitrogen cycle as they occur in the following categories of West African ecosystems : flooded rice .fields, rain-fed agroecosystems, and forests. In rice fields in Senegal the nitrogen input through blue-green algae was reported to be in the range -, of 1-30 kg ha-' yr-'. Figures for heterotrophi...

Although iron (Fe) is the fourth most abundant element in the Earth’s crust and upper mantle (lithosphere), Fe deficiency is among the most common plant micronutrient deficiencies. There are multiple contributing factors, but the most important for practical purposes in California orchard crops are those soil and water characteristics that cause lime-induced Fe chlorosis: soil and water with hi...