These replacement and/or supplementary supplies can be provided through organic manures and/or mineral fertilizers. This publication concerns the provision of raw mate- rials for two important mineral fertilizers, phosphate and potash. Three major nutrients are required in large quantities for plant growth, nitrogen, phosphorous and potassi- um. Three secondary nutrients are required in smaller quantities on some soils; sulfur, calcium and magne- sium. Seven micronutrients may be required in small amounts where deficient. Each nutrient has a specific biological function and, while there may be synergies between the nutrients, none has a substitute
