Fertilization replenishment

Sanchez, P.A. and B.A. Jama (2002) Soil fertility replenishment takes off in East and Southern Africa.- In Vanlauwe, B et al. (eds) (2002) Integrated plant nutrient management in Sub-Saharan Africa.- Pp. 23-45. CAB International, Wallingford, UK. 

Fertilizer Use. The worldwide use of fertilizers has an important, positive effect on the environment. Conservative estimates (112) iadicate that about 30% of world food production is direcdy attributable to fertilizer use. Without fertilizer, therefore, at least 30% mote virgin land would have to be devoted to agriculture, and 30% more labor and other resources would have to be expended. Even more serious would be the effects of land tillage and cropping without nutrient replenishment. Past experience has shown that, under such a condition, crop yields progressively decrease, the land eventually becomes barren, and forces of wiad and water erosion prevail. 

Fertilizers are immensely important to humanity. Agriculture requires fertilizers because growing plants remove various chemical elements from the soil. In a fully contained ecosystem, decaying organic matter replenishes the soil, but the elements contained in crops that are harvested and shipped elsewhere are not replenished. Thus, intensive agriculture inevitably depletes the soil of essential elements, which must be replaced by fertilization. 

Fertilization using animal products has been practiced since ancient times. Animal manure returns nutrients to the soil, replenishing elements that are depleted as crops are grown and harvested. It is likely that the use of animal fertilizers quickly followed the domestication of goats, sheep, and cattle. 

Fertilization is carried out to replenish soils and to maintain desirable pH levels. Nitrogen is usually applied in an acidic form. Minor element requirements have been studied. Copper availability is important, as it affects leaf processing, as will be shown later. 

Plants consume nitrogen compounds present in the soil, and if growth is to continue, these compounds must be replenished, as by the addition of fertilizers. Until relatively recently, the fertilizer used for thi purpose consisted chiefly of animal wastes. Now chemists have learned to convert atmospheric nitrogen into fertilizer compounds by artificial methods. 

ICRAF (1996) Replenishing soil fertility through improved sesbania fallows and phosphorus fertilization, International Centre for Research in Agroforestry, ICRAF Annual Report, 147-152... 

Buresh, R.J., Smithson, P.C. and Heliums, D.T. 1997. Building soil phosphorus capital in Africa. In Buresh, R.J., Sanchez, P.A. and Calhoun, F. (eds) Replenishing Soil Fertility in Africa. Soil Science Society of America/American Society of Agronomy, Madison, pp. 111-149. 

Bekunda, M.A. Bationo, A. and H. Ssali (1997) Soil fertility management in Africa, a review of selected research trials.- In Buresh, R.J, et al. (eds) (1997) Replenishing soil fertility in Africa.- Soil Science Society of America, Madison, USA. Pp. 63-79. 

To maintain soil fertility and productivity and prevent land degradation, nutrients taken up by crops must be replenished through the application of fertilizers. The use of fertilizer results in many benefits to producers, consumers, and the environment, starting with... 

The nutrients that the plants take from the soil to grow and produce fruit need to be replaced by replenishing the soil and by the application of fertilizers. The nutrient uptake of an apple orchard in full production is relatively low. If the yield is between 25 and 50 t/ha, the trees take up 20-30 kg N, 5-15 kg P2O5, 50-80 kg K2O, 17-20 kg CaO and 6-8 kg MgO (Greenham, 1980). The nutrients supplied by fertilizers are not fully available for use by the fruit plants, as nutrients may be lost as a result of leaching, runoff and fixation. On the other hand, nutrients are constantly being made available to the plants through mineralization and the action of weather on the soil. 

The fertilizer industry is based on replenishing the primary nutrients (i.e., nitrogen, phosphorus, and potassium). Commercially, fertilizers are produced in three different forms which are single nutrient, binutrient, and multinutrient. 

Potassium is essential to plant growth. Approximately 95% of mined potassium is used to manufacture the fertilizer potassium nitrate (KNOs). Potassium is also found in soil, where it is continuously replenished through decaying plants and animal waste. 

However, whenever soil is plowed, the nutrient-replenishing process is disrupted and the potassium is lost. This is why it becomes necessary to add fertilizer to soil. 

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