Fertilizer use recommendations are based on experiments carried out by the Ministry of Agriculture. The rates recommended by the Ministry of Agriculture are averages, not tailored to specific crop needs in a specific area. In practice, neighbouring farmers use different rates of fertilizers for the same crop.
An estimation of the fertilizer requirements of the country is crucial not only for the development of agriculture but also to permit correct investment decisions in the fertilizer manufacturing industry. Incorrect forecasts might result either in shortages for the farmer or in excess capacity and low profits for the producers.
Two main factors are taken as a basis for estimating the fertilizer requirements for the country. The first factor is the "indicative cropping pattern" i.e. the optimum rotation, and the area allocated to each crop. The second is the economic optimum rate of fertilizer for each crop under different agroclimatic conditions. In addition to these two main factors, the following factors are taken into consideration:
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FIGURE 5
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Source: MALR, 2003.
In the agricultural year 2002/03, the crop areas in the old and new lands amounted to 5.1 and 1.4 million ha respectively. According to the "indicative cropping pattern", the area allocated to various crops and the recommended rates of nitrogen and phosphate fertilizers, it is estimated that the country needs 1.1 million tonnes of N and 364 thousand tonnes of P2O5.
The status of potash and the micronutrients in most Egyptian soils is different from that of N and P. In consequence, it has been decided to determine requirements for these nutrients by taking the consumption of the previous year and increasing it by about 10 percent. Most farmers have a poor knowledge of potash and micronutrient requirements and it is hoped that, with the help of the extension staff, farmers will recognize their importance. Figures 5 and 6 show the estimates of the areas and fertilizer requirements of "new" and "old" land respectively up to 2017.
It is necessary to distinguish between two expressions:
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FIGURE 6
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Source: MALR, 2003.
Nutrient removal is the amount of a nutrient removed from the field (soil) by a given yield.
Nutrient uptake is the maximum amount taken up by a plant during the vegetative period. Normally uptake is higher than the removal.
The nutrient balance has two different aspects, as follows:
Output (removal from the field).
The balance between the nutrient requirement of the crop to be supplied as fertilizers and the availability of the nutrient from all natural sources (El-Fouly, 1998).
Thus, the input of nutrients from different sources, such as soil, air, water and other sources, including organic manures, should be equal to the amount removed or taken up by the crop. If the quantities from these sources are not sufficient for the crop to reach the target yield, the difference should be added as fertilizer. Insufficient amounts of nutrients result in loss of yield. Excessive amounts represent a waste of resources, possibly a decrease of yield and could be an environmental hazard, as in the case of nitrogen, for example (Fawzi, 1992). In this context:
The fertilizer nutrient requirement = output minus input from natural and organic sources.
Fertilizer requirement = nutrient requirement adjusted for the nutrient content of the fertilizer.
Figure 7 illustrates the steps to be taken to determine the fertilizer requirements.
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FIGURE 7
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