Chapter 6
Fertilizer use by crop

In Egypt, mineral fertilizers, especially nitrogen, phosphate and potash are being applied to an increasing extent. Figure 8 shows that the consumption of nitrogen and phosphate fertilizers has tripled during the last 30 years.

This increase in consumption is due to various factors including:

• The additional cropped area (Figure 9).

• The introduction of new high yielding varieties which need higher rates of fertilizers, as indicated by the increases in recommended rates in Table 7.

• The construction of the High Aswan Dam which reduced the quantity of suspended materials deposited on the soil during floods, which permitted for thousands of years the restoration of the fertility of Egyptian soils.

Source: Taha, 2000.

Source: MALR, 2003.

Apart from mineral fertilizers, organic manures are the main source of plant nutrients, especially of nitrogen and micronutrients.

The recommended rates of N, P₂O₅ and K₂O for all the crops, on a national level, are issued by MALR each year through an annual Ministerial decree (Tables 7 to 12). The rates of fertilizers to be applied to the crops evidently differ according to the species and variety, soil type as well as the area allocated to each crop in that year.

TABLE 7
Recommended rates of fertilization, 2003/04 compared with 1979/80

Source: MALR, 2003.

TABLE 8
Recommended rates of fertilization for other field crops and pulses

Source: MALR, 2003.

TABLE 9
Recommended rates of fertilization for aromatic and medicinal plants

Source: MALR, 2003.

TABLE 10
Recommended rates of fertilization for fodder crops

Source: MALR 2003.

Effectiveness of various sources of nutrients

An important factor influencing the efficient use of fertilizers is the source of the nutrients. In Egypt, studies have been carried out to evaluate the effectiveness of different sources of N, P and K for different field crops.

As regards nitrogen, field experiments carried out on cotton, wheat, maize and rice indicate that calcium nitrate and urea are of nearly equal value. On rice, sulphur coated urea and urea super granules were found to be superior to urea and ammonium sulphate, while iso-butidylin di-urea was the least effective (M.R. Hamissa et al., 1997).

TABLE 11
Recommended rates of fertilization for fruit crops

Source: MALR, 2003.

TABLE 12
Recommended rates of fertilization for vegetable crops

Source: MALR, 2003.

The phosphate fixation process in alkaline soils and the presence of calcium carbonate result in a low recovery of added phosphatic fertilizers. A number of field trials have been carried out to study the effectiveness of phosphate sources on clover, wheat, faba bean, alfalfa and maize. The data obtained revealed that phosphate fertilizers containing phosphorous in water soluble form, such as single superphosphate, triple superphosphate and polyphosphate, were the most effective, followed by those containing phosphorous soluble in ammonium citrate or two percent citric acid, such as dicalcium phosphate and basic slag. Rock phosphate was the least effective source.

Regarding micronutrients, studies on some field crops indicated that the foliar application of micronutrients in mineral or chelated forms was more effective than soil application, except in some special cases such as the application of zinc sulphate or zinc oxide on rice.

To assess the effectiveness of organic manures, a series of field trials were conducted in two successive seasons to study the fertilizer value per unit of nitrogen in pigeon refuse, FYM, green manure and two kinds of compost (one prepared from rice straw and the other from faba bean straw). Rice was cultivated in the first year followed by cotton and wheat followed by rice in the second year (Taha, 2000).

The results obtained (Table 13) showed that organic manures increased rice and wheat yields directly. Pigeon refuse gave the highest values, while compost and FYM resulted in the lowest values. As regards the residual effect, pigeon refuse, FYM and composted bean straw had almost the same effect on rice, while composted rice straw showed superiority over the others on the cotton crop.

TABLE 13
Direct and residual effect of organic manures

Crop productivity could be increased on both old land and in the newly reclaimed areas by means of improved varieties, optimum cultivation practices, high quality seed and the efficient use of land and water inputs. In addition, with better extension, the gaps between yields obtained by farmers and those obtained by researchers could be narrowed or even closed.