Fertilizers use by crop in Pakistan
Fertilizer recommendations for different crops are prepared by provincial research institutes and released for information to the agriculture extension services for dissemination to the farming community. Federal institutes (PARC, NFDC) and the fertilizer industry also compile information of this kind and publish it for the farmers. NFDC, under an FAO project, developed a methodology for interpreting crop responses to fertilizers, economic analysis and calibration with soil analysis. The general recommendations issued by government departments are given in Table 4.
The general recommendations are mostly given as a range, low for fertile soils and higher rates for fields with poor soil fertility. The previous crop, soil texture, source of irrigation and rainfall are also taken into consideration. There is a network of over 60 soil testing laboratories in both the public and private sectors to provide recommendations based on soil analysis for specific soils and crops.
The amount of fertilizer that should be applied depends on the crop to be sown, the previous crop, the organic manures that will be applied, the crop variety, the input/output price ratio, yield potential and management level. The use of site specific recommendations by farmers is negligible. Farmers apply fertilizers according to their financial resources, the availability of water, the types of fertilizers available and the expected financial returns.
All phosphorus and potassium and half of the nitrogen is broadcast and incorporated in the soil before sowing.
Phosphorus can be applied at the first irrigation if this was not done at sowing.
The remaining half of the nitrogen is top dressed with the first or second irrigation.
On light textured soils, nitrogen should be applied in three splits.
In rainfed areas all fertilizer could be applied at sowing.
In the case of late planting, it is better to apply all the fertilizers at sowing and slightly increase the dose.
Potassium, zinc (Zn) and other micronutrients should be applied where needed based on the results of soil analysis.
Application of zinc sulphate (35 percent Zn) at the rate of 12.5 kg/ha after 7-10 days of transplanting.
All P2O5 and K2O and half of the N are to be applied before transplanting. Nitrogen fertilizer should not be applied in standing water to avoid volatilization losses; it should be incorporated in the mud. Basal urea incorporated into the mud and later top dressed in the wet soil followed by flooding can increase the yield by 25-30 percent compared with the same amount of urea applied by the common method i.e. fertilizer application in standing water.
The remaining half of the N is applied at the panicle initiation stage i.e. 35 to 40 days after transplanting, in dry soil followed by flood irrigation.
Nitrogen fertilizers containing nitrogen in ammoniacal form (urea, ammonium sulphate) are more beneficial for rice.
Potassium fertilizer should be applied based on soil analysis.
All P2O5, K2O and 1/3 of the N should be applied at sowing by band placement.
Then 1/3 of the N should be applied with the first irrigation and the remaining 1/3 of the N at the pre-flowering stage.
If phosphate was not applied at sowing, it should be top dressed along the lines before the first irrigation.
In case the wheat crop is fully fertilized with phosphorus and the soil test value is above 10.0 mg/kg, then P2O5 application to cotton can be reduced.
Potassium and micronutrients (boron) should be applied on the basis of soil analysis. Boron is important for cotton, but one has to be careful because the difference between deficiency and toxicity is very narrow.
All phosphorus, potassium and 1/3 of the N should be applied at planting time in the furrows below the seed sets. Fertilizer contact with the seed sets has to be avoided.
The remaining 2/3 of the N should be applied in two splits, i.e. 1/3 in April and 1/3 in May.
Twenty to 25 cart loads of farm yard manure (FYM) per hectare are also recommended to be applied at the time of soil preparation at least one month before planting.
For the ratoon crop about 30 percent more fertilizer are required than for the newly planted sugar cane. N should be applied in two splits, i.e. half along with P2O5 and K2O at the time of sprouting and the remaining half two months after the first dose.
Most of the recommendations for citrus fruits, deciduous fruits and mango are on a per plant basis. After planting the fruit tree, the application in the first year on average is 150 g N, 50 g P2O5 and 50 g K2O, mixed with 10-15 kg of well decomposed FYM for every plant. The dose in g is incrementally increased every year by about 75 g for N, 50 g for P2O5 and 25 g for K2O. Thus a mature plant of about 10 years will receive 1.5 kg N, 0.5 kg P2O5 and 0.5 kg K2O, mixed well with about 50 kg well decomposed FYM. Micronutrients are also to be added.