The fertilizer refers to the substance which provides one or more nutrients necessary for plant growth and development. Fertilizers play a significant role in the modern crop production. They are key inputs contributing about 30 to 70 per cent increase in crop yield. Besides increasing yield per unit area, fertilizers improve the nutritional and storage quality of many crops particularly of the grains, fruit and vegetable crops. This is because fertilizers increase plant resistance to certain diseases, insects, and weather injury. Fertilizers are used in intensive farming to supplement the soil supply of the essential plant nutrients. There are different types of fertilizers but commonly used ones are discussed here.
NITROGENOUS FERTILIZERS: These fertilizers are applied in larger amount than any other fertilizer because nitrogen is required by plants in larger amounts than any other nutrient. Nitrogenous fertilizers play an important role in leaf enlargement and thickness, branching or tillering, flowering, fruit setting, root development and expansion. Deficiency of nitrogenous fertilizers cause stunted growth, delayed maturity, pale, yellow or green colours and roots become thinner and reddish brown. Excessive applications of nitrogenous fertilizers lead to more vegetative growth, lodging and also decreases the availability of other nutrients.
Phosphatic fertilizers are required in a lesser quantity as compared to nitrogenous fertilizers. These contribute to improve yield and quality of crops, strength of cereal straw and thus help to prevent lodging in cereals. These also increase crop resistance to diseases, rhizobial activity and thus nitrogen fixation. Reducing the application of these fertilizers cause stunted growth, purple or reddish leaves, stems, branches and less number of tillers. Low yield and poor quality of crops are often observed in case of inadequate supply of phosphorus fertilizers.
Potash fertilizers are rarely used by the farmers in our country because our soils are less deficient in potash. Positive responses of these are observed in our country that the application of potash fertilizers is more profitable and economical than doubling the rate of nitrogenous fertilizers. Plants absorb large quantities of potash to maintain normal growth and maximum yield. It improves the keeping quality of fruits and vegetables, and the nutritional value of grain crops. Reducing the amount of these fertilizers causes low growth rate, spotted, pale and curled leaves, weak root system and drying of leaves.
Fertilizer use efficiency:
Fertilizer is a costly input. It must be used sensibly to gain much higher yield per unit quantity of nutrients. This will compensate the farmers for the extra cost of fertilizers. Fertilizer use efficiency is an index of extra gain in yield by the effective utilization of fertilizers.
Fertilizer use efficiency can be increased by following measures:-
Selection of fertilizer
Application of correct quantity of fertilizer
Application at proper time
Proper method of application
SELECTION OF FERTILIZER:
Proper selection of fertilizer should be made on the basis of type of the soil and growth stage of the crop. While selecting a fertilizer, its quality and type of formulation (like granular or powder form) must also be considered. If the various sources of same nutrient have same price then cheaper source should be selected.
APPLICATION OF CORRECT QUANTITY OF FERTILIZER:
After selection of the suitable fertilizers, their application rates need consideration that the optimum quantities of nutrients should be applied to each crop. The recommended dose should be economical. In our country most of the farmers use nitrogenous fertilizers and ignore other fertilizers such as phosphatic and potash fertilizers. This imbalanced use is one of the major factors of yield reduction of our crops. So the balanced fertilization should be done to get maximum yield.
APPLICATION AT PROPER TIME:
The time of fertilizer application depends on the type of crop, kind of nutrient, soil and moisture conditions. Fertilizers are usually applied at the time of sowing in case of 1). Short duration and fast growing crops, 2). Rabi crops in barani areas, and 3). Rabi pulses, which require low nitrogen dose. For long duration crops like; sugarcane nitrogen is applied in two or three splits. For vegetable crops in which produce is harvested in many pickings; N fertilizer is usually applied in 2 to 3 splits.
For many crops both P and K fertilizers are mostly applied at the time of sowing; While N is splitted into 2 or 3 doses. The first dose is applied at the time of sowing with P and K application. However, in barani areas all NPK should be applied at the time of sowing.
PROPER METHOD OF APPLICATION:
Applying fertilizers at proper place is as important as applying the correct amount at the right time. A good method of application will distribute fertilizer at a place from where plant roots can take up it easily. The methods of fertilizer application are broadcasting, placement, top-dressing, foliar application and fertigation. The method of application depends on type of crop, stage of crop and available farmer resources.
Fertilizers are most important inputs because these provide essential nutrients for plant growth. Efficient use of fertilizers is a basis component to obtain maximum yield. The efficiency of fertilizer can be increased by the proper selection of fertilizer, by applying required quantity of fertilizer, proper time of application and by using efficient method of application. By adopting these measures and by balanced use of fertilizers we can improve our crop yield.
The writers are associated with the Department of Agronomy, University of Agriculture, Faisalabad, Pakistan. They can be reached at <email@example.com>