Nutrient Use Efficiency:
Nutrient Use Efficiency is defined as the amount dry matter produced per unit of nutrient applied or absorbed.
Classification of NUE:
1. Agronomic efficiency: it is defined as the economic production obtained unit of nutrient applied.
2. Physiological efficiency: it is defined as the biological production obtained unit of nutrient applied.
3. Apparent recovery efficiency: it is defined as the quantity of nutrients absorbed per unit of nutrient applied.
Time of fertilizer application
PRIOR TO SOWING: Some of water insoluble fertilizers such as rock phosphate and basic slag are applied 2 to 4 weeks before sowing to enable conversion water insoluble form to soluble form for efficient crop utilization. In soils, when lime requirement is 2ton or less, the entire amount should apply at one month before sowing of the crop.
AT SOWING: Application of fertilizer at the time of sowing or just before sowing is called basal application. A part of recommended nitrogen and entire quantity of phosphate and
potassium fertilizers are applied as basal.
After sowing the crop: Application of fertilizers after the crop establishment is called top dressing. Depending on the stage of crop, generally a portion of nitrogen is applied as top
Split application: When fertilizer is applied at two or more deferent time, the system is called a split application. For long duration crops, N must be applied in two or three split
Method of fertilizer application
A. Soil Application
Broadcasting: Application of fertilizer uniformly on the soil surface is known as broadcasting of fertilizer. This is done either before sowing of the crop or in the standing crop (top dressing). Broadcasting is the most widely practiced method in India due to
ease in application.
Band Placement: Application of fertilizers in narrow bands beneath and by the side of the crop rows is known as band placement of fertilizers. Band placement is done under the
following situations: (I) when the crop needs initial good start, (2) when soil fertility is low, (3) when fertilizer materials react with soil constituents leading to fixation, and (4) where volatilization losses are high. Depending on the root system, fertilizer band is placed
directly beneath the seed or by the side of the row. For crops like castor, red gram, cotton etc., with tap root system, fertilizer band can be 5 cm below the seed. In cereals and millets, which produce fibrous root system, it is advantageous to place fertilizers 5 cm
away from the seed row and 5 cm deeper than the seed placement.
Point Placement: Placement of fertilizers near the plant either in a hole or in a depression followed by closing or covering with soil is known as point placement of fertilizers.
Fertigation: Application of fertilizers with irrigation water is known as fertigation. This saves the application cost and allows the utilization of relatively inexpensive water soluble fertilizers. Usually nitrogenous fertilizers are most commonly applied through irrigation water. It is generally followed with drip irrigation.
Application to plant
Root Dipping: The roots of the seedlings are dipped in nutrient solution before transplanting. In soils deficient in phosphorus, roots of rice seedlings are dipped in phosphorus slurry before planting.
Foliar application: Application of fertilizers to foliage of the crop as spray solution is known as foliar spray of fertilizers. It is also called non- root feeding. These solutions may be prepared in a low concentration to apply any one of plant nutrient or a combination
of nutrients. This method is suitable for application of small quantities of fertilizers, especially micronutrients.
FUE (Fertilizer Use Efficiency): It may be defined as yield per unit fertilizer input or it may be fresh weight or product yield per unit content of nutrient. Nutrient use efficiency of different nutrients Nutrient Efficiency Cause of low efficiency Nitrogen 30-50 % Immobilization, volatilization, de-nitrification, Leaching Phosphorus 15-20% Fixation in soils Al – P, Fe – P, Ca – P Potassium 70-80% Fixation in clay – lattices Sulphur 8-10%
Immobilization, Leaching with water Micro-nutrients (Zn, Fe, Cu,Mn, B) 1-2% Fixation in soils
Factors affecting NUE
1. Leaching (NO3).
2. Gaseous Losses (NH3,N2O,N2).
3. Immobilization by chemical precipitation, adsorption on exchange complex and microbial cells.
4. Chemical reactions between various components in fertilizers during mixing, before application to soil.
5. Physical properties of soil.
6. Chemical properties of soil.
7. Fertilizer characteristics.
Methods of Increasing Fertilizer Use Efficiency
• Following methods which can be adopted to increase FUE:
• Agronomic methods
• Chemical methods
1. Agronomic methods:
I. Application of fertilizers at right time with required quantity The phosphates in general are more efficient when the entire dose applied as basal dressing, potash entire quantity as basal dressing or part as basal and rest in split doses depending on the soil texture
and the nitrogen in 2-3 (or 4) split doses.
Example: • In Sugarcane, Potassium application normally done along with N application because of better utilization of N, in the presence of K. therefore K is applied at 45, 90 DAS.
2. Chemical methods: Synthetic or chemical fertilizers should be good quality and right source for crops. Examples:
• Oilseed- Generally Sulphate fertilizers like elemental sulphur @25Kg/ha, ZnSO4 @ 25 Kg/ha, Borax @ 1-2% application must be done.
• In tobacco plant avoid using of fertilizers containing chlorine for preventing from scorching effect.
• In tea plantation use of (NH) 2SO4 is best.
• In Paddy, Ammonium and urea fertilizer are more efficient for paddy under different Indian conditions than nitrate fertilizers.