Best management practices for safe and economic use of Nitrogenous fertilizers

K.Venkatesh, S.K.Singh, H.M.Mamrutha, V.Tiwari, O.P.Gupta, and I. Sharma

Indian agriculture has witnessed a tremendous fourfold increase in food production over the past three decades. This enhanced food grain production later known as ‘green revolution’ could be mainly attributed to the introduction of high-yielding, input responsive cultivars of wheat and rice in the mid-1960s and to the increased availability and use of chemical fertilisers, especially the nitrogenous (N) fertilizers.

Nitrogenous fertilizers supply N which is very essential for plant growth and development and mainly supplied to the crop plants in the form of urea, Diammonium phosphate (DAP) etc. When N fertilizers are used correctly they are very beneficial, but unscientific practices of their usage could lead to large scale pollution and harmful effects on environment. Both surface and groundwater are very vulnerable to No3- contamination by excess use of N fertilizers. Protecting the water bodies in particular and environment in general from No3- contamination is major concern. Therefore here we discuss the best management practices for safe and economic use of Nitrogenous fertilizers.

Always apply fertilizers based on soil nutrient status

Fertilizers should be applied only based on the soil nutrient status, which can be known by testing the soil at a laboratory. Nowadays all state department of agriculture district headquarters are having free soil testing facilities. Proper care should be taken while collecting soil samples.

Always supply recommended dose of fertilizers

Dosage of fertilizer should be as per the dose recommended for the region. These recommendations in India are normally made by State Agricultural Universities, State Departments, crop specific Research Institutes etc.

Table 1. Recommended dose of fertilizers and specific crop growth stages of maximum N demand for split application of N in different crops of India.

 

Crop Fertilizer dose (N:P*:K*) Split Application Stages of Nitrogen Reference
 Rice  150:60:60 Irrigated  
50 % (Basal-Before Transplanting) 25 % (21 DAP) 25 % (Panicle Initiation) DRR, Hyderabad
 60:30:20 Upland or Direct Seeded
0 % (Basal) 50 % (three weeks stage) 25% (40 to 45 DAP) 25% (Panicle Initiation)
 120:60:60 Hybrid Rice  
50 % (Basal-Before Sowing) 25 % (30-35 DAP/Max. Tillering) 25 % (Panicle Initiation/booting)    
Wheat   Irrigated DWR, Karnal
 120:60:40 Medium or Heavy soils
50 % (Basal-Before Sowing) 50 % (Fist Irrigation @ 21 DAS) -
 120:60:40 Light or Sandy soils
50 % (Basal-before Sowing) 25 % (Fist Irrigation @ 21 DAS) 25 % (Heading)
 40:20:00 Rainfed
100 % (Basal-Sowing) - -
Maize 100:75:75 20 % 25 % (4 leaf ) 30 % (8 Leaf ) 20 % (Flowering ) 5 % (Grain Filling) DMR, New Delhi
QPM, Maize 180:80:80 10 % (Basal) 20% (4 leaf) 30% (8 Leaf) 30% (Flowering) 10% (Grain Filling)
Bajra  60:45:40 Irrigated ICRISAT, Hyderabad
50 % (Basal) 25 % (25-30 DAS) 25 % (Ear formation)
  Rainfed
60:45:30 100 % (Basal) - -  
Bengal Gram 25:50:00 100 % (Basal) - - ICRISAT, Hyderabad
Pigeonpea 25:50:00 100 % (Basal) - - ICRISAT, Hyderabad
Cotton   Irrigated  
100:50:50 1/3rd (Basal) 1/3rd (30 Days After Emergence) 1/3rd (60 DAE) CICR, Nagpur
50:25:25 Rainfed
50 % (Basal) 50 % (30 Days After Emergence) -
Sugarcane   Adsali SBI, Coimbatore
 350:170:170 Heavy Soils
100 % P (Basal) 50 % N & 50 % K 50 % N & 50 % K (90DAP)
Light Sandy soils
100 % P (Basal) 1/3rd N & K (45 DAP) 1/3rd N & K (90 DAP) 1/3rd N & K (120 DAP)
 250:115:115 Annual/Seasonal/Eksali
     
Sorghum  80:40:40 Irrigated  
50 % (Basal) 50 % (30 DAS before irrigation)   DSR, Hyderabad
 60:40:40 Rainfed light Soils
100 % (Basal) - -
Groundnut 40:60:40 80 % (Basal) 20 % (30 DAS)   NRCG, Junagad
Soybean 20:80:20:20 (N:P:K:S) 100 % (Basal) - - DSR, Indore
Mustard  90:60:40 Irrigated DRMR, Bhratpur
50 % (Basal) 25 % (pre-bloom stage) 25 % (pod-filling stage)
 50:30:20 Rainfed
100 % (Basal) - -
Sunflower 175:65:48 2/3rd (Basal) 1/3rd (Flowering) - ICRISAT, Hyderabad
Potato   Northern Plains CPRI, Shimla
120-150: 80-100: 80-100 50 % (Basal) 50 % (30 DA planting) -
  Southern plains and Hills
100-120: 100-120: 80-100 50 % (Basal)  50 % (30 DA planting) -
* P and K should always be applied as basal dose*Amount of K applied should be decided based on the soil test data

Selection of suitable fertilizer source

Selection of fertilisers should be done according to the soil reaction viz., acidic fertiliser for alkaline soils and basic fertilisers for acidic soil reactions. Slow-release nitrogen fertilizers coated with nitrification inhibitors and urease inhibitors can be chosen in rice, which will help in reduction of N losses due to leaching. Nitrogen in the form of organic manures is also less prone to short-term loss by leaching. Details of different fertilizers (Major and Micronutrients) available in the market and their % nutrient content is given in table 2 & 3.

Table 2. Fertilizers available in the market and their % nutrient content

S. No. Fertilizer Nutrients as % of product
N P2O5 K2O S MgO
Simple or Strait Fertilizers
Nitrogenous Fertilizers
Ammonia 82.2 - - - -
Urea 46 - - - -
Ammonium nitrate 33.5 - - - -
Calcium ammonium nitrate 26-30 - - - -
Phosphatic fertilisers
Rock Phosphate - 18 - - -
Potassic fertilizers
Potassium chloride (MOP) - - 60 - -
Complex fertilizers
Ammonium sulphate 21 - - 24 -
Ammonium chloride 25 - - - -
Potassium sulphate 50 - - 18 -
Potassium magnesiumsulphate - - 22- 30 17-22 10-11
Single Super Phosphate (SSP) - 16 - 12 -
MAP 11 52 - - -
DAP 46 18 - - -
8 Mono PotassiumPhosphate - 52 34 - -
Potassium Nitrate 13 - 45 - -
10  Urea AmmoniumPhosphate 28 28 - - -
11  Ammonium NitratePhosphate 23 25 - - -
 12 Nitrophosphate 20 12 - - -
13  AmmoniumPhosphateSulphate Nitrate 20 17 - - -
NPK Complex Fertilizers
 1 15-15-15 15 15 15 - -
10-26-26 10 26 26 - -
12-32-16 12 32 26 - -
4 22-22-11 22 22 11 - -
14-35-14 14 35 14 - -
17-17-17 17 17 17 - -
14-28-14 14 28 14 - -
19-19-19 19 19 19 - -
17-17-17 17 17 17 - -
10  20-10-10 20 10 10 - -
Liquid Fertilizers
1 Urea AmmoniumNitrate 32 - - - -
SuperphosphoricAcid - 70 - - -
AmmoniumPolyphosphate 10 34 - - -

Table 3. Micronutrient Fertilisers and their nutrient content

S. No. Fertilizer Element Supplied Nutrients as % of product
 1 Zinc Sulphate Zinc 21.0
Manganese Sulphate Manganese 30.5
Ammonium Molybdate Molybdenum 52.0
Borax Boron 10.5
Solubor Boron 19.0
Copper Sulphate Copper 24.0
Ferrous Sulphate Iron (Fe) 19.5
Chelated Zn Zinc 12.0
Chelated Fe Iron (Fe) 12.0
10  Zinc Sulphate monohydrate Zinc 33.0

Proper method of application

The widely practiced method of fertilizer application in India is by surface application through broadcasting where fertilizers are uniformly distributed over the whole cropped field. Broadcasting is preferred under conditions such as, crops with a dense stand and not sown in rows; for application of readily soluble nitrogenous fertilizers; when high rate of fertilizers are used and in crop plants whose roots spread widely in the soil.  Some of the drawbacks of broadcasting are that it stimulates excess weed growth and fertilizers especially P may come in contact with a large volume of soil and are likely to be fixed and unavailable for crop.

Band application

Band application of fertilizer is done by placing a band of about 3 - 4 cm by the side or below the seed as shown in fig-1. Band application is practiced when a) small quantities of fertilizers are to be supplied; 2) when phosphatic fertilizers are applied in acidic soils 3) where fixation of phosphorus is a problem; 4) in the case of crops sown in wide rows; 5) on soils with low fertility and 6) for application of fertilizers to shallow rooted crop plants.

 Band application of Fertilizers by the side of crop rows

Figure 1. Band application of Fertilizers by the side of crop rows

Fertigation

Recent methods of application like fertigation would help in increasing the nutrient use efficiency along with reducing the losses. Fertigation is a method of fertilizer application in which fertilizer is incorporated within the irrigation water by the drip system. In this system fertilizer solution is distributed evenly in irrigation. The availability of nutrients is very high therefore the efficiency is more. In this method liquid fertilizer as well as water soluble fertilizers are used. By this method, fertilizer use efficiency is increased from 80 to 90 per cent. Practicing fertigation is beneficial to farmers in timely and site specific application of nutrients in addition to reducing quantity of fertilizer to be supplied as nutrients are directly supplied to root zone.

 fertigation system

Figure 2. Layout of fertigation system and photographs showing fertigation/drip irrigation in Potato, Sugarcane and carnation.

Split application of fertilizer N

Split application of N to meet the immediate crop growth stage specific N needs is recommended for maximum N use efficiency with reduced losses. Splitting the total N into two doses, half as basal dose and rest as top-dressing in case of heavy soil types is recommended. In case of light soils, nitrogen should be applied in three equal splits i.e 1/3 as basal, 1/3 after 30 days of sowing and the balance 1/3 about 50-60 days after sowing. Finally splitting should be crop specific and crop stage specific to match the growth stage specific N demand. To know these specific crop growth stages of maximum N demand leaf colour chart can be useful. The leaf colour chart (LCC) primarily developed for rice, is a tool to rapidly assess leaf N status and thereby guide the application of fertilizer N to maintain optimal leaf N content, which is vital for achieving higher yields. A detail of specific crop growth stages along with the amount of recommended N to be supplied as split dose in different crops is given in table 1.

In addition to above practices some of the following measures can be adopted for economic and safe use of fertilizers

  • For at least a week, flooding with too deep water or poor drainage should be avoided after application of the fertilisers.
  • Top dressing should be done after draining out the water and weeding so that the loss of nutrient is minimum. Paddy fields, used for transplanting, should be puddled and fertilisers should be applied at the time of puddling. This will help fertilisers to penetrate and get stored in the soil.
  • The acidic soils should be treated with liming materials as and when required.
  • Deep placement of fertiliser, along with foliar feeding of nitrogen (i.e., urea) through spraying of nitrogenous fertiliser in place of top dressing should be done in case of dry lands.
  • Addition of organic manures or green manuring should be done at least once in 3-5 years. Weed growth should not be permitted in cropped areas, during any part of the year.
  • In case of flooded fields or calcarious soils, use of slow release nitrogenous fertilisers like sulphur coated urea, urea super granules, neem coated or neem blended ureas should be used so that loss of nitrogen can be minimised.
  • Mud bolls, contain urea and should be used in case of deepwater crops because they help in proper placement and also reduce the loss of nitrogen from the field.
  • Appropriate plant protection measures and proper tillage practices should be adopted so that plants remain healthy and absorb the applied nutrients from the field.

Authors:

Venkatesh K.*1, Singh S.K.1, Mamrutha HM1, Tiwari V.1, Gupta O.P.2, and Sharma I3

1Division of Crop Improvement, 2Division of Quality and Basic Sciences, 3TheProject Director, Directorate of Wheat Research, Karnal-132 001, Haryana-India

*Corresponding author email: This email address is being protected from spambots. You need JavaScript enabled to view it.