Monday, Apr 27, 2026 11:00 [IST]
Last Update: Monday, Apr 27, 2026 05:20 [IST]
Awareness and
interest in improved Nutrient Use Efficiency (NUE) has never been greater.
Driven by a growing public belief that crop nutrients are excessive in the
environment and farmer concerns about rising fertilizer prices, energy crisis
and stagnant crop prices, the fertilizer industry is under increasing pressure
to improve nutrient use efficiency. The mineral nutrients applied but not taken
by the crop are vulnerable to losses from leaching, erosion, denitrification,
volatilization, and temporary fixation. Low nutrient recovery efficiency not
only increases cost of crop production but also causes environmental pollution.
Agronomic
nutrient use efficiency (kg crop yield increase per kg nutrient applied) is the
basis for both economic and environmental efficiency.The use efficiency of Nitrogen
(N) ranges from 20-30% under rainfed conditions and 30-40% under irrigated
conditions, 10-30% for Phosphorous (P), 50-60% for Potassium (K), 8-12% for Sulphur
(S), and hardly 4-5% for the micronutrients. It indicates that, roughly 50% of nitrogen
and 90% of phosphorus applied through chemical fertilizers are lost to water
and the atmosphere, which causes water eutrophication, Green House Gases
Emission (GHGE), and other associated environmental issues. Application of
organic manures is recognized as a key strategy for smart farming, because it
optimizes the nutrient use efficiency, by balancing nutrient supply with
crop demand, reducing leaching, and improving soil health.
Optimizing Nutrient Use Efficiency
through Organic Manures
Organic manures are
the natural materials from plants and animal sources that directly and
indirectly affect the soil’s physiochemical and biological properties. A
bio-fertilizer, a misnomer, is also a type of organic carrier that contains
beneficial microbes (algal, fungal, bacteria) that improves plant growth by
mobilizing the soil available nutrients through their biological activities. These
microorganisms enhance nutrient use efficiency (NUE) by fixing atmospheric N,
solubilizing insoluble P and K, production of phytohormones, siderophores, and
improving plant nutrient uptake through enhancement of root architectureand
rhizosphere interactions. Apart from nutrient supply, bio-fertilisers enhance
soil enzymatic activity, increase soil organic carbon, promote soil carbon
stabilizationand restore microbial diversity. Moreover, they contribute to
climate-resilient agriculture by improving plant tolerance to drought,
salinity, and temperature stress, and reducing greenhouse gas (GHG) emissions. Animal
excreta is the greatest source of organic manure around the globe, followed by
poultry and pig manures. Animal manures are a good and sustainable source of
NPK, and the total N excreted in animal manure globally ranges from 81.5
to128.3 Tg per year, though the type and amount of N in animal manure vary significantly.The
fertilizer industry supports the application of nutrients at the right source,
right rate, right time, and in the right place (4R Stewardship) as a best
management practice (BMP) for achieving the optimum nutrient efficiency.
Right source
Organic sources
of nutrients are considered as the most sustainable and environment friendly
than synthetic inorganic fertilizers because they release nutrients slowly;
ensuring a steady supply of nutrients to the plants, reducing the risk of
nutrient wastage, water pollution and harming beneficial soil organisms. In
addition to increasing soil fertility, organic manures improve soil organic carbon (SOC) content,
soil microbial activity for
crucial nutrients recycling, water retention and soil aeration, aggregates
stability,maintain soil pH, and minimize risk of groundwater contamination. Due to their
slow-release nature, organic manures reduce volatilization of nitrogen species, and their
ability to prevent acidification, while increasing
organic matter content of soils, promotes carbon sequestration, further
preventing greenhouse gases emission. Since organic manures are derived mainly
from waste, they are renewable, and do not compete with humans and animals for
food. Organic manures are therefore a
sustainable alternative to inorganic fertilizers.
Most crops are
location and season specific-depending on cultivar, management practices,
climate, etc. Key strategies for enhancing NUE via organic sources include:
Organic Amendments: Compost, animal
manure, de-oiled cakes, and crop residues add nutrients to soil, while
enhancing soil organic matter and microbial activity, which helps nutrient
cycling.
Cover Crops and Rotations: Planting
cover crops, especially legumes, fixes nitrogen and reduces nutrient leaching,
with some holding onto nitrogen that would otherwise be lost.
Precision Application: Utilizing
precision agriculture techniques, such as Variable Rate Technology (VRT),
enables applying organic amendments exactly when and where needed.
Right rate
Adequate and
balanced application of mineral nutrients is one of the most common practices
for improving the efficiency of applied N. Both over- and under-application of
plant nutrients result in reduced nutrient use efficiency or losses in yield
and crop quality. Soil testing is the most powerful tool available for
determining the nutrient supplying capacity of the soil, thereby enabling the
farmers to make appropriate decision on right rate of nutrient application,
through organic manures. Unfortunately, soil testing is not available in all
regions because reliable laboratories using methodology appropriate to local
soils and crops are inaccessible or calibration data relevant to current
cropping systems and yields are lacking.
Right time
Greater synchrony
between crop demand and nutrient supply, is highly necessary to improve the nutrient
use efficiency, especially for N. Split application of N during the growing
season is effective in increasing N use efficiency. Tissue testing is a well-known
method to assess N status of growing crops, but other diagnostic tools are also
available. Chlorophyll meters are useful in fine-tuning in-season-N management
and Leaf Colour Charts (LCC) have been highly successful in guiding split N
applications in rice and maize. Precision farming technologies have introduced,
and now commercialized, on-the-go-N sensors that can be coupled with variable
rate fertilizer applicators to automatically correct crop N deficiencies on a
site-specific basis. Use of N stabilizers and controlled release fertilizerssynchronize
the release of N with crop need. Similarly, nitrogen stabilizers {Nitrapyrin,
DCD (dicyandiamide], NBPT[N-(n-butyl) thiophosphorictriamide]} inhibit the nitrification
or urease activity, thereby slowing the conversion of the applied nitrogen
forms into nitrate. The most promising coated-fertilizers like neem coated urea
(NCU), sulphur coated urea (SCU) and lac coated
urea (LCU) are the slow releasefertilizers that release the nitrogen in a
controlled manner, thus enhance the nutrient use efficiency.
Right place
Application
method has always been critical in increasing nutrient use efficiency. Numerous
placements are available, but most of these involve surface or sub-surface
applications before or after planting. Prior to planting, nutrients can be
broadcast, applied as a band on the surface, or applied as a subsurface band,
usually 5 to 20 cm deep. At planting, nutrients can be banded with the seed,
below the seed, or below and to the side of the seed. The recommended dose of
phosphorus must be applied through basal application, preferably in root zone
at planting. After planting, the application is usually restricted to N, and in
some cases for K. Placement can be as a top-dress or a subsurface side-dress.
In general, nutrient recovery efficiency tends to be higher with banded
applications because less contact with the soil lessens the opportunity for
nutrient loss due to leaching or fixation reactions. Placement decisions depend
on the crop and soil conditions, which interact to influence the nutrient
uptake and availability.
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