India testing procedures to determine N availability, switching

India
is the seventh largest country by area having second largest population in the
world. Our cultivated land is limited while our population is growing at
enormous rate. After independence the number of persons, supported by each
hectare of cultivable land has increased by three times but the Per hectare
productivity is more or less constant.

          Increase needs for enhanced crop
productivity due to ever increasing population necessitated the breeding of
high yielding verities of crops which require high amount for nutrition Increase
in agricultural productivity is required to meet the growing demand of
agri-produce. It could be increased by the use of fertilizers and pesticides.
However, there is currently great concern about the damage caused to the environment
by these compounds. Therefore the development of new strategies for the
implementation of effective and safe agricultural chemicals has become more
important in recent years. This could be achieved in the form of
controlled-release formulation specially based on polysaccharides. These
formulations not only release the active compound in a slow manner but also after
degradation increase the crop output besides proving the water-holding capacity
of the soil. Release systems decrease the amount of active ingredient available
for leaching and volatilization. These formulations will control the
environment, ecosystem and health hazard scaused by the conventional pesticide
formulations. Hence, these polysaccharide based formulations could be utilized
for the safe management of agrochemicals which will decrease their toxic
effects and helpful for their better delivery to the field.

Nitrogen
losses and the impact of those losses on water contamination may be reduced by
improving N fertilizer management and other cultural practices to increase efficient
N use by crop plants.  Management
strategies to reduce soil N loss include improved timing of N fertilizer
applications, better use of soil and plant testing procedures to determine N
availability, switching to use of variable-rate N fertilizer applications and
other more effective N fertilizer application methods, application of nitrification
or urease inhibitors, and use of N fertilizer sources that are suitable for local
environmental conditions (Dinnes et al., 2002). slow release formulations
minimize environmental impact by reducing agrochemical leaching, volatilization
and degradation. For example,50% ofthe encapsulatedinsecticide chlorpyrifos is
released in 5 days, whereas free chlorpyrifos is released in 1 day. (2) Slow
release formulations increase the water-holding capacity of soil. (3) Slow
release formulations better control weeds in the long run. (4) Polymer-clay
formulations store ionic plant nutrients. (5) Polymer hydrogel formulations
reduce compaction, erosion, and water run-off. Agron. Sustain. Dev. (2015) 35:47–66 DOI 10.1007/s13593-014-0263-0

Slow-
or controlled-release fertilizer: A fertilizer containing a plant nutrient in a
form which delays its availability for plant uptake and use after application,
or which extends its availability to the plant significantly longer than a
reference ‘rapidly available nutrient fertilizer’ such as ammonium nitrate or
urea, ammonium phosphate or potassium chloride. Such delay of initial
availability or extended time of continued availability may occur by a variety
of mechanisms. These include controlled water solubility of the material by
semi-permeable coatings, occlusion, protein materials, or other chemical forms,
by slow hydrolysis of water-soluble low molecular weight compounds, or by other
unknown means. Tandan2010

Use
of slow-release N fertilizers to mitigate N losses 

Slow-release
fertilizers (SRF) are being tested for use with agronomic crops as an alternative
to conventional N fertilizers in order to improve NUE and decrease N losses to
the environment.  There are two main
types of slow-release N fertilizers with different modes of action: 1)
condensation products of urea and urea-aldehydes (e.g. urea-formaldehyde,
urea-crotonaldehyde, and urea-isobutyraldehyde based products) and 2) coated
urea fertilizers (e.g. sulfur-coated, polymer-coated, and a mix of sulfur and
polymer-coated urea) (Trenkel, 1997).   

Barbieri
et al. (2006) compared the effects of SRF urea and conventional urea under
no-tillage on corn yields.  Their results
showed no significant differences between fertilizers in neither grain N
content nor NUE, although SRF urea treatments had higher NUE than treatments
with non-coated urea. 

 

Any approach that will increase nutrient
use efficiency (NUE) may lead to a reduction in the amount of applied  fertilizer per unit area. This in turn should contribute
to the reduction of potential pollution problems by decreasing fertilizer
production. One reservation regarding the use of SRF/CRFs forreducing
environmental problems related to fertilizer production is the extent to which
the various materials used for preparing SRF/CRFs (plastics, formaldehydes,
sulphur, etc.) contribute to environmental pollution.One possible way to
improve nutrient and particularly nitrogen use efficiency while reducing the
environmental hazards is by using controlled release or slow release
fertilizers (Hauck, 1985; Shaviv and Mikkelsen, 1993; Peoples et al., 1995; Bockman
and Olfs, 1998; Shaviv, 1999)

 

Nitrogen
use efficiency   

 Nitrogen use efficiency (NUE) is the
proportion of N inputs that are removed in harvested crop biomass, contained in
recycled crop residues, and incorporated into soil organic matter and inorganic
N pools (Cassman et al., 2002).  Nitrogen
use efficiency values of approximately 37% have been reported for cereal crops
in the USA (Cassman et al., 2002) while others have estimated cereal NUE in
developed countries to be approximately 42% with worldwide NUE is approximately
33% (Raun  and Johnson, 1999).  In the last 25 years, NUE has generally
improved in USA corn  systems due to: 1)
better fertilizer management that includes a shift of fall to spring application
and use of split fertilizer applications over the growing season rather than a
single large preplant application; 2) increased yields and better crop growth
as a consequence of greater stress tolerance of hybrids, and 3) conservation
tillage practices and higher plant densities (Cassman et al., 2002). 

nutrient
use efficiency (NUE) can be considered as the amount of nutrients taken up from
the soil by plants and crops within a certain period of time compared with the
amount of nutrients available from the soil or applied during that same period
of time. Improving NUE in agriculture has been a concern for decades
(Dobermann, 2005), and numerous new technologies have been developed in recent
years to achieve this. The types of fertilizers and their management in
agriculture will be at the forefront of measures to improve the global N
balance in the short- and long-term.

Nitrogen
use efficiency is of significant importance in crop production system due to
its impact on farmer economic outcomes and environmental impact. Nitrogen use
efficiency also, may be reduced in crop production due to many factors
including losses of soil nitrogen by volatilization, leaching and
denitification. Jokela and Randall (1989) conducted a study of the effects of N
application rate on residual NO3-N in non-irrigated corn and concluded that
when N rate was increased, soil NO3 -N was also higher.  Another study showed no significant
differences in soil NO3 -N among several N fertilizer rates, although there was
a clear trend of higher soil NO3 -N levels with the highest fertilizer N
application which may cause accumulation in the soil profile and leaching into
groundwater in the long term (Elmi etal., 2005)

Jokela,
W.E. and G.W. Randall. (1989). Corn yield and residual soil nitrate as affected
by time and rate of nitrogen application. Agron. J. 81:720-726.

Elmi,
A.A., T. Astatkie, C. Madramootoo, R. Gordon, and D. Burton. (2005). Assessment
of denitrification gaseous end-products in the soil profile under two water
table management practices using repeated measure analysis. J. Environ. Qual.
34: 446-454

Fertilizers constitute an integral part of improved crop production
technology (Saifullah et al. 2002). Nitrogen (N) is major factor limiting yield
of wheat (Andrews et al. 2004). Optimum N management to wheat is important for
maximum yield, optimum water utilization and minimum contamination to
environment (Corbeels et al. 1999).There is need to reduce use of N fertilizer
application and search for genotypes with greater N use efficiencies, either in
a strict physiological or agronomic sense (Andrews et al. 2004). The efficiency
of wheat cultivars to N use has become increasingly important to allow
reduction in N fertilizer use without decreasing yield. Phosphorus is essential
for enhancing seed maturity and seed development (Ziadi et al. 2008). Both P
and K application favored tillering of wheat and reduced lodging in wheat
(Liakas et al. 2001), improved photosynthetic activity and transport to the
ripening grains. This resulted heavier grains (Zhang et al. 1999). With
adequate application of phosphorus, 20% more grain yield of wheat can be
obtained (Ascher et al. 1994). N and P uptake could be enhanced with increased
P applications (Jiang et al. 2006).). Different
researchers recommended different P application rates. Chaturvedi (2006) found
28.5 kg P ha-1 as optimum for growth, plant height, tillers, grains spike-1,
1000 grain weight, grain and straw yields. Jiang et al. (2006) observed 108 kg
P ha-1 for higher leaf area index, tillers, ear bearing tillers and dry matter
accumulation. Khalid et al. (2004) applied 45 kg P ha-1 in wheat and obtained
maximum emergence, productive tillers, grain yield and biological yield.
Potassium is a one of special significance because of its active role in
bio-chemical functions of plant e.g. activating various enzymes, protein
formation, carbohydrates and fat concentration, tolerance to drought and
resistance to frost, lodging, pests and disease attack (Marschner, 1995). Thus
K deficiency in soil may results in yield losses (Ali et al. 2008). Increase in
cropping intensity and introduction of high yielding fertilizer responsive
cultivars have resulted in a considerable drain of soil K reserves. In the
present day, intensive and high yield oriented agriculture, there is a negative
K balance and soils are being mined for this essential element (Tan et al.
2005). Increased use of N without adding required K in soil has further
aggravated K deficiency (NFDC, 2003) because K play important role in
improvement of the growth indices. Increasing K amount in wheat grain increased
dry matter, 1000-grain weight, tillers, K contents in plant, The demand for plant nutrients is
expected to increase  continuously with
population growth (Kaarstad, 1997; Keeney, 1997), particularly in developing
countries. According to Keeney (1997), world population is expected to increase
by about 2.3 billion by 2020 and double by the year 2050. If meat and food
consumption in developed countries is matched by the rest of the world by the
mid-21st century, then grain and nutrient demand is expected to triple (Keeney,
1997; Kawashima et al., 1997). Keeping in mind that the amount of land used for
food production changed very slightly over the past few decades (Kaarstad,
1997; FAO, 1999), and may even have decreased in parts of the world due to
urbanization (Keeney, 1997), the nutrient load per unit area is steadily
increasing. All this implies that food production will have to be much more
intensive and efficient than ever before.