601-Current-Trends-in-Agronomy-SSR

131 Pages·2012·2.04 MB·English

Current Trends in Agronomy
(2012-13)

Department of Agronomy, College of Agriculture, CSK Himachal Pradesh
Krishi Vishvavidyalaya, Palampur-176062 (India)

Current Trends in Agronomy

SS Rana
Sr Scientist

Department of Agronomy, Forages and Grassland
Management, COA, CSK HPKV, Palampur-176062

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AGRON 601 3+0
Objective
To acquaint the students about recent advances in agricultural production
Theory
UNIT I
Agro-physiological basis of variation in yield, recent advances in soil plant-water
relationship
UNIT II
Globalization of agriculture and WTO, precision agriculture, contract farming, organic
farming, marketing and export potential of organic products, certification, labeling and
accreditation procedures
UNIT III
Crop residue management in multiple cropping systems; latest developments in plant
management, weed management, cropping systems, grassland management, agro-
forestry, allelopathy
UNIT IV
GIS, GPS and remote sensing for crop management, global warming, GM crops, seed
production technology; seed certification, seed multiplication, hybrid seed production,
etc.
UNIT V
Concepts of system approach in agriculture; holistic approach of farming systems,
dryland farming, sustainable agriculture and research methodology in Agronomy
Suggested Readings
Agarwal RL. 1995. Seed Technology. Oxford & IBH.
Dahiya BS & Rai KN. 1997. Seed Technology. Kalyani Publishers.
Govardhan V. 2000. Remote Sensing and Water Management in Command Areas:
Agroecological Prospectives. IBDC.
ICAR. 2006. Hand Book of Agriculture. ICAR, New Delhi.
Narasaiah ML. 2004. World Trade Organization and Agriculture. Sonali Publ.
Palaniappan SP & Annadurai K. 2006. Organic Farming - Theory and Practice.
Scientific Publishers.
Sen S & Ghosh N. 1999. Seed Science and Technology. Kalyani Publishers.
Tarafdar JC, Tripathi KP & Mahesh Kumar 2007. Organic Agriculture. Scientific
Publishers.

Contents
Topic Page
UNIT I
Agro-physiological basis of variation in yield 1
Recent advances in soil plant-water relationship 10
UNIT II
Globalization of agriculture and WTO 20
Precision agriculture 24
Contract farming 27
Organic farming, marketing and export potential of organic products, certification, 35
labeling and accreditation procedures
UNIT III
Crop residue management in multiple cropping systems; 49
Latest developments in plant management, weed management, cropping systems, 53
grassland management, agro-forestry, allelopathy
UNIT IV
GIS, GPS and remote sensing for crop management 71
Global warming 79
GM crops 82
Seed production technology; seed certification, seed multiplication, hybrid seed 85
production, etc.
UNIT V
Concepts of system approach in agriculture 98
Holistic approach of farming systems 104
Dryland farming 107
Sustainable agriculture 115
Research methodology in Agronomy 120

Distribution of marks
Hourly examination 10%
Mid-term 20-30%
Assignments 5%
End of term examination including practical 55-65%

CURRENT TRENDS IN AGRONOMY 2012-13

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Physiological aspects of photosynthesis and respiration have to be demonstrated in sorting out the
regulation and function of various components. If there are inefficiencies in these systems and if
causes can be identified, they would represent legitimate targets for genetic manipulation. Properties
of rubisco, alternative oxidase, and photorespiration process already loom as opportunities for genetic
manipulation. However, about their utilities we are yet uncertain. Serious reinvestigation of foliage
canopies offers promise for important gains in photosynthetic productivity of crops. First cycle of
such research, begun over 50 years ago, in which importance of strong advantages of erect leaves in
dense canopies and minimum interception by emergent reproductive structures was
demonstrated. Those properties are now credited with contributing to yield progress in maize (Fischer
and Evans, 1999).
Plant production is driven by photosynthesis. Key elements in the system are:
(i) the interception of photosynthetically active radiation (PAR, 400-700 nm spectral band),
(ii) use of that energy in the reduction of CO and other substrates (photosynthesis),
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(iii) incorporation of assimilates into new plant structures (biosynthesis and growth), and
(iv) maintenance of plant as living unit.
Achieving high yield is conceptually simple-
• maximize the extent and duration of radiation interception;
• use captured energy in efficient photosynthesis;
• partition new assimilates in ways that provide optimal proportions of leaf, stem, root, and
reproductive structures; and
• maintain those at minimum cost.
Crop yield comprises only a portion of biomass that accumulates over a crop cycle. Effective root and
canopy systems (including stem structure for foliage display), for example, generally must be
established before onset of reproductive phase. In addition, cost of maintenance increases as
vegetative biomass accumulates during season. Because crops are at mercy of spatial and
temporal variations in weather, plant spacing, supplies of water and nutrients, and in occurrence of
pests and disease. Therefore, flexibility in morphogenesis and acclimation of physiological systems is
a key requirement for achieving high and stable performance. Whether biological efficiency of these
processes has, or might be, improved through breeding are important questions.

Biomass and Other Morphological Traits
Just as impact of Green Revolution can be attributed mostly to improved partitioning of products of
photosynthesis to grain yield, progress in yield is strongly associated with improved harvest index
(HI). Morphological traits associated with increased yield potential include grain number and HI. Even
if HI could be raised to 60% from its current maximum value (50%), it implies that yields could only
be increased by a further 20% using HI as a selection criterion, unless total crop biomass is also raised.
Furthermore, improved partitioning by greater reduction in plant height is unlikely since research
suggests that optimal plant heights have already been achieved. Some studies have shown
increased biomass to be associated with yield increases.

Photosynthesis and Related Traits
By definition, improved yield cannot be attributed to better overall radiation use efficiency (RUE) in
cases where total biomass has not been improved. RUE in a crop context represents ratio of total
energy present in crop's biomass to that of solar energy incident on crop across its growth cycle. The
pre-anthesis vegetative growth rates were lower for most modern cultivars. Expression of higher
photosynthetic rate in absence of significant changes in biomass could be a pleiotropic effect of
improved partitioning to yield driven by high demand for assimilates during grain filling. Canopy
temperature depression is a direct function of evapotranspiration rate, which itself is
determined largely by stomatal conductance. These traits could also be pleiotropic effects of genetic

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CURRENT TRENDS IN AGRONOMY 2012-13

variability among lines for a number of physiological and metabolic processes including sink strength,
photosynthetic rate, vascular capacity, and hormonal signals.

Improvement in Nutrient Use Efficiency
Genetic gains in N use efficiency (NUE), defined as grain yield per unit of N available to plant (Ortiz-
Monasterio et al., 1997). While NUE almost doubled with introduction of height reduction (Rht) genes
in early 1960s, progress since Green Revolution has continued at a lower rate in parallel with more
modest improvements in partitioning to yield. Improvement in NUE has been associated with
improvements in both total N uptake and efficiency of utilization in terms of grain yield. The Green
Revolution varieties demonstrated genetic gains in yield even under severely N-limited conditions i.e.
2 to 2.5 t ha-1 yield levels. This trend has continued since 1966 with varieties of mid 1980s yielding
more than 3 t ha-1 under same conditions. Work in Argentina has demonstrated improvement in both N
and P use efficiency in modern varieties of wheat.

Adaptation to Density
Idea that higher yield potential could be achieved by designing a plant type that is well adapted to
commercial practice of sowing high density monocultures was introduced by Donald (1968).
Improvement in yield potential would appear to be more a function of improved adaptation to canopy
microenvironment, rather than macro-environmental factors such as climate. Selection for yield
potential in early generations can be enhanced by reducing interplant competition between genotypes
in bread wheat (Lungu et al., 1987), and durum wheat (Mitchell et al., 1982). The
conventional breeding approaches may lose yield potential by selecting against it.

Improving the Ideotype
Relatively few systematic studies, such as those described above, have been conducted to examine
physiological basis of yield improvement in post–Green Revolution era. Perhaps for this reason,
further investment is made in understanding which plant traits could be optimized to further improve
yield. Many traits have been suggested in literature as having potential to raise yield, but very few
have been examined in a systematic way for their potential to increase genetic gains when used as
selection criteria. They have not generally been introgressed into high-yielding backgrounds, and little
if any work has been conducted to assess potential complementarity between many morphological
and physiological traits which have potential to improve the crop ideotype.

Source and Sink
It is widely believed that yield gains are most likely to be achieved by simultaneously increasing both
source (photosynthetic rate) and sink (partitioning to grain) strengths. While most
experiments indicate that yield is primarily limited by growth factors prior to anthesis, source capacity
may have become more limited in modern cultivars. For example, experiments on a historic series of
spring wheats from Russia indicated that, while sink capacity has been improved in post–Green
Revolution period, improvement has also resulted in modern lines that are now more source limited
than those in previous eras. Using field-grown plots, spikelets from one side of the spike were
completely removed at flowering. Potential yield (i.e., in the absence of source limitation during grain
filling) was calculated from doubled grain weight of semidegrained spikes. Data showed that, while
potential yield per spike had been improved (i.e., the doubled grain weight of semidegrained spikes
was higher in more modern lines), extent to which potential was realized (i.e., potential vs. actual
spike yield) had declined in modern lines.
Reproductive stages of development, from initiation of floral development to anthesis, are pivotal in
determining yield potential, and especially rapid spike-growth phase which has a duration of 25 d in
irrigated spring wheat in northwest Mexico and Argentina. During this period, final grain number is
determined; a major factor determining subsequent partitioning of assimilates to yield, as well as
heavily influencing assimilation rate of photosynthetic apparatus during grain filling. Duration of
spike growth relative to other phenological stages shows genetic variation. This is associated with
sensitivities to photoperiod, vernalization, and developmental rate independent of these stimuli (i.e.,
earliness per se). Fischer (1975, 1985) established critical nature of the rapid spike-growth phase in

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