Agriculture Reference
In-Depth Information
in one of the signal transduction pathways or biosynthetic routes have been used to
find steps in HIPV emission crucial for indirect plant defense.
Knowledge of these interactions is increasing such that benign microbes and
carnivorous insects are now being deployed as bio-control agents. Future crop pro-
tection will function in a wholly integrated manner. Knowledge of the genetic quali-
ties of microbes will allow much greater specialised targeting of individual pests
and pathogens using bio-controls based on specific microbes, plant products and
biofriendly fertilisers which have properties supportive of crop growth and capable
of preventing pollution. Integrated crop management will be founded on detailed
computerised genetic profiles of the crop cultivar interacting with specific microbes
and populations of groups of microbe. Crop nutrition could be founded around the
properties of mycorrhizal organisms which are capable of extracting nutrient from
the soil and passing them to growing plants (Shtark et al.
2010
).
In particular this is likely to apply first to supplies of phosphorus. Warnings are
already sounding that rock phosphate supplies are being depleted. Balancing the
agricultural phosphorus (P) cycle is difficult, particularly for horticultural systems,
where crop products are exported off-site (Stockdale et al.
2006
). Sustaining soil
phosphorus concentrations usually relies on the input of some form of fertiliser.
These vary from those that are essentially unaltered to those that have undergone
a high degree of processing to increase phosphorus solubility and enrichment. One
of the major drawbacks associated with the direct use of rock phosphate is its poor
solubility in circum-neutral and calcareous soils, which currently requires long-
term and unnecessarily large application rates in order to satisfy crop demand.
Opportunities exist whereby the solubility and therefore bio-availability of sparing-
ly soluble rock phosphate can be enhanced without recourse to energy demanding
processes. A range of root traits have been shown to be beneficial in improving the
phosphorus-use efficiency of different crops and cultivars. These include: root prop-
erties (morphology and root hairs), uptake kinetics parameters and root-induced rhi-
zosphere changes (pH, organic acids and acid phosphatase). These responses have a
direct benefit for the crop itself, but may also have benefits for the crop rotation as
a whole; if phosphorus is mobilized from recalcitrant soil fractions and mobilized,
it is made available to following or adjacent crops. The mineralization of organic
matter by soil microorganisms provides an important supply of available phospho-
rus for plant growth. Hence phosphorus supply may be related to microbial activity
in soil. In addition, associations between plant roots and arbuscular mycorrhizal
fungi are able to use the available forms of phosphorus in the soil solution more
effectively than roots alone. A range of soil microorganisms including fungi and
bacteria have the ability to solubilize mineral forms of phosphorus in culture and
there is some evidence that this might also occur in soil (Dixon and Tilston
2010
).
Horticulture, as with agriculture has benefitted for more than a century from the
industrial discoveries which allowed the artificial fixation of atmospheric nitrogen
and the consequent production of nitrogenous fertilisers. The entire world food
supply now relies on the availability of these fertilisers since without them crop
yields would be only tiny fractions of current output. Unfortunately no such ben-
efit comes without penalties. In this case unrestricted use of particularly ammonia-
