| Agricultural Uses | The dry residue of fine-stemmed cereal crops after the
grain is removed is called straw. It is a fibrous
cellulosic component (1 to 1.5 m long), similar to that
found in hardwood. It can be pulped by the alkaline
process to yield speciality papers.
Straw is a major component of farmyard manure
0I.t has N, P and K in small quantities. Dry straw
is almost fully organic, carbonaceous (with a carbon to
nitrogen ratio of 40-80:1) and contains only small
amounts of nutrients (0.4 to 0.5 % nitrogen, 0.25 to 0.4%
phosphorus and 0.35 to 0.45% potassium). If straw is plowed back into the soil, it decomposes to release
nutrients and occasionally, undesirable organic acids and
ethylene gas. Incorporating straw into wet soil is not
advisable since it creates waterlogging and retains
herbicide residues.
If straw is burnt, its organic matter and N are lost but
K and P return to the soil. Straw may serve as clean, dry,
bedding material, providing comfort to animals and
conserving their excreta.
Straw when incorporated directly into the soil
decomposes slowly. In fertile aerobic soils with sufficient
(but not excess) water, however, straw can make
considerable contribution to the soil organic matter,
especially in areas of intensive cereal production. The
other favorable conditions for effective decomposition of
carbon in straw are the availability of nitrogen in the soil
or plant and a pH regulated by lime. In this way, it helps
to increase the water holding and nutrient retention
capacities of the soil, improve soil structure and reduce
insidious erosion which happens when the soil organic
matter level falls below the critical point.
The management of straw incorporation is not simple
and warrants that the following rules be followed. (i)
Because of the bulky nature of straw, addition must be
chopped into short lengths for easier incorporation and
increased speed of decomposition. (ii) Because of high
carbon to nitrogen ratio of straw, additional fertilizer
nitrogen becomes necessary. (iii) Great care must be
taken to get a good spread of straw through the topsoil.
When wrongly incorporated, it will decompose
anaerobically, giving an obnoxious odor, and prove toxic
to roots.
Straw fiber has many commercial uses in industries
dealing with paper, fuel, chemicals, single cell protein,
boards and crafts. |