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Agronomic performance of acid-based liquid fertilisers on winter wheat.
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1999-12-01
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Burke, J.I., O'Reilly, B., Gallagher, E.G., Agronomic performance of acid-based liquid fertilisers on winter wheat, End of Project Reports, Teagasc, 1999.
Abstract
In the early 90’s, a new and novel means (liquid Flex system) of crop fertilisation
was launched on the Irish market which was capable of supplying the crop’s total
nitrogen, phosphorus, potassium and trace element requirement in liquid form,
formulated to meet specific crop requirements. This system included novel
chemistry, untested under Irish conditions and with little specific reference in the
scientific literature.
The chemistry of the liquid Flex system consists of an acid-based material. Stable
compounds i.e. urea sulphate, urea phosphate and urea-metal complexes are
formed by the reaction of urea with sulphuric acid, phosphoric acid and metal
salts, respectively. Interest in these materials has been generated because they
possess a number of physical and chemical characteristics, which, in theory,
should be beneficial. However, the ability of the Flex system to effectively supply
nutrients to the plant has not been researched.
A field and greenhouse experimental programme was carried out over the three
seasons, 1996-1998 to compare acid-base/urea-metal complexes with conventional
fertilisers and to investigate whether this unconventional chemistry could lead to
increased biological efficiency. The trial programme evaluated the Flex system,
both as individual components and as a complete fertiliser.
In field comparisons, formulation of P as urea phosphate gave similar results to
conventional granular superphosphate in terms of grain yield, recovery of P by the
crop and grain quality, regardless of soil type. This was supported by the results
from the greenhouse experiment.
In field comparisons of the main soil-applied liquid Flex source of N, i.e. N24
(urea with the addition of a standard level of acid and metal salts) with
conventional N formulations, N24 gave poorer performance than CAN and
granular urea in warm dry conditions due to insufficient inhibition to substantially
reduce ammonia volatilisation. In wet conditions, the slow release of N from
inhibited urea may have reduced the potential loss from leaching or denitrification,
and led to a better performance than CAN or urea. The additional product of the Flex system, i.e. liquid Flex urea - N18 (urea with
the addition of metal salts), applied as a foliar spray, was no more efficient than
liquid urea as a late N source. The Flex urea had the disadvantage that it gave
higher scorch levels than conventional liquid urea. When flag leaf scorch was
excessive, grain yield was affected and quality suffered, with reduced grain and
hectolitre weights.
Where early application of P may have been critical to obtain maximum response,
the N that accompanied the early application of P as urea phosphate was most
likely lost through leaching. The application of large quantities of K in any one
application with the liquid system was restricted due to solubility problems, which
ultimately resulted in delayed application in soils with low K levels.
The Flex system does not lead to increased biological efficiency. However, as
farms get bigger and greater emphasis is placed on the reduction of water and air
pollution, the liquid Flex system may become attractive because of its practical
advantages in handling, storage and application and the ability to tailor-make
specific formulations for given crop requirements.