| dc.description.abstract | The application of nitrogen through irrigation systems also
necessitates the application of other soluble nutrients
through this medium. Acid fertilizers are suitable for the
purpose, but are highly corrosive. Information on the
effects of these soluble products on the irrigation system
is not accessible. It is thus necessary to investigate the
influence of these chemicals on corrosion, to lay down
guidelines for these practices and to evaluate the
efficiency of the entire system.
It is known that in order to prevent accelerated corrosion
on galvanized irrigation equipment, pH-values of irrigation
water needs to be above six. To verify this, potensiometric
titrations were performed with an acid fertilizer in
irrigation waters of different qualities. Positive
correlations exist between dilution and the carbonate plus
bicarbonate content of irrigation water, which can be used
as a practical guideline. Electrical conductivity may be
used as an alternative. No other side-effects were noted.
The evaluation of acid fertilizers as source of phosphorus
and the practice of surface application of acid fertilizers
after planting, was carried out in pots with the aid of
radio-active phosphorus (32p). A high and low level of
phosphorus were applied. Four soil types with a phosphorus-status
(Bray 1) ranging from 2 to 49mgkg-l were used. Wheat
(Triticum aestivum L.) was planted and irrigation
conditions were simulated. Significant differences in yield
( dry material), as well as absortion of total-, soil- and
fertilizer applied phosphorus were noted between the
different soil types. The reaction of the control regarding
the yield, the absortion of total-, soil- and fertilizer
applied phosphorus is correlated to the phosphorus-status
of the soil. The high phosphorus application led to
significant increase in yield and absortion of total- and
fertilizer applied phosphorus.
No significant differences were noted between the two
fertilizer sources ( acid fertilizer and dry fertilizer),
with few exceptions. It was concluded that both are equal
sources of phosphorus.
The surface application of acid fertilizers led to
significant increases in absortion of total- and fertilizer
applied phosphorus. The yield was however, not
significantly increased. The concentration of phosphorus
applied on the surface led to increased availability and it
seems that plants prefer applied phosphorus.
The phosphorus applied through fertigation penetrated the
soil to a depth of about five centimetres. The highest
concentration of phosphorus still appear in the upper two
to three centimetres. No further movement took place during
the season. | en_US |
