Factors affecting nitrogen utilization by sugarcane in South Africa.
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Date
1972
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Abstract
TIhe response of sugarcane to applied N in South Africa
varies considerably from one soil to another, particularly in
the plant crop. Responses to fertilizer N by ratoon cane are
generally much greater than those given by plant cane. Where
irrigation is practised yield response per unit of N is significantly
higher than that obtained under rain grown conditions.
Response of cane to N can be influenced by various
factors, some of which are able to bring about differences in
yield as great or greater than those obtained from the N fertilizer
itself. These include seasonal effects, time and method of N
application, the form of N applied, and the nature of the soil .
The N cycle in relation to sugarcane has been examined,
as several factors affecting response of cane to N are concerned
with the transformations which N undergoes in the soil - plant
system.
The potential of different soil series within the sugar
belt to mineralize N, greatly influences the response of plant cane
to applied N. The N supplying power of sugar belt soils is also
dependent upon how recently they were opened for cultivation,
and the length of time they remain dry prior to replanting.
However, accurate assessment of soil N available to cane remains
difficult, and it is probable that N recommendations will continue
to be made largely on an empirical basis of management and yield.
Incorporation of cane trash in the soil, and the C/N
ratio of cane roots may affect efficiency of N fertilizer usage
by the crop, particularly in the sandier soils of the industry
low in N, due to the immobilization of applied N. Apart from the soil pH effect as such, specific N
carriers are able to influence r ates of nitrification and thus
susceptibility to leaching, especially in the more weakly buffered
soils which constitute over 30% of the industry. It appears
likely that utilization of N by cane grown in these soils, could
be enhanced by the use of the nitrification inhibitor N-Serve.
Application of all the N to the furrow at time of planting
can cause severe leaching losses even in heavily textured soils.
Top-dressing some weeks after planting, results in more efficient
recovery of fertilizer N. Even so, only 25%-30% of N applied in
the widely used ammonium form is recovered by the above ground
parts of the cane crop.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1972.
Keywords
Sugarcane--South Africa., Theses--Soil science.