Technical Series Number 17, July 1995
The soils of the flat part of the Cauca River Valley exhibit a certain degree of heterogeneity in their physical, chemical, and biological properties. A semi-detailed soil study conducted by the Agustín Codazzi Geographic Institute (IGAC, 1980) established ten representative soil groups for the area. Extrapolation of the results obtained from a given soil to others with similar characteristics belonging to the same group has made research on sugarcane nutrition more efficient (Quintero, 1992).
Some results obtained from research on nitrogen (N) and potassium (K) fertilization under the soil and climate conditions of the Cauca River Valley demonstrate that the recommendations for these nutrients depend not only on soil characteristics but also on the sugarcane variety and the cutting number (Quintero, 1993). The differences found in the estimated recoverable sugar concentration (ERC) between the MZC 74-275 and PR 61-632 varieties as a result of potassium applications to the soil are very important; the PR 61-632 variety significantly increased the ERC when potassium was applied to soils with relatively high exchangeable potassium contents, a characteristic that made its response unlikely. On the other hand, with the
variety MZC 74-275, some responses in sugar concentration have been detected only in soils with low exchangeable potassium contents (CENICAÑA, 1989; CENICAÑA, 1990).
In general, CENICAÑA's fertilizer research is conducted with commercial varieties. However, imported varieties or those developed by our Research Center that possess outstanding characteristics that warrant consideration are continually emerging. These varieties are delivered to sugar mills and growers for commercial propagation without adequate management guidance, especially regarding water and fertilizer requirements.
From these considerations, it is easy to deduce the inconvenience of generalizing fertilizer doses for the different sugarcane varieties currently planted in the different soils of the Cauca River Valley. This problem could potentially be resolved with management trials, through which the most appropriate doses of the nutrients that most limit the production of commercial and promising varieties under our ecological conditions could be determined.
Nitrogen management tests are carried out on semi-commercial-sized plots and correspond to simple experiments through which it is possible to determine nitrogen recommendations for the most important varieties, in such a way that these recommendations are adjusted to the real needs of the soils and the prevailing conditions of the sites where they are carried out.
