The Production of Trash and Its Effects as a Mulch on the Soil and on Sugarcane Nutrition*

Introduction For variety NCo.376, produced in six replications Trash conservation is practised primarily to obtain under standard dryland conditions, the amount of a reliable means of weed control in ratoon crops of oven-dry trash increased from 3.9 tons Per acre at sugarcane, and in Natal it is done with the knowledge 5 months of age to over 8 tons Per re at 20 months that a crop yield response may also be obtained, due of age. The amount of millable cane i ~ ~ ~ r e a s e d from largely to moisture conservation in an area where 10-6 tons at 5 months to 57.3 tons at 20 months. rainfall is severely limiting to crop production. Approximately a two-fold increase in the amount of However, in considering the conditions which might trash produced was thus accompanied by a five-fold be associated with a response to mulching compared increase in millable cane. with burning, it is essential to recognise that each A rapid increase of the millable caneloven-dry trash response might be the sum of several positive effects, ratio over the period from 5 months to 10 months and even the net result of both positive and negative of age was common to all varieties and treatments, effects. The production and composition of trash have but the absolute values of the ratios to vary therefore been studied, and long-term burning vs. significantly, and to maintain different levels during trashing have provided a means for the period of gradual increase after the crop was 10 measuring the effects of trash on the soil and crop months old. Varieties NzC0.376 and N:C0.382 were nutrition. fairly similar, as shown in Figure 1, but for variety