Sugarcane irrigation regime results, on red Ferrallitic soils.

Gonzalez F. R. Sugarcane irrigation regime results, on red Ferrallitic soils.

Doctor in Agriculture Science thesis, 1986, Cuba.

Two experiments on sugarcane irrigation, with eight harvests, one of which was under conditions of compensation lysimeter Mariotte type, and the other with experimental plots, were carried out in under to clarify and define the following objectives: to determine maximum and real evapotranspiration under different irrigation regimes, to evaluate influence of different irrigation regimes on sugarcane growth, to evaluate the response of sugarcane to irrigation.

The research was carried out on red Ferrallitic soil at Antonio Mesa Sugarcane Experiment Station, in Jovellanos, located in the centre of Matanzas province. The cane yields was obtained in the lysimeter with three replicates, during the research years the yield varied from 79 to 120 t/ha. Maximum evapotranspiration was around 2 000 mm in January plant cane, harvested with 14, 5 months; 1 700 mm in April ratoon and 1 450 mm in January ratoon, both harvested with twelve months age.

A high correlation between accumulated maximum evapotranspiration values and a class A evaporation tank was found. A logistic regression equation offered best adjustment. The bioclimatic (Et/Eo) coefficients varied according to crop number and date of initiation of the vegetative cycle. A high relation between plant height and accumulated evapotranspiration was found. The logistic equation presented the best adjustment between these two variables.

The use of irrigation in red Ferrallitic soils allowed increasing sugarcane stalk and sugar yields per unit area. The period from planting to canopy closures, that coincides with the rainy season under January planting conditions, is the most important stage for sugarcane irrigation Soil moisture in the dry period should not descend below 80% field capacity, in the 0- 30 cm soil layer.

On account of the high correlation found between soil moisture content in the 0- 30 cm layer vs. 0- 50 cm 0- 80 cm and 0- 100 cm, for practical purposes, in this type, sampling at 0- 30 cm depth can be used to estimate, with the selected linear regression equation, the percentage of capacity at the desired depth, and with this result, calculate the required net irrigation dosage.

It is necessary additional experiments to continue studying the direct and no direct effect of irrigation on sugarcane sucrose content. The projected total net irrigation dosage, in m 3 /ha, for different sugarcane crop types, organized in decreasing order for the 75 % probability is as follow: 4450, 4050 and 3950 cubic meter for January plant cane, January ratoon and April ratoon respectively. The additional net profit by the irrigation effect, considering a 25 cents per pound sugar price, varied from 107, 57 to 245, 76 pesos/hectare.

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