Application of the diagnosis and recommendation integrated system (DRIS) for different soils and time of foliar sampling on sugar-cane (Saccharum spp.) ratoon crops

Abstract

In order to study the Diagnosis and RecomendationIntegrated System (DRIS), this technique was compared with that of foliar diagnosis based on threshold values. The effect of different foliar sampling times of ratoon crops grown in the 4 great soil groups was observed. The trials were based on the N x P x K x L factorial design, where L * surface and sub-surface placement of fertilizers. Application rates were: 0 - 60 - 120 - 180 kg N/ ha; 0-45 kg P(2)0(5)/ha; and, 0 - 90 - 180 kg K(2)0/ha. The soils under study were: Latosolic B "Terra Roxa" (LR); Red-Yellow Podzolic - Laras variation (PVls); Red-Yellow Latosol sandy phase (LVa), and Ortho Dark Red Latosol (LE). In the latter soil (LE), the cane was grown with and without irrigation. Variety CB 41-76 was used, and lieaf +3 was collected at 3, 4, 5 and 6 months of age of the ratoon crop. The plots comprised 7 rows 10 m long, where only the 3 central rows were harvested and the other considered as borders. The inter-row spacing was 1.5 m. The data obtained showed that the sub-surface placement of fertilizers did not bring about any positive effect on cane or sugar yield, with the exception of plants grown in PVls soil. In general, sugar-cane yields were increased, in linear form, with the application on nitrogen and potassium, with the exception of potassium in LR soil. Phosphorus increased cane yield for LE, LR and PVls soils, and brought about an increase in sugar production per area for LE an LR soils. Irrigation did not benefit ratoon crops planted in LE soils. Determination of critical levels in foliar diagnosis for N and K was only possible for some of the times of +3 leaf sampling, whereas for phosphorus it was was feasible for any of the times of foliar sampling. Time of plant tissue sampling and soil type affected the critical levels of N and K. On the other hand, the DRIS approach proved to be an adequate methodology for N, P and K diagnosis in sugar cane ratoon crops, and the interpretation of the transformed indices does not substantially change with foliar sampling time. Also, application of the DRIS on different types of soil is feasible.