Rice Y‐leaf nutrirnt analyses and midseason, foliar fertilization

Diagnosis and Recommendation Integrated System (DRIS) nutrient ratio norms and critical nutrient limits (CNL) have been used to successfully predict nutrient deficiencies in a number of crops; however, DRIS norms have not been available for rice (Oryza sativa L.). The purposes of these experiments were (1) to test the efficacy of the DRIS and the CNL methods for predicting nutrient deficiencies in rice and (2) to evaluate the potential of foliar fertilization for increasing rice yields. In 1984, DRIS norms were derived for rice Y‐leaves (the youngest mature leaf blade) taken at early internode elongation from a population of high yielding plots and treatments from various Arkansas rice experiments. These norms, and CNL were used in the three 1984 experiments. In 1985, separate sets of DRIS norms were prepared for the medium grain cultivar ‘Mars’ and for long grain cultivars of rice and used in four experiments. In these experiments, Y‐leaf samples were taken and nutrient ratios were determined. Foliar fertilizations, based upon DRIS‐predicted limiting nutrients, were made 5 to S days after sampling. In one experiment in 1984, yields were increased over the control by applying DRIS‐predicted limiting nutrients. In the other six experiments, treatments based on DRIS‐predicted limiting nutrients did not increase yields over the controls. In four of ten cases in which the CNL method predicted N deficiencies, N foliar fertilizations increased yield. However, an N response occurred in three cases in which N was not predicted to be deficient.