Diagnosis of the Nutritional Status of Rapeseed Crop (Brassica napus) Based on Nitrogen and Sulfur Dilution Curves

Abstract

For obtaining high yields in the rapeseed crop it is necessary to complement nitrogen (N) with adequate sulfur (S) nutrition. The aim of this study was to determine the diagnostic indicators of nutritional status of the crop in reference to nitrogen and sulfur for optimal plant grain and oil production. Equations were obtained for sulfur and nitrogen critical dilution (Nc = 5.21 MS-0, 36 and Sc = 1.22 e-0, 18MS, respectively). From the equations, the sulfur nutrition critical index was 0.88, and 0.74 for maximum biomass production in elongation and grain respectively. For nitrogen only a critical value of 1.04 was found, whereas, for the production of grain we observed that under the condition of sufficient sulfur nitrogen limitation did not exist over the entire range of nutritional status studied. Instead, under the condition of limiting sulfur yield response to nitrogen nutritional status was linear. The results indicate the need for a minimum amount of S absorbed to reach maximum yield range. The dilution rate for critical sulfur was lower than nitrogen dilution rate, for which the Nt:St was not useful in predicting the nutritional status of crop growth and grain yield, but it did help predicting the oil concentration with a critical value of 7.7.