Antonio Saraiva Muniz

Boron extraction and vertical mobility in Paraná State oxisol, Brazil

The deficiency or excess of micronutrients has been determined by analyses of soil and plant tissue. In Brazil, the lack of studies that would define and standardize extraction and determination methods, as well as lack of correlation and calibration studies, makes it difficult to establish limits of concentration classes for analysis interpretation and fertilizer recommendations for crops. A specific extractor for soil analysis is sometimes chosen due to the ease of use in the laboratory and not in view of its efficiency in determining a bioavailable nutrient. The objectives of this study were to: (a) evaluate B concentrations in the soil as related to the fertilizer rate, soil depth and extractor; (b) verify the nutrient movement in the soil profile; (c) evaluate efficiency of Hot Water, Mehlich-1 and Mehlich-3 as available B extractors, using sunflower as test plant. The experimental design consisted of complete randomized blocks with four replications and treatments of five B rates (0, 2, 4, 6, and 8 kg ha -1 ) applied to the soil surface and evaluated at six depths (0–0.05, 0.05–0.10, 0.10–0.15, 0.15–0.20, 0.20–0.30, and 0.30–0.40 m). Boron concentrations in the soil extracted by Hot Water, Mehlich-1 and Mehlich-3 extractors increased linearly in relation to B rates at all depths evaluated, indicating B mobility in the profile. The extractors had different B extraction capacities, but were all efficient to evaluate bioavailability of the nutrient to sunflower. Mehlich1 and Mehlich-3 can therefore be used to analyze B as well as Hot Water.

Ammonium sulphate on maize crops under no tillage

The objectives of this work were to evaluate the management of N and S (as ammonium sulphate) fertilization under no-tillage system on the components of maize productivity and on N and S accumulation in the crop, as well as to evaluate the minimum value of the Nitrogen Sufficiency Index (NSI 0.95) as an indicator for side dressing requirements. The experiment had a completely randomized block design with six treatments and four replications carried out in Red Latosol dystrophic soil (Hapludox), in Campo Mourao, Parana State, where the following treatments in summer growth maize were applied: T1- 120 kg ha-1 N in seeding; T2- 120 kg ha-1 N in side dressing; T3- 40 kg ha-1 N in seeding and 80 kg ha-1 N in side dressing; T4- 30 kg ha-1 N in seeding and 90 kg ha-1 N in side dressing, monitored by a chlorophyll meter using the Nitrogen Sufficiency Index (NSI); T5- 120 kg ha-1 N anticipated in wheat seeding; T6- without nitrogen fertilization. NSI was determined by the relationship between the leaf chlorophyll index (ICF) average of T4 plants and that one in the plot fertilized with 120 kg ha-1 N at the maize seed sowing (T1). During two years, ammonium sulphate was applied to the maize crop after wheat under no tillage system. In the first year, with adequate rainfall, the maize yield was similar to the one in which the complete ammonium sulphate dose application was done in maize seeding and side dressing. The anticipated fertilization to wheat seed sowing resulted in maize yield without difference from the parceled form. In the second year, with irregular rainfall, all treatments with N were similar and they increased maize yield compared to that without N fertilization. NSI of 0.95 was not efficient to evaluate maize N requirements in side dressing, and resulted in lower maize yield. N was accumulated mainly in the grains unlike S that accumulated in the plant shoots; both were highly correlated to maize productivity.

Monitoring and evaluation of need for nitrogen fertilizer topdressing for maize leaf chlorophyll readings and the relationship with grain yield

The study was carried out for two years in maize in succession to the wheat using no tillage system in a distroferric Red Latosol (Hapludox). Methods of management nitrogen fertilizer (120 kg ha-1) with ammonium sulphate were studied; the fertilizer was applied in maize sowing or in maize topdressing, and N with previous application in wheat sowing. In addition, leaf chlorophyll reading was used as an indicator for the need for topdressed nitrogen fertilizer. Nitrogen supply index (NSI) was shown to be effective at predicting need for topdressed nitrogen fertilizer for maize. The application of N improved the yield of the maize independent of the management system. The flowering stage was carried out at the appropriate time in order to estimate the nitrogen nutrition state and yield of maize using the relative chlorophyll level (RIC).