Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

Daniely F Braga,Everaldo Zonta,Adelson P Araújo,Hemmannuella C Santos,Fabio H T De Oliveira

doi:10.1590/1807-1929/agriambi.v22n2p101-106

Abstract

ABSTRACT Sunflower is a crop that has aroused the interest of farmers because of its adaptability to wide climatic conditions and for its use in biodiesel production. However, there are only a few studies on sunflower fertilization in alkaline soils. This study aimed to evaluate nitrogen (N) and phosphorus (P) fertilization in sunflower (Helianthus annuus L.) cultivated in alkaline soil. A field experiment was carried out in Baraúnas-RN, Brazil, in a Haplic Cambisol derived from calcareous rock, where the sunflower H-251 hybrid was cultivated. The treatments were a combination of four doses of N (30, 60, 90 and 120 kg ha-1) and four doses of P2O5 (30, 60, 90 and 120 kg ha-1). Sunflower growth and yield increased with the doses of N and P2O5. Doses of 30 kg ha-1 of N and 30 kg ha-1 of P2O5 were more economical, corresponding to grain yield of 2378 kg ha-1. Critical levels associated with these doses of N and P2O5 were 28.2 g kg-1 for N leaf content, 2.84 for P leaf content, and 6.75 mg dm-3 for soil available P extracted by Mehlich-1.

Highlights

Sunflower (Helianthus annuus L.) has high potential for cultivation in Northeast Brazil because of its easy adaptation, great agro-energetic potential, easy management and good economic performance
Considering the increasing importance of sunflower in the Brazilian semi-arid region and the lack of research on its fertilization in alkaline soils of the northeast region, this study aimed to evaluate the response of sunflower to nitrogen and phosphate fertilizations in alkaline soil at the Apodi Plateau, RN, Brazil
Plant height was higher with the increment in N and P2O5 doses up to the maximum value of 1.86 m, corresponding to the doses of 99 kg ha-1 of N + 99 kg ha-1 of P2O5 (Y = 1.40 + 0.00325**N – 0.00001646*N2 + 0.006023**P – 0.00003035**P2, R2 = 0.89 - Figure 1)

Summary

Introduction

Sunflower (Helianthus annuus L.) has high potential for cultivation in Northeast Brazil because of its easy adaptation, great agro-energetic potential, easy management and good economic performance. In the 2014/2015 season, sunflower production (grains) in Brazil reached 153 thousand tons, with mean yield of 1,374 kg ha-1 (CONAB, 2016). In the Northeast region of Brazil, sunflower is still not much cultivated and, when cultivated, low yields are obtained because of the low technological level used by farmers. Alkaline Cambisols in Brazil, in general, exhibit very low contents of available phosphorus, micronutrients and organic matter, requiring fertilizations for adequate crop development (Lemos et al, 1997). N is a crucial element for seed and oil production (Alves et al, 2016), and P is directly related to seed production and quality (Silva et al, 2011)

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Results