Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

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.

摘要 向日葵因对广泛气候条件的适应性以及可用于生物柴油生产，备受农户青睐。然而，针对碱性土壤中向日葵施肥的相关研究较为匮乏。本研究旨在评估碱性土壤栽培的普通向日葵（Helianthus annuus L.）的氮（N）、磷（P）施肥方案。本试验于巴西巴劳纳斯-RN（Baraúnas-RN）开展，供试土壤为钙质岩母质发育的典型雏形土（Haplic Cambisol），供试向日葵品种为H-251杂交种。试验处理为4个施氮水平（30、60、90、120 kg·ha⁻¹）与4个五氧化二磷（P₂O₅）施用量水平（30、60、90、120 kg·ha⁻¹）的完全组合。结果表明，向日葵的生长与产量随施氮量及五氧化二磷施用量的增加而显著提升。其中，施氮30 kg·ha⁻¹+五氧化二磷30 kg·ha⁻¹的处理最为经济，对应的籽粒产量达2378 kg·ha⁻¹。与该施肥方案对应的养分临界指标为：叶片氮含量28.2 g·kg⁻¹，叶片磷含量2.84 g·kg⁻¹，经梅利奇-1（Mehlich-1）浸提的土壤有效磷含量为6.75 mg·dm⁻³。