Abstract
Fertilizer use in no-till systems must be aligned with a correct interpretation of soil chemical attributes and crop demands. The objectives of this work were evaluate the effects of pre-sowing application of ammonium sulfate (AS) and of cover crops on the yields and soil chemical attributes of no-till cotton (Gossypium hirsutum L. r. latifolium Hutch) over two harvesting years. The experiment was arranged in randomized complete block design, with the plots in strips, and the variables were three cover crops (Raphanus sativus L., Avena strigosa L. and Avena sativa L.) and four AS doses (0, 150, 300, and 450 kg ha-1) applied over millet dry biomass. The cotton in the experimental plots was manually harvested on April 25, 2007 and April 24, 2008. The soil samples were collected between cotton rows in all plots on May 5, 2007 and May 12, 2008, at depths of 0.0-0.05, 0.05-0.10, and 0.10-0.20 m for soil fertility analyses. The increasing doses of AS induced lower soil pH, and calcium (Ca) and magnesium (Mg) levels in the superficial soil layer, as well as higher exchangeable aluminum (Al) and sulfur (S) levels until a depth of0.20 m. Seed cotton yields increased with increasing AS doses.
Highlights
Cotton is an important crop worldwide, with a high aggregated value due to its many processed derivates and the high consumer demand
The experiment followed a randomized complete block design arranged in strips, and the treatments consisted of three cover crops preceding the no-till cotton: forage turnip (Raphanus sativus L.), black oat (Avena strigosa L.) and white oat (Avena sativa L.), which were cultivated in strips under a no-till system during the winter, and four ammonium sulfate (AS) (200 and 240 g kg-1 N and S, respectively) doses (0, 150, 300, and 450 kg ha-1) applied over the dry millet biomass the day before the sowing of no-till cotton
In 2007 and 2008, increasing AS doses resulted in a pH decrease at a depth of 0.05-0.10 m, similar to the effects observed on the surface (0.0-0.05 m depth)
Summary
Cotton is an important crop worldwide, with a high aggregated value due to its many processed derivates and the high consumer demand. Fertilizer recommendations for cotton are based on soil and leaf analysis. It is necessary to interpret such results with respect to the field management history of the farm or region. Soil fertility evaluation aims to quantify the availability of soil nutrients in order to overcome deficiencies and promote the growth and development of. Agronomy plants (CANTARUTTI et al, 2007). Under ‘Cerrado’ conditions, there are no nitrogen (N) and sulfur (S) reference indices to assist with a safe recommendation
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