Abstract
The objective of this research was to evaluate the effect of combinations of nitrogen and sulfur rates in degraded signal grass (Brachiaria decumbens) pasture on their productive, morphological and nutritional attributes in the root system at four soil depths. The pasture used in the experiment was established over eight years ago in Entisol. Five nitrogen rates (0; 150; 300; 450 and 600 kg/ha/year) and five sulfur rates (0; 15; 30; 45 and 60 kg/ha/year) were combined in a fractionated factorial in a randomized block design, with three replications. Nitrogen was supplied as ammonium nitrate and sulfur as gypsum, and the rates were split into three times in the rainy season. The evaluations occurred at intervals of 35 days during the rainy season and 56 days in the dry season, in two consecutive years. Roots were collected with a 4-cm diameter auger at 0-10; 10-20; 20-30 and 30-40 cm soil depths. It was determined root dry matter, length and surface of the root system and nitrogen and sulfur concentrations in roots. Nitrogen rates applied in two consecutive years in the pasture affected dry mass, length, surface and nitrogen concentration in signal grass root system. Rates of sulfur by themselves or combined with nitrogen rates do not affect attributes of root system.
Highlights
Millions of hectares of Brazilian pastures are degraded or under degradation
In the experiments in which roots were usually evaluated, only the roots dry mass is measured, because it is more obtained than other attributes of the root system, such as length, surface, diameter and distribution in soil depth (Voorhees et al, 1980)
According to Anghinoni & Meurer (1999), the root system of grasses is concentrated in the surface soil depth, mainly in the 0-5 cm layer
Summary
Brachiaria decumbens (signal grass) is the main species under degradation and Scurlock & Hall (1998), less than 10% of the experiments with pastures evaluated the grass root system. In the experiments in which roots were usually evaluated, only the roots dry mass is measured, because it is more obtained than other attributes of the root system, such as length, surface, diameter and distribution in soil depth (Voorhees et al, 1980). Most of the root mass of grasses (approximately 80%) is concentrated in the upper 15 cm soil depth (Barker et al, 1988; Brazil et al, 2000). According to Anghinoni & Meurer (1999), the root system of grasses is concentrated in the surface soil depth, mainly in the 0-5 cm layer
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