Aggregate stability by the "high energy moisture characteristic" method in an oxisol under differentiated management

Abstract

SUMMARYStudies testing the High Energy Moisture Characteristic (HEMC) technique in tropical soils are still incipient. By this method, the effects of different management systems can be evaluated. This study investigated the aggregation state of an Oxisol under coffee with Brachiaria between crop rows and surfaceapplied gypsum rates using HEMC. Soil in an experimental area in the Upper São Francisco region, Minas Gerais, was studied at depths of 0.05 and 0.20 m in coffee rows. The treatments consisted of 0, 7, and 28 Mg ha -1 of agricultural gypsum rates distributed on the soil surface of the coffee rows, between which Brachiaria was grown and periodically cut, and compared with a treatment without Brachiaria between coffee rows and no gypsum application. To determine the aggregation state using the HEMC method, soil aggregates were placed in a Büchner funnel (500 mL) and wetted using a peristaltic pump with a volumetric syringe. The wetting was applied increasingly at two pre-set speeds: slow (2 mm h -1 ) and fast (100 mm h -1 ). Once saturated, the aggregates were exposed to a gradually increasing tension by the displacement of a water column (varying from 0 to 30 cm) to obtain the moisture retention curve [M = f (Ψ Ψ Ψ Ψ Ψ)], underlying the calculation of the stability parameters: modal suction, volume of drainable pores (VDP), stability index (slow and fast), VDP ratio, and stability ratio. The HEMC method conferred sensitivity in quantifying the aggregate stability parameters, and independent of whether gypsum was used, the soil managed with Brachiaria between the coffee rows,

Aggregates morphometry of a Inceptisol under conservationist system

“…As noted by Silva et al (2013Silva et al ( , 2014 in areas of dystrophic Red Latosol (Oxisol) under the same management system, both gypsum as organic matter are directly related to soil aggregation, since they change the chemical balance. Thus, at the same locations where samples were removed for aggregate study (planting line and interline as well as under native vegetation), three samples were collected deformed samples at 0.00 to 0.20m (Hz A) and 0.40 to 0 80 m (Hz Bi) depths for organic matter and exchangeable calcium measurements.…”

“…Two Mg ha-1 of dolomitic limestone (16-17% MgO) and 220 g m -1 of 08-44-00 mineral fertilizer with 1.5% Zn and 0.5% B were applied into the planting furrows, aiming at fertilizing from 0.0 to 0.60 m of soil depth. Three months after planting, a further gypsum dose of 7.0 kg m -1 (28 Mg ha -1 ) was used, as recommended by consultants and farmers for such management system, as described in Serafim et al (2011); it was spread over soil surface (without incorporation) and along cultivation line (SILVA et al, 2014).…”

“…In the first year after planting, it was applied 100 kg ha -1 of ammonium nitrate over total area. Yet in the second, aiming at improving cut material yield and organic matter increment, the soil covered with the grass (interlines) received 600 kg ha -1 K 2 O into four fractional applications throughout the year (SILVA et al, 2014).…”

“…The positive results in terms of aggregation in the crop line have probably conditioned improvements in soil-air-water relationship, favoring root growth at deeper depths, and therefore greater soil exploration for water and nutrients (CARDUCCI et al, 2014a(CARDUCCI et al, , 2014bSERAFIM et al, 2011;SILVA et al, 2013SILVA et al, , 2014.…”

High rates of agricultural gypsum affect the arbuscular mycorrhiza fungal community and coffee yield

“…As a result of agribusiness development in the Cerrado and improved techniques for neutralization of subsoil acidity, gypsum application has become a common practice to increase coffee bean yield (Serafim et al 2011). It is known that the application of agricultural gypsum brings several benefits, namely, increased concentration of Ca 2+ in the soil solution (Ramos et al 2013), more even distribution of roots (Carducci et al 2015) and, consequently, reduced water deficit of the crops (Silva et al 2014).…”