Effects of Concentration of Sodium Hexametaphosphate and Dispersion Period on the Dispersability of Three Alfisols at Samaru, Northern Nigeria.

Strongly aggregated Soils are not readily dispersed with the standard 5% Calgon (sodium hexametaphoshate (SHMP) solution, under the 5- minute shaking or 1- minute stirring (dispersion) periods. The feasibility of better dispersion at higher SHMP concentrations and/ or longer dispersion periods was, therefore, explored on three Alfisols with differing drainage classes, namely, a well drained Oxic Haplustalf, a moderately well drained Typic Plinthastalf ,and a poorly drained Aquatic Haplustaff. To concurrently determine both the most effective SHMP concentration and a dispersion periods, graded concentrations of SHMP, viz: 5%, 7.5%, 10%, and 12.5%, and five dispersion periods of 5 minutes, 30 minutes, 1 hour, 2 hours and 3 hours were applied. The results showed that the 5- minute dispersion period remains ideal for the three Alfisols. However, the effect of SHMP concentration varied; the well drained Oxic Haplustaff required double the standard concentration from 5% to 10%, the moderately well drained Typic Plinthustalf, a 50% increase to 7.5%, while the poorly drained Aquatic Haplustaff, just the standard (5%) SHMP concentration for effective dispersion.Nigerian Journal of Soil Science Vol. 17 2007: pp. 1-

Do soil carbon sequestration and soil fertility increase by including a gramineous cover crop in continuous soybean?

Cover cropping is a farming practice that may improve C sequestration and soil fertility, but these effects can vary under different edaphoclimatic conditions. The effects of including a winter gramineous cover crop (CC) in continuous soybeans were evaluated in three long-term experiments (8 yr) on one coarse-textured soil and two finetextured soils in the Pampas region of Argentina. The impacts of CC on soil C sequestration, soil nutrient availability, soil organic C (SOC), and N contents of soil particle size fractions were also determined. The inclusion of CC only increased SOC stock by 3.1 Mg ha-1 in the coarse-textured soil (CTS). The labile C fraction in the 0–5-cm depth increased in both the CTS and the fine-textured soils (FTS) by 263% and 93%, respectively. Soil N also increased in the labile fraction by 119% and 112% when a CC was used in the CTS and FTS soils, respectively. Moreover, the inclusion of a CC decreased soil P availability in one experiment (4.9 kg ha-1) and increased soil manganese in two experiments (11 kg ha-1 on average). The inclusion of a gramineous CC in a soybean monoculture increased the C balance, particularly in coarse-textured soils. Considering that soil N was similarly affected, the C/N ratio was not impacted.Fil: Beltran, Marcelo Javier. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Suelos; ArgentinaFil: Galantini, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Salvagiotti, Fernando. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Oliveros; ArgentinaFil: Tognetti, Pedro M. Universidad de Buenos Aires. Facultad de Agronomía. IFEVA; Argentina.Fil: Bacigaluppo, Silvina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Oliveros; ArgentinaFil: Sainz Rozas, Hernan Rene. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Barroco, Mirian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria General Villegas; Argentina.Fil: Barbieri, Pablo Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Unidad Integrada. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin