Direct field method for root biomass quantification in agroecosystems.

The present article describes a field auger sampling method for row-crop root measurements. In agroecosystems where crops are planted in a specific design (row crops), sampling procedures for root biomass quantification need to consider the spatial variability of the root system. This article explains in detail how to sample and calculate root biomass considering the sampling position in the field and the differential weight of the root biomass in the inter-row compared to the crop row when expressing data per area unit. This method is highly reproducible in the field and requires no expensive equipment and/or special skills. It proposes to use a narrow auger thus reducing field labor with less destructive sampling, and decreases laboratory time because samples are smaller. The small sample size also facilitates the washing and root separation with tweezers. This method is suitable for either winter- or summer crop roots. •Description of a direct field method for row-crop root measurements.•Description of data calculation for total root-biomass estimation per unit area.•The proposed method is simple, less labor- and less time consuming.

Effect of different cover crops on C and N cycling in sorghum NT systems.

In many no-till (NT) systems, residue input is low and fallow periods excessive, for which reasons soil degradation occurs. Cover crops could improve organic matter, biological activity, and soil structure. In order to study changes in soil carbon, nitrogen and microbial biomass a field experiment (2010-2012) was set up with sorghum (Sorghum bicolor Moench.) monoculture and with cover crops. Treatments were control (NT with bare fallow), rye (Secale cereale L.) (R), rye with nitrogen fertilization (R+N), vetch (Vicia villosa Roth.) (V), and rye-vetch mixture (VR) cover crops. A completely randomized block design with 4 replicates was used. Soil was sampled once a year at 0.06 and 0.12m depth for total C, microbial biomass carbon (MBC) and-nitrogen (MBN) determinations. Shoot and root biomass of sorghum and cover crops, litter biomass, and their respective carbon and nitrogen contents were determined. Soil temperatures at 0.06 and 0.12m depth, volumetric water contents and nitrate concentrations were determined at sowing, and harvest of each crop, and during sorghum's vegetative phase. NT led to a small increase in MBC and MBN, despite low litter and root biomass residue. Cover crops increased litter, root biomass, total C, MBC, and MBN. Relationships between MBC, MBN, and root-C and -N adjusted to logistic models (R(2)=0.61 and 0.43 for C and N respectively). Litter cover improved soil moisture to 45-50% water filled pore space and soil temperatures not exceeding 25°C during the warmest month. Microbial biomass stabilized at 20.1gCm(-2) and 1.9gNm(-2) in the upper 0.06m. Soil litter disappearance was a good indicator of mineral N availability. These findings support the view that cover crops, specifically legumes in NT systems can increase soil ecosystem services related to water and carbon storage, habitat for biodiversity, and nutrient availability.

Labranza reducida en el sector semiárido de la provincia de La Pampa

Sostiene los avances tecnológicos en el manejo de los suelos agrícolas muestran claramente que las tierras preparadas para la siembra de los cultivos por los métodos tradicionales que dejan la superficie pulverizada y sin cobertura de rastrojo, favorecen los procesos de erosión. Indica que el sistema de labranza reducida es un método para producir cultivos en el que se minimizan labores para la preparación de la sementera. La reducción de trabajos protege la estructura y mantiene los niveles de materia orgánica del suelo

Labranza reducida en el sector semiárido de la provincia de La Pampa

Sostiene los avances tecnológicos en el manejo de los suelos agrícolas muestran claramente que las tierras preparadas para la siembra de los cultivos por los métodos tradicionales que dejan la superficie pulverizada y sin cobertura de rastrojo, favorecen los procesos de erosión. Indica que el sistema de labranza reducida es un método para producir cultivos en el que se minimizan labores para la preparación de la sementera. La reducción de trabajos protege la estructura y mantiene los niveles de materia orgánica del suelo