Water and solute transports in the vadose zone depend on the distribution, size, shape and configuration of the pores. They affect the soil hydraulic properties and, consequently, the directly related processes such as water storage, infiltration, groundwater recharge, and also erosion and runoff. Soils amended with biochar are prompt to improve their physical and hydraulic properties. Biochar addition alters not only porosity, the water retention pattern and the derived pore distribution, but also the hydraulic conductivity under saturated and unsaturated conditions. In our work, two different doses (2.5 and 5% dry wt.) were added to two textured soils (sand and sandy loam). The unsaturated hydraulic conductivity and saturated hydraulic conductivity were measured under laboratory conditions. The obtained results show the positive effect of biochar on the hydraulic functions. For the sandy soil, the higher the dose of biochar, the more constant and relatively higher is the hydraulic conductivity up to - 40 kPa. At less negative matric potentials (< -10 kPa), the unamended sandy loam soil showed a slightly higher unsaturated hydraulic conductivity, compared to the amended soils. These results underline that biochar addition enhances the transport of water under unsaturated conditions by reducing the formation of larger pores while also intensifying the finer inter-particle pore formation.
Para el año 2050, se prevé que la población será un tercio mayor a la actual. Esto se convierte en un reto para la agricultura por aumentar su producción generando el menor impacto posible al ambiente. La labranza del suelo ha permitido aumentar áreas de siembra en detrimento de su capa arable, contribuyendo a degradar en forma progresiva la superficie del suelo y facilitando la erosión. La erosión por labranza se ve influida directamente por la compactación provocada por el paso de la maquinaria. Sistemas de tráfico agrícola controlado, agricultura de precisión y rodajes alternativos han sido utilizados para minimizar los efectos de los pases de los equipos sobre el campo. En Costa Rica, la adopción de nuevas tecnologías, la selección adecuada de equipos, el respeto a la legislación vigente e investigación sobre el impacto de la labranza en la degradación del suelo, constituyen un reto para las autoridades, los productores y la academia.
Biochar is a carbon-rich organic material, obtained by the thermochemical conversion of biomass in an oxygen-limited environment, used as a soil amendment to stimulate soil fertility and improve soil quality. There is a clear need in developing countries for access to low cost, low technology options for biochar production, for example, top-lit updraft (TLUD) stoves, which are popular and spread worldwide. However, TLUD biochars are inevitably very variable in their properties for a variety of reasons. We present laboratory triplicate tests carried out on TLUD biochars obtained from waste pinewood and a Guadua bamboo. Analyzed properties include specific surface area (A-BET), porosity, skeletal density, hydrophobicity, proximal and elemental composition, cation exchange capacity (CEC), relative liming capacity and pH. SEM images of the bamboo and wood biochars are compared. The biochars were mixed with composted human excreta at 5% and 10% biochar content, and available water content (AWC) was analyzed. Operating temperatures in the TLUD were recorded, showing different behaviors among the feedstocks during the process. Differences in operating temperatures during charring of the bamboo samples seem to have led to differences in A-BET, hydrophobicity and CEC, following unprecedented trends. For the mixtures of the biochars with compost, at 5% biochar no significant differences were observed for AWC. However, in the 10% biochar mixtures, bamboo biochar showed an unexpectedly high AWC. Overall, variations of chemical and physical properties between bamboo biochars were greater, while pinewood biochars showed similar properties, consistent with more homogeneous charring temperatures.
Soil degradation and water stress in Costa Rica challenge the production of highly sensitive crops. This work is aimed at evaluating the physical and chemical changes in sandy loam (SL) and a silt loam (SiL) soil when amended with bamboo biochar while estimating the enhancement of tomato productivity. Biochar, obtained from Guadua Angustifolia bamboo feedstock, was mixed into sieved bulk soil substrate from the topsoil, from Andosol and Umbrisol groups, at application rates of 1, 2.5, and 5% (dry mass). Physicochemical and morphological properties of biochar such as pH, hydrophobicity, scanning electron microscopy images, helium picnometry, specific surface area by the Brunauer–Emmett–Teller (BET) method, CHNS, and ash content were determined. Soil hydrophobicity, acidity, electrical conductivity, cation exchange capacity and water retention, available water content, and air capacity were analyzed for the amended soils. Tomato yield was quantified after a harvest period of two months. The admixture of biochar did not significantly increase soil cation exchange capacity but increased water retention in the range of available water content. Class A (>200 g) tomato yield increased 350% in the SL and 151% in the SiL. Class B (100–200 g) tomato yields increased 27% in the SL but decreased about 30% in the SiL. Tomato yield response seems attributable to variation of water retention capacity, available water content, and air capacity. These results support the use of adapted water management strategies for tomato production based on soil physical changes of biochar.
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