Coffee is one of the most commonly traded agricultural commodities globally. It is important for the livelihoods of over 25 million families worldwide, but it is also a crop sensitive to climate change, which has forced producers to implement management practices with effects on carbon balance and water use efficiency (WUE) that are not well understood due to data scarcity. From this perspective, we propose crop canopy coupling to the atmosphere (Ώ) as an index of resilience and stability. We undertook an integrated observational approach for the scaling-up of measurements along the soil–plant–atmosphere continuum at different stages of the coffee crop phenological cycle. Additionally, we develop this perspective under pronounced climatic seasonality and variability, in order to assess carbon balance, WUE, and agroecosystem resilience in a sun-grown coffee field. Further, we devised a field layout that facilitates the measurement of intrinsic, instantaneous, and actual water use efficiency and the assessment of whether coffee fields differ in canopy structure, complexity, and agronomic management and whether they are carbon sources or sinks. Partitioning soil and canopy energy balances and fluxes in a sun-grown coffee field using eco-physiological techniques at the leaf and whole plant levels (i.e., sap flow and gas exchange), as proposed here, will allow the scaling-up to whole fields in the future. Eddy covariance was used to assess real-time surface fluxes of carbon, gross primary productivity (GPP), and evapotranspiration, as well as components of the energy balance and WUE. The preliminary results support the approach used here and suggested that coffee fields are CO₂ sinks throughout the year, especially during fruit development, and that the influence of seasonality drives the surface–atmosphere coupling, which is dominant prior to and during the first half of the rainy season. The estimated WUE showed consistency with independent studies in coffee crops and a marked seasonality driven by the features of the rainy season. A plan for the arborization of the coffee agroecosystem is suggested and the implications for WUE are described. Future comparison of sun- and shade-grown coffee fields and incorporation of other variables (i.e., crop coefficient-KC for different leaf area index (LAI) values) will allow us to better understand the factors controlling WUE in coffee agroecosystems.

Introduction. Simulation models are a tool to study crop behavior under different climatic and water conditions and agronomic management practices. Objective. To evaluate the AquaCrop model for estimating yield and water productivity in soybean var. CIGRAS-06. Materials and methods. The study was carried out at the Estación Experimental Agrícola Fabio Baudrit Moreno of the University of Costa Rica, in Alajuela, Costa Rica, from June 6 to October 23, 2018. The AquaCrop v. 7.1 model was used to simulate soybean crop development and yield. Simulated data on canopy cover, biomass production, and yield were compared with experimental data from a plot planted with soybean variety CIGRAS-06. Soil parameters measured in the field and generated with pedotransfer equations were used. Results. Predictions of yield, total biomass, and canopy cover were good (similarity values: d ≥ 0.97), but predictions of leaf coverage during the early crop cycle were susceptible to improvement. Differences between the two types of soil parameters used did not significantly affect the final simulation. Conclusions. AquaCrop successfully simulated soybean yield, biomass, and leaf coverage. Water productivity simulation was higher than values reported in the literature.

Knowledge of the soil carbon stock (SCS) is vital for appropriate farming practices management, ie. tillage and to monitor SCS changes as mitigation strategies of carbon footprint. This study aims to quantify the variability and spatial distribution of the SCS. In an area of 1 ha 45 micro-pit (1 x 0.8 x 1 m) were divided into four strata. Vertical distribution of soil carbon was quantified along with other chemical and physical soil properties that affect rice production in Parrita, Costa Rica. A map of spatial prediction of the distribution and goodness-of-prediction values were calculated to estimate the effectiveness of the SCS prediction when different numbers of sampling points were used 45, 27, 15 and 7 microplots. As accurate measurements, the Mean Absolute Error and the Mean Square Error were calculated. In this study, the SCS was 85.8 (±2.6) Mg C ha-1, into the total profile (0-100 cm), where the first 30 cm represented 46.2%. Prediction of the spatial distribution suggests that in annual agricultural crops, with tillage systems 15 sampling points ha-1 a can effectively estimate the SCS.

RESUMEN. Introducción: El biocarbón es un material carbonoso con potencial para mejorar la fertilidad de los suelos y contribuir a la sostenibilidad agrícola. Sus propiedades fisicoquímicas dependen tanto de la biomasa empleada como de las condiciones de producción. En Costa Rica, cultivos como café y palma africana generan grandes volúmenes de residuos lignocelulósicos con escaso aprovechamiento, lo que representa una oportunidad para su transformación en biocarbón. Objetivo: Evaluar el efecto del tipo de horno en la producción de biocarbón a partir de madera de ciprés (Cupressus sp.), pinzote de palma africana (Elaeis guineensis) y bambú (Guadua angustifolia), sobre las propiedades físicas y químicas. Métodos: Elaboramos biocarbones en un horno abierto de campo tipo “Kon Tiki” y en un horno de laboratorio tipo mufla bajo condiciones controladas. Caracterizamos los materiales mediante análisis proximal, determinación de cenizas, pH y conductividad eléctrica. La capacidad de adsorción la evaluamos mediante las pruebas de azul de metileno y número de yodo, el área superficial y la porosidad total la estimamos con el método BET. Resultados: Observamos diferencias significativas entre los biocarbones según la biomasa y el tipo de horno. Los biocarbones producidos en campo presentaron valores más altos de pH, conductividad eléctrica y cenizas, propiedades asociadas a una mayor capacidad de intercambio catiónico, pero a una menor homogeneidad estructural. En contraste, los biocarbones de laboratorio mostraron mayor contenido de carbono fijo, menor fracción de compuestos volátiles y mejor desarrollo textural, reflejado en áreas superficiales y porosidades totales superiores. El índice de yodo fue consistentemente mayor que la adsorción de azul de metileno, lo que confirma la predominancia de la fracción microporosa. Conclusiones: Tanto la biomasa como el tipo de horno influyen de manera determinante en las propiedades del biocarbón, que condicionan su desempeño como enmienda agrícola.