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The conversion of bio-wastes to useful products such as biochar provide a suitable option not only to minimize the mass of wastes, but also to use the biochar as soil amendment. In the present study, food waste biochar (FWB) and agricultural waste derived biochar (AB), either alone or in combination (FWB + AB), were tested for their effects on soil microbiological characteristics (soil enzymes, soil basal as well as substrate-induced respiration), plant growth and photosynthetic parameters. Four treatments were tested: control, FWB, AB and FWB + AB. The results indicated that the application of AB significantly enhanced the plant above ground and below ground fresh and dry biomass as compared to other amendments and control (+41 to +205% compared to control). The application of FWB enhanced the quantum yield of photosystem II (QY-max, +4% compared to control) and normalized difference vegetation index (NDVI, +13% compared to control). Moreover, the FWB application improved the soil dehydrogenase (DHA) activity (+24% compared to control). Furthermore, the soil basal respiration was found to be increased under AB application (+46% compared to control) and the substrate-induced respirations were relatively decreased, depicting negative effects of applied biochars on substrate-induced respirations. Thus, we concluded that the differential responses of observed crop and soil attributes might be related to the biochar specific effects on soil properties. [ABSTRACT FROM AUTHOR]

Miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice productivity and water use efficiency (WUE) after biochar application in Costa Rica. The field flights were conducted over two experimental groups with bamboo biochar (BC1) and sugarcane biochar (BC2) amendments and one control (C) group without biochar application. Rice canopy biophysical variables were estimated by inverting a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary productivity (GPP) and WUE across treatments were estimated using light-use efficiency and WUE models respectively from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration rate. We found that GPP was increased by 41.9 ± 3.4% in BC1 and 17.5 ± 3.4% in BC2 versus C, which may be explained by higher soil moisture after biochar application, and consequently significantly higher WUEs by 40.8 ± 3.5% in BC1 and 13.4 ± 3.5% in BC2 compared to C. This study demonstrated the use of hyperspectral and thermal imagery from a drone to quantify biochar effects on dry cropland by integrating ground measurements and physical models. [ABSTRACT FROM AUTHOR]