Abstract. The ‘soils of the anthropocene’ are predominately agricultural. To understand them, we analysed agri- and silvicultural intensification of Uruguayan grasslands in a country wide survey on fertility proxies, pH and trace metals in topsoils originating from different land uses. We observed a loss of nutrients, trace metals and organic matter from grassland, crops and timber plantations, and its accumulation in the topsoils of riverine forests. The translocation of nutrients and organic matter across the landscape to the erosion base depends on local land use trajectories. Increasing soil acidification is driving a positive feedback loop, and land use intensification is leading to degradation of local black soils within a few decades. Our data raises questions about the resilience and carrying capacity of Uruguayan soils with regard to currently implemented highly productive management forms, including the use of timber plantation for carbon sequestration, and supports more conservative forms of extensive management on the grassland biome.
Recycling nutrients is essential for closing nutrient loops within a circular economy. Using locally available resources such as human excreta to produce bio-based recycling fertilizers can substitute mineral fertilizers and thereby promote environmentally friendly food production. To better understand the fertilizer potential and nitrogen value of human excreta, three novel and safe recycling products were evaluated in a field experiment. Two nitrified urine fertilizers (NUFs) and one fecal compost were applied alone or in combination, and compared against the commercial organic fertilizer vinasse. In addition, the uptake of pharmaceuticals was assessed for treatments with compost application. White cabbage (Brassica oleracea var. capitata f. alba) was cultivated in plots in three different soil types (sand, loam or silt) treated with the fertilizers according to plant needs and mineral soil nitrogen content. The two NUFs resulted in marketable yields similar to those of vinasse in all soil types. Combining fecal compost with a NUF led to increased marketable yield compared to compost alone. The highest yield was recorded from the sandy soil, where vinasse and NUF treatments led to comparable yields, as expected in organic productions systems (up to 72 t ha−1). The cabbage yield and total aboveground fresh biomass followed the following trend in all soils: NUFs ∼ vinasse ≥ compost + NUF ≥ compost. Nitrogen uptake in the cabbage heads and total biomass was significantly higher in sand (69.5–144 kg ha−1) than loam (71.4–95.8 kg ha−1). All compost treatments alleviated the effect of soil type and resulted in comparable nitrogen uptake and yield in all soil types. Plant uptake of pharmaceuticals (Carbamazepin) was higher in sand than in loam, and concentration in the edible part was lower than in the outer leaves. In conclusion, NUF alone appears to be a promising successful fertilizer substitute in horticultural food production. The combined application of NUF and compost led to slightly lower crop yields, but may increase soil carbon content in the long term, promoting climate-friendly food production.
Abstract. The “soils of the Anthropocene” are predominately
agricultural. To understand them, we analyzed agri- and silvicultural
intensification of Uruguayan grasslands (GLs) in a country-wide survey on
fertility proxies, pH and trace metals in topsoils originating from
different land uses across the whole country. Thus, our results reflect
interactions of both the natural diversity of Uruguayan soil formation
and the impacts of land use change. We observed a loss of nutrients, trace
metals and organic matter from GLs, croplands and timber plantations (TPs). As
an example, the cation exchange capacity was 160 % higher in native
forests (NFs) compared to GLs and lowest in TPs, reaching
only half of the cation exchange capacity (CEC) in GLs. Acidification of topsoils continues as
three-fourths of all samples are “extremely acidic” and “very strongly
acidic”. Topsoils of riverine forests accumulate more trace metals compared
to the other uses. We assume an accumulation in the topsoils of riverine
forests, where high levels of nutrients, trace metals and organic carbon (OC) are
found. The translocation of nutrients and organic matter across the
landscape to the erosion base depends on local land use trajectories.
Increasing soil acidification is driving a positive feedback loop, and land
use intensification has lead to degradation of local black soils within a
few decades. Our data raise questions about the resilience and carrying
capacity of Uruguayan soils with regard to currently implemented highly
productive management forms, including the use of TPs for
carbon sequestration, and supports more conservative forms of extensive
management on the GL biome.
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