Examinando por Autor "Ladd, Brenton"

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Biochar enhances the use efficiency of guano de isla and could boost profitability and food security for smallholders in the global south
(Springer, 2026-06-22) Lukuy Espejo, Sandro Esteban; Cosme De La Cruz, Roberto Carlos; Loret de Mola León, Ursula; Martin Carruitero, Jean Luc; Zavalaga, Carlos; Ladd, Brenton
Guano de isla (seabird guano) is a strategic organic fertilizer in Peru, reserved primarily for economically vulnerable smallholder farmers. However, its availability is declining due to ecological pressures on seabird populations, creating an urgent need to improve its use efficiency. This study tested the hypothesis that biochar can enhance the nutrient use efficiency of guano de isla, allowing reduced application rates without compromising yield or profitability. A randomized complete block experiment (n=10 replicates per treatment) was conducted in sandy soil in Lurín, Peru, to evaluate lettuce (Lactuca sativa) yield under eight fertilization treatments, including inorganic fertilizer (NPK), guano de isla (400 kg ha⁻¹), biochar (3 t ha⁻¹), and combinations thereof. The biochar+guano de isla (BG) treatment applied 200 kg ha⁻¹ of guano de isla (50% of the standard rate). Economic viability was assessed using the value/cost ratio (VCR) under conventional and organic market scenarios, with and without carbon credits. The highest lettuce yields were obtained in the full-rate guano de isla (G) and biochar+guano de isla (BG) treatments, representing a 40% increase compared to the control. Importantly, the BG treatment achieved statistically equivalent yields to the full-rate guano de isla treatment while using 50% less guano de isla. Under conventional market conditions, all treatments resulted in VCR values<1. However, under organic market conditions, the G, BG, and biochar treatments exceeded the profitability threshold (VCR>2), with the BG treatment reaching a maximum VCR of 12.9 when carbon credits were included. These findings demonstrate that biochar can significantly enhance the use efficiency of guano de isla in sandy soils, allowing reduced application rates while maintaining productivity. Integrating biochar with guano de isla could help conserve a strategic national fertilizer resource, improve farm profitability, and strengthen food security for smallholder farmers in the Global South.
Co-benefits of soil carbon protection for invertebrate conservation
(EL SEVIER, 2020-11-13) Flores Rios, Angelli; Thomas, Evert; Peri, Pablo P.; Amelung, Wulf; Duarte Guardia, Sandra; Borchard, Nils; Lizárraga Travaglini, Alfonso Diulio; Vélez Azañero, Armando; Sheil, Douglas; Tscharntke, Teja; Steffan Dewenter, Ingolf; Ladd, Brenton
The global decline in invertebrate diversity requires urgent conservation interventions. However, identifying priority conservation areas for invertebrates remains a significant challenge. We hypothesized that aligning the conservation of invertebrate biodiversity with climate change mitigation ofer offers a solution. As both soil carbon storage and invertebrate biodiversity are positively influenced by plant diversity and productivity, a positive correlation can also be expected between SOC and invertebrate biodiversity. Drawing on >10,000 invertebrate observations organized into functional groups, and site-specific soil organic Carbon (SOC) measurements from Patagonia, the Peruvian Andes, and montane tropical rainforest, we examined the role of climate, soil, topographical position and land use for prediction of invertebrate biodiversity. We found that taxonomic and functional invertebrate diversity and abundance closely correlate with SOC stocks within ecosystems. Topographical position of sites, which was partly associated with SOC, was also important, whereas land use was of subordinate importance. We conclude that recent advances in predicting and mapping SOC can guide the identification of habitats within landscapes with high biodiversity and conservation value for invertebrates. Our findings stress the importance of linking global climate change mitigation initiatives that aim to preserve and restore SOC to efforts aimed at improving the conservation of invertebrates and the ecosystem services they provide, for the realization of mutual climate and biodiversity benefits.
The distribution of cadmium in soil and cacao beans in Peru
(Elsevier, 2023-04-11) Thomas, Evert; Atkinson, Rachel; Zavaleta, Diego; Rodriguez, Carlos; Lastra Paucar, Sphyros Roomel-Luciano; Yovera, Fredy; Arango, Karina; Pezo, Abel; Aguilar Zapata, Javier Neptali; Tames, Miriam; Ramos, Ana; Cruz, Wilbert; Cosme, Roberto; Espinoza, Eduardo; Chavez, Carmen Rosa; Ladd, Brenton
Peru is the eighth largest producer of cacao beans globally, but high cadmium contents are constraining access to international markets which have set upper thresholds for permitted concentrations in chocolate and derivatives. Preliminary data have suggested that high cadmium concentrations in cacao beans are restricted to specific regions in the country, but to date no reliable maps exist of expected cadmium concentrations in soils and cacao beans. Drawing on >2000 representative samples of cacao beans and soils we developed multiple national and regional random forest models to develop predictive maps of cadmium in soil and cacao beans across the area suitable for cacao cultivation. Our model projections show that elevated concentrations of cadmium in cacao soils and beans are largely restricted to the northern parts of the country in the departments of Tumbes, Piura, Amazonas and Loreto, as well as some very localized pockets in the central departments of Huánuco and San Martin. Unsurprisingly, soil cadmium was the by far most important predictor of bean cadmium. Aside from the south-eastern to north-western spatial trend of increasing cadmium values in soils and beans, the most important predictors of both variables in nation-wide models were geology, rainfall seasonality, soil pH and rainfall. At regional level, alluvial deposits and mining operations were also associated with higher cadmium levels in cacao beans. Based on our predictive map of cadmium in cacao beans we estimate that while at a national level <20 % of cacao farming households might be impacted by the cadmium regulations, in the most affected department of Piura this could be as high as 89 %.
Precipitation is the key determinant of topsoil δ15N values in southern Patagonia's semiarid rangelands
(Soil Science Society of America, 2022-02-11) Peri, Pablo L.; Duarte Guardia, Sandra; Amelung, Wulf; Ladd, Brenton
Nitrogen (N) cycling in rangeland soils could potentially be controlled by water supply, stocking rates, or a range of other variables, such as ecosystem N stocks. To gauge the relative importance and elucidate possible interactions among these factors, we measured many abiotic variables to identify first-order controls of δ15N for Patagonia's rangeland soils under contrasting historical grazing intensities. The results showed that δ15N values declined as water availability increased. The effects of precipitation and stocking rate on soil δ15N values were additive, and the effect of precipitation far outweighed the effects of grazing pressure. The soil N stock was a weak predictive variable for modeling variation in δ15N of the soil. Earlier assumptions about an inflection point for N cycling and δ15N values related to aridity were not confirmed. We conclude that variation in water availability drives variation in δ15N values irrespective of grazing intensity. We also conclude that meaningful interpretation of δ15N in soil will require a better mechanistic understanding of the interactions between water and N in the vadose zone than we currently possess.