Examinando por Autor "Contreras, Jose"

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Moderate deficit irrigation improves agronomic performance of quinoa (Chenopodium quinoa Willd.) compared to full irrigation in the central highlands of Peru
(Learning Gate, 2026-03-19) Gavino Lulo, Esthefany Irene; Ccopi Trucios, Dennis; Garcia Seguil, Erika Janina; Requena Rojas, Edilson Jimmy; Contreras, Jose; Solórzano Acosta, Richard Andi; Betega, S.D.; Yaranga, Raúl M.; Pizarro Carcausto, Samuel Edwin
This study evaluated the agronomic performance and water productivity of quinoa (Chenopodium quinoa Willd. cv. INIA 433) under three irrigation regimes in the central highlands of Peru: optimal irrigation (Ks = 1.00), moderate deficit (Ks = 0.66), and severe deficit (Ks = 0.49). The experiment combined constant water table lysimeters and field plots, integrating crop coefficient estimation, water balance analysis, and multispectral monitoring (NDVI, NDRE, SRWI) using UAV imagery and ground spectroradiometry. Moderate water stress (Ks = 0.66) significantly improved reproductive performance, producing approximately 8,000 grains per plant compared with ~3,900 grains per plant under optimal irrigation. Grain protein content increased from 4.8% to 6.0%, while evapotranspiration decreased by 37% (from 374.5 to 234.4 mm), markedly improving water use efficiency. In contrast, optimal irrigation promoted maximum vegetative growth (plant height ~110 cm; NDVI 0.7–0.8) but lower reproductive output, whereas severe stress (Ks = 0.49) reduced yield to 4,400 grains per plant and accelerated senescence. Multispectral indices effectively distinguished water stress levels: NDVI reflected canopy vigor, NDRE detected chlorophyll variation, and SRWI captured plant water status. The results demonstrate that regulated deficit irrigation enhances water productivity and grain quality in quinoa. Maintaining Ks values around 0.65–0.70 appears to optimize yield and resource use efficiency in water-limited Andean agroecosystems.
Trace metals in high-Andean forages: differential dietary exposure in cattle, sheep, and alpacas, and lack of non-carcinogenic risk
(Research Square, 2026-06) Arias Arredondo, Alberto Gilmer; Lopez Rodriguez, Melina; Cruz Luis, Juancarlos Alejandro; Contreras, Jose; Ramos Acuña, Hebert; Solórzano Acosta, Richard Andi
Trace metal accumulation in forage plants is a growing concern in mountain grazing systems, yet the relative importance of environmental and biological drivers remains poorly understood in the high Andes. This study evaluated trace metal concentrations in soils and cultivated forages along an altitudinal gradient (4,098–4,467 m a.s.l.) in the Junín region of central Peru and assessed potential dietary risks for livestock. Soil properties and concentrations of Zn, Cd, Cu, Mn, Pb, and Cr were determined in soils and four forage species (Avena sativa, Dactylis glomerata, Lolium multiflorum, and Lolium perenne) across eight plots. Dietary exposure was estimated using the Estimated Daily Intake (EDI), while non-carcinogenic risks for cattle, sheep, and alpacas were assessed through the Hazard Quotient (HQ) and Hazard Index (HI). Marked spatial variation in soil properties and trace metal concentrations was observed among plots, indicating that metal accumulation was primarily driven by local soil heterogeneity. Altitude was not associated with trace metal concentrations, and forage species showed no significant differences in metal accumulation (p > 0.05). Although sheep exhibited the highest EDI values, all HQ and HI values remained below 1. These findings demonstrate that fine-scale soil heterogeneity is a stronger determinant of trace metal accumulation than altitude or forage species identity in high-Andean forage systems. The study provides new evidence that current trace metal exposure levels do not represent a significant non-carcinogenic risk for cattle, sheep, or alpacas under the evaluated environmental conditions.