Thesis Chapters by Jose L . Pantoja
TESIS DE INGENIERIA, 2005
La compactación es la pérdida de la porosidad del suelo. Un horizonte compacto se puede formar po... more La compactación es la pérdida de la porosidad del suelo. Un horizonte compacto se puede formar por el uso de equipos que laborean el suelo a la misma profundidad y/o el pisoteo animal, lo que ocasiona pérdida de la estructura, profundidad efectiva, drenaje interno, aumento en la densidad aparente y mayor resistencia a la penetración de raíces. La profundidad efectiva se mejora al romper las capas compactas mediante el subsoleo. Zamorano mantiene sus sistemas productivos en suelos con horizontes compactos que limitan el crecimiento radicular, por ello existe el interés de evaluar el efecto de la recuperación de estos suelos. Se evaluó el efecto del subsoleo en el acondicionamiento de las propiedades físicas, su efecto en las propiedades químicas y el efecto en el rendimiento de maíz (Zea mays L. cv. Dekalb D-343 y cv. HB 104), cebolla (Allium cepa L. cv. Granex 429), pasto Estrella (Cynodon nlemfuensis) y sorgo forrajero (Sorghum bicolor L. cv. Sureño) en tres áreas. Se utilizó un tractor de 135 HP para labrar la mitad del área con un subsolador de dos cinceles provisto de aletas; el espaciamiento de subsoleo y su profundidad potencial de penetración en el suelo fueron de 75 y 60 cm, respectivamente. Se realizaron dos pases, el primero paralelo a la pendiente y el segundo a 45º del primero. La eficiencia neta del subsoleo fue < 70% en las tres áreas porque el tractor utilizado no tuvo la capacidad para fracturar el suelo a la profundidad requerida. El subsoleo mejoró la profundidad y el volumen de raíces e incrementó el flujo vertical de agua y el lavado de nutrientes, lo cual redujo el pH del suelo, la materia orgánica (MO), P, Ca, y Mg, mientras que el K, Cu, Fe, Mn, y Zn se encuentran en mayor concentración en el área con subsoleo. El N se encuentra en guales concentraciones en los dos tratamientos. Los análisis foliares no mostraron diferencia de absorción de nutrientes. El subsoleo mejoró la productividad de mazorca con tuza en el maíz Dekalb D-343, pero presentó un menor desempeño en la producción de mazorca sin tuza en el maíz Dekalb D-343, materia fresca (MF) en el pasto Estrella (primer corte) y materia seca (MS) en el maíz Dekalb D-343, pasto Estrella y sorgo forrajero (primer corte). No se observaron diferencias en la producción de cebolla Granex 429, MF en el maíz Dekalb D-343, pasto Estrella (segundo corte) y sorgo forrajero (primer y segundo corte), MS en pasto Estrella y sorgo forrajero (segundo corte) ni en la producción de mazorcas con y sin tuza en el maíz HB 104. Para alcanzar una eficiencia óptima en el subsoleo es necesario utilizar un tractor de mayor potencia para alcanzar la profundidad de fractura esperada.
Papers by Jose L . Pantoja
This Conference Proceeding is brought to you for free and open access by the Agronomy at Digital ... more This Conference Proceeding is brought to you for free and open access by the Agronomy at Digital Repository @ Iowa State University. It has been
La arveja (Pisum sativum L.) es importante para la alimentacion y economia de los agricultores de... more La arveja (Pisum sativum L.) es importante para la alimentacion y economia de los agricultores de Ecuador, pero no hay suficientes informacion de fertilizacion de este cultivo. Se evaluo la respuesta de la rveja, var. INIAP 436 Liliana, a la fertilizacion fosforica (FP) y fertilizacion nitrogenada (FN). La investigacion se ejecuto entre Mayo y Sept. de 2014 en Ambuela, Perucho, Quito, Pichincha, Ecuador. Se aplico P porque el analisis inicial de suelo reflejo niveles bajos de P. La siembra se realizo a 0.60 m entre surcos y 0.40 m entre postura (5 semillas postura-1). Se utilizo un diseno de parcelas divididas en un arreglo de bloques completos al azar (cuatro replicas), donde cada parcela tuvo surcos de 8 m de largo. Los niveles de FP (0 y 20 kg ha-1) fueron la parcela principal y los de FN (0 a 150 kg ha-1 con incrementos de 30 kg) las sub-parcelas. Se utilizo urea y roca fosforica para los tratamientos y una dosis de 30 kg K ha-1 como muriato de K. Al inicio del llenado de vaina...
Nitrogen (N) fertilizer inputs for intensive corn-based cropping systems can increase nitrate (NO... more Nitrogen (N) fertilizer inputs for intensive corn-based cropping systems can increase nitrate (NO3- –N) concentrations in groundwater. Nitrogen transport in surface water to the Gulf of Mexico is also an on-going issue for the upper Mississippi river basin, especially areas with large corn and soybean acreage. Education and policy efforts have focused on improvement in N
Producers have many choices of diverse tillage practices for their corn (Zea mays L.) production ... more Producers have many choices of diverse tillage practices for their corn (Zea mays L.) production systems. However, no-till has become an important soil management practice to help reduce water and wind erosion, as well as nutrient runoff, while conserving soil moisture for crop use. No-till systems also help farmers by saving labor and time, as well as reducing farm costs due to
Environmental Modelling and Software, 2014
ABSTRACT The ability of biogeochemical ecosystem models to represent agro-ecosystems depends on t... more ABSTRACT The ability of biogeochemical ecosystem models to represent agro-ecosystems depends on their correct integration with field observations. We report simultaneous calibration of 67 DayCent model parameters using multiple observation types through inverse modeling using the PEST parameter estimation software. Parameter estimation reduced the total sum of weighted squared residuals by 56% and improved model fit to crop productivity, soil carbon, volumetric soil water content, soil temperature, N2O, and soil NO3- compared to the default simulation. Inverse modeling substantially reduced predictive model error relative to the default model for all model predictions, except for soil NO3- and NH4+. Post-processing analyses provided insights into parameter–observation relationships based on parameter correlations, sensitivity and identifiability. Inverse modeling tools are shown to be a powerful way to systematize and accelerate the process of biogeochemical model interrogation, improving our understanding of model function and the underlying ecosystem biogeochemical processes that they represent.
Objectives of this project were to study corn nitrogen (N) fertilization requirement and corn-soy... more Objectives of this project were to study corn nitrogen (N) fertilization requirement and corn-soybean yield response when grown in a cover crop system. Multiple rates of N fertilizer are applied, with measurement of corn yield response to applied N and soybean yield with and without a fall planted winter rye cover crop. The study is being conducted at several research farms, with the intent for study across multiple years to allow comparison of with and without a cover crop system across varying soil and climatic conditions.
Demand for corn (Zea mays L.) stover is increasing for livestock consumption and bioenergy produc... more Demand for corn (Zea mays L.) stover is increasing for livestock consumption and bioenergy production. Frequent stover harvest (SH) from fields to meet these needs could impact crop N availability and soil N cycling. A three year study was conducted at two sites in Iowa with continuous corn (CC) to determine the effect of SH rate and tillage system on corn production, response to N fertilization, and optimal N rate. Treatments were 0, 50, and 100% SH, chisel plow tillage and no-tillage, and six N rates from 0 to 280 kg N ha-1. Profile soil NO3-N concentrations (with no N fertilization) slightly increased from spring preplant to early June with no SH, but were the same with SH post-harvest. Mid-vegetative corn canopy normalized difference vegetative index (NDVI) sensing values were greatest with chisel plow, SH, and N application. The increase in NDVI with SH was less with chisel plow than with no-tillage. Corn grain yield was 9% (0.84 Mg ha-1) greater with chisel plow than 6 with no-tillage. At the economic optimum N rate (EONR), yield was not influenced by SH with chisel plow, but was 6% greater with each SH rate in no-tillage. The EONR was the same with both tillage systems, but decreased by 22 and 45 kg N ha-1 with 50 and 100% SH, respectively. The greater yield with SH resulted in greater grain N utilization GNU. Results indicate N fertilization should be adjusted with SH in CC.
Proceedings of the Integrated Crop Management Conference
Proceedings of the Integrated Crop Management Conference
Communications in Soil Science and Plant Analysis, 2016
Soil Science Society of America Journal, 2015
All Rights reserved. Corn Nitrogen Fertilization Requirement and Corn-Soybean Productivity with a... more All Rights reserved. Corn Nitrogen Fertilization Requirement and Corn-Soybean Productivity with a Rye Cover Crop Nutrient Management & Soil & Plant Analysis winter rye (Secale cereale l.) cover crop (rcc) has potential to reduce no 3-n loss from corn (Zea mays l.) and soybean [Glycine max (l.) Merr.] fields. However, rcc effects on annual crop productivity and corn optimal n fertilization requirement are unclear. the objectives were to evaluate corn and soybean yield response to rcc and corn optimal n rate. treatments were no-rcc and rcc with six fertilizer n rates (0-225 kg n ha-1) applied to corn in a no-till corn-soybean (cs) rotation at four iowa sites in 2009 through 2011. the rcc biomass and n uptake was low, with a maximum of 1280 kg dry matter (dM) ha-1 and 26 kg n ha-1 , respectively. in the no-n control, the rcc reduced soil profile no 3-n by 15 kg n ha-1 only at time of rcc control before corn planting. corn canopy sensing, plant height, and plant population indicated more n stress, reduced plant stand, and slower growth with rcc. the rcc reduced corn grain yield by 6% at the economic optimum n rate (eonr). the eonr was the same with no-rcc and rcc, but plant n uptake efficiency (Pue) was reduced at low n rates with rcc, but not above the eonr. soybean yield was not affected by rcc. results indicate n fertilization rate should be the same with or without rcc. improvement in rcc systems and management could make rcc a more viable practice within notill corn and soybean production.
Soil Science Society of America Journal, 2015
Demand for corn (Zea mays L.) stover is increasing for livestock and bioenergy production. Excess... more Demand for corn (Zea mays L.) stover is increasing for livestock and bioenergy production. Excessive stover harvest (SH) could impact crop productivity and soil N cycling. A 3-yr study was conducted at two Iowa sites with continuous corn to determine the effect of SH level and tillage system on grain yield, response to N fertilization, and optimal N rate. Treatments were none, partial, and complete SH, chisel plow tillage and recently implemented no-till, and six N rates from 0 to 280 kg N ha −1. Profile soil NO 3-N concentration (with no fertilizer N) increased slightly from spring preplant to early June only with no SH but were the same with all SH levels after corn harvest. Corn canopy normalized difference vegetative index (NDVI) values were greatest with both SH levels and chisel plow. Increases in NDVI due to SH was less with chisel plow than no-till. Corn grain yield was 9% (0.84 Mg ha −1) greater with chisel plow than with no-till. At the economic optimum N rate (EONR), grain yield was not influenced by SH with chisel plow but was 6% greater with each SH level under no-till. The EONR was the same with both tillage systems but was 22 and 45 kg N ha −1 lower with partial and complete SH, respectively, than no SH. Results of this study indicate the potential for increased corn yield with SH in a no-till system and a reduced fertilizer N rate requirement with SH regardless of tillage system. Abbreviations: CC, continuous corn; EONR, economic optimum nitrogen rate; GNU 0 , grain nitrogen utilization with no fertilizer nitrogen applied; NDVI, normalized difference vegetative index; NUE, nitrogen use efficiency; PAN, plant-available nitrogen; SH, stover harvest; SOM, soil organic matter; YEONR, yield at the economic optimum nitrogen rate. C orn stover, the vegetative plant material left after grain harvest, accounts for approximately 70% of all crop residue production in the United States (USDOE, 2011). It is an asset for recycling plant nutrients, adding C to soils, and buffering against human and natural disturbances of the soil system (Blanco-Canqui and Lal, 2009). Demand for corn stover is increasing to meet the need for livestock feed and bedding, bioenergy production, and wood replacement in various manufactured products (Sokhansanj et al., 2002). Increasing demand for corn grain and stover for ethanol production has resulted in increased corn acreage in the United States, increased continuous corn (CC) systems, and the potential for continued increase of cropland conversion to corn production (Fixen, 2007; Martin, 2010). If managed inappropriately, SH will lead to increased fertilizer use (Sulc and Tracy, 2007) and, in conjunction with SH, increased potential for negative effects on water quality, nutrient cycling, and soil fertility and productivity (Blanco-Canqui and Lal, 2009). There are both advantages and disadvantages to corn SH. Beneficial effects of SH include faster warming of soils in spring, better seed germination, and less favorable habitat for plant pathogens, while potential adverse effects include higher fluctuations in soil temperature, decline in organic matter and thus degradation
Journal of Environment Quality, 2015
Little information exists on the potential for N fertilizer application to corn (Zea mays L.) to ... more Little information exists on the potential for N fertilizer application to corn (Zea mays L.) to affect N 2 O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N 2 O emissions during subsequent crops in rotation, we measured N 2 O emissions for 3 yr (2011-2013) in an Iowa, corn-soybean [Glycine max (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha-1 , the recommended rate of 135 kg N ha-1 , and a high rate of 225 kg N ha-1); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye (Secale cereale L.) cover crop to interact with N fertilizer rate to affect N 2 O emissions from both crops. The cover crop did not consistently affect N 2 O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N 2 O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0-225 kg N ha-1) did not affect mean N 2 O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N 2 O flux rates from the soybean crops that received 135 and 225 kg N ha-1 N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N 2 O emissions are not easily generalizable. When N fertilizer affects N 2 O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N 2 O emissions are altered or only spread across a greater period of time.
Soil Science Society of America Journal, 2013
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Cover Crop Effects on Nitrous Oxide Emissions: Role of Mineralizable Carbon Soil & Water Management & Conservation T he atmospheric concentration of the potent greenhouse gas N 2 O has increased 40 to 50% since pre-industrial times as a consequence of human activity (Forster et al., 2007). Agricultural soils are the largest anthropogenic source of N 2 O (Smith et al., 2007; Reay et al., 2012). The microbial processes nitrification and denitrification, as well as abiotic processes, produce N 2 O in soils (Venterea et al., 2012). In cultivated soils, denitrification tends to be the dominant process producing N 2 O (Azam et al., 2002; Ostrom et al., 2010). In denitrification, NO 3 is reduced to N 2 O during organic C oxidation in the absence of oxygen (O 2). Nitrous oxide can then be used as an electron acceptor and reduced to N 2 before diffusing from the soil; however, high NO 3 availability inhibits N 2 O reduction (Blackmer and Bremner, 1978; Senbayram et al., 2012). Physical soil conditions such as temperature, texture, and bulk density also influence denitrification and N 2 O emission from the soil surface (Venterea et al., 2012). When these conditions are constant, emission of denitrification-derived N 2 O is controlled by anaerobicity, the availability of NO 3 and mineralizable C substrates, and the amount of N 2 O reduced to N 2 before leaving the soil (Firestone and Davidson, 1989).
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Thesis Chapters by Jose L . Pantoja
Papers by Jose L . Pantoja