Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project is designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N are spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow the determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Broadcast and Band Phosphorus and Potassium Placement for Corn and Soybean Managed with Till or No Till

No-till minimizes the incorporation of crop residue and fertilizer with soil; resulting in wetter, colder soils and the accumulation of organic matter, phosphorus (P), and potassium (K) near the soil surface. Banding of P and Kcould be more effective than broadcast fertilization by counteracting stratification, applying nutrients in the root zone (starter effect), and minimizing reactions with the soil that may reduce their availability to plants. Therefore, a long-term study was established in 1994 to evaluate P and K fertilizer rates and placement methods for grain yield of corn and soybean managed with no-till and chiselplow/disk tillage.

Nitrogen Fertilization of Corn Grown with a Cover Crop

Objectives of this project were to study corn nitrogen (N) fertilization requirement and corn-soybean yield response when grown in a rye cover cropping system. Multiple rates of N fertilizer were 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 was conducted at multiple research farms, with the intent for comparison of with and without a cover crop system across varying soil and climatic conditions in Iowa.

Long-term Evaluation of Hybrid, Nitrogen, and Potassium Interactions in Continuous Corn

A long-term experiment was established in 2009 to study continuous corn responses to potassium (K), nitrogen (N), and hybrid rootworm resistance. Previous research suggested a need for this study. A long-term trial conducted until 2001 at the ISU Northern Research Farm showed that the maximum corn yield level and the N rate that maximized yield was higher when K was optimal or greater. In contrast, the relative yield response to N and the N rate that maximized yield were similar for soil-test phosphorus (P) levels ranging from very low to very high. Other studies have shown that rootworm resistance often increases yield compared with untreated susceptible hybrids. Also, that rootworm resistance does not consistently affect the K rate that maximizes yield, but increases K removal because of the higher yield levels. Therefore, this new study evaluates possible interactions between rootworm resistance and N and K fertilization in corn.

Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project was designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N were spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow the determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Phosphorus and Potassium Rates and Placement Methods for Corn and Soybean Managed with No-till or Tillage

No-till management for corn and soybean results in little or no incorporation of crop residues and fertilizer with soil. Subsurface banding phosphorus (P) and potassium (K) fertilizers with planter attachments could be more effective than broadcast fertilization, because in no-till with broadcast fertilizer, both nutrients accumulate at or near the soil surface. A long-term study was initiated in 1994 at the ISU Northwest Research Farm to evaluate P and K fertilizer placement for corn and soybean managed with no-till and chiselplow tillage.

Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project was designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N were spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Placement Methods of Phosphorus and Potassium for Corn and Soybean Managed with No-till and Chisel-plow/Disk Tillage

No-till management limits the incorporation of crop residue and fertilizer with soil resulting in wetter, colder soils and the accumulation of organic matter, phosphorus (P), and potassium (K) near the soil surface. Banding of P and K could be more effective than broadcast fertilization by counteracting stratification, applying nutrients in the root zone (starter effect), and minimizing reactions with the soil that may reduce their availability to plants. Therefore, this long-term study was established in 1994 to evaluate P and K fertilizer placement methods and grain yield of corn-soybean rotations managed with notill and chisel-plow/disk tillage.

Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project was designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N were spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow the determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Radiocarbon, isotope, biogenic, and 230Th measurements for sediment core RC10-196

The subarctic North Pacific Ocean holds a large CO2 reservoir that is currently isolated from the atmosphere by a low-salinity layer. It has recently been hypothesized that the reorganization of these high-CO2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation. This reorganization would leave some imprint on paleo-productivity records. Here we present 230Th-normalized biogenic fluxes from an intermediate depth sediment core in the Northwest Pacific (RC10-196, 54.7°N, 177.1°E, 1007 m) and place them within the context of a synthesis of previously-published biogenic flux data from 49 deep-sea cores north of 20°N, ranging from 420 to 3968 m water depth. The 230Th-normalized opal, carbonate, and organic carbon fluxes from RC10-196 peak approximately 13,000 calendar years BP during the Bølling/Allerød (B/A) period. Our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period, increased somewhat in the Northwest Pacific during Heinrich Event 1, and reached a maximum across the entire North Pacific during the B/A period. We evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the North Pacific, including changes in preservation, sediment focusing, sea ice extent, iron inputs, stratification, and circulation shifts initiated in the North Atlantic and North Pacific. Our analysis suggests that while micronutrient sources likely contributed to some of the observed changes, the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region-wide contemporaneous peaks in export production. We argue that paleo-observations are most consistent with ventilation increases in both the North Pacific (during H1) and North Atlantic (during B/A) being the primary drivers of increases in biogenic flux during the deglaciation, as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline.

Influencia de la fertilización y el riego sobre aspectos cuali-cuantitavos de la reproducción de cebolla (Allium cepa L.) para la industria del deshidratado

La creciente demanda, en los últimos años, a nivel mundial y nacional de los productos deshidratados hace que esta actividad se perfile como promisoria en la región cuyana. Prácticamente el 100 % de la deshidratación de cebolla (Allium cepa L.) del país se realiza en Mendoza, habiendose hecho sólo producciones aisladas y de escaso volúmen en otras plantas del país. Las estimaciones preveen que se seguirá abasteciendo el mercado local y se incrementaránlas exportaciones de cebolla deshidratada. El objetivo general del presente trabajo fue establecer la influencia de la fertilización y el riego sobre la productividad y calidad de un cultivar mejorado de cebolla de importancia económica para la industria del deshidratado. En el Campo Experimental del INTA La Consulta se llevaron a cabo durante los años 1994-´95 y 1995-´96, dos ciclos de ensayos, con una línea de cebolla para deshidratar derivada del cultivar Southport White Globe. El suelo es de origen aluvial, profundo y de textura franca (Torrifluvente típico). Se determinaron los principales parámetros físicos, químicos e hídricos de la fracción fina del suelo. Para determinar el efecto de la fertilización sobre componentes de crecimiento y calidad y estudiar la variación de la concentración y ritmo de absorción de nutrimentos se ensayaron diferentes tratamientos. En el primer ciclo se ensayaron nueve tratamientos con tres niveles de N (0, 100, 200 kg N ha-1 ) aplicado como urea y tres niveles de P (0, 30, 60 kg P ha-1 ) como superfosfato. En el segundo ciclo se probaron ocho tratamientos con los siguientes niveles de N, P y K, respectivamente: (0 y 100 kg N ha-1), (0 y 40 kg P ha-1) y (0 y 60 kg K ha-1), éste último como sulfato de potasio. Para evaluar el efecto de diferentes regímenes de riego al final del ciclo de cultivo sobre la produccción cuantitativa y cualitativa de cebolla para la industria del deshidratado se programaron cortes anticipados de riegos, según diferentes fechas anteriores a la cosecha. Estas fueron para el primero y segundo ciclo de ensayo, respectivamente: (33, 27, 21, 8) y (21,14, 7) días anteriores a la fecha de cosecha estimada. Las principales conclusiones fueron: A) Con respecto a la fertilización: i) En todos los casos, e independientemente del tratamiento ensayado el mayor incremento relativo de sustancia seca aérea se evidencia durante la II fase de viii desarrollo que tiene lugar entre los primeros días de noviembre y mediados de diciembre ii) En dicha II fase se comienzan a manifestar incrementos absolutos de peso seco aéreo y área foliar atribuibles a la fertilización iii) También en todos los tratamientos se verifica que al finalizar la II fase el peso de los bulbos alcanza el 20 % de su peso de cosecha. En ese momento, los valores determinados para el porcentaje de sólidos totales (% ST) oscilan entre 13 % y 14 % iv) La mayor tasa de crecimiento del bulbo se constató en la III fase en la que se logra el 80% restante de su peso final v) En la III fase el % ST del bulbo sigue en aumento hasta casi el momento de cosecha y alcanzó valores promedios de 20 % y 21 %. La fertilización con diferentes dosis de N, P y K no influyó en el contenido de materia seca de los bulbos aunque sí lo hizo positivamente sobre su peso fresco vi) Los máximos rendimientos de bulbos (37.3 Mg ha-1) y de materia seca (7.92 Mg ha-1) se obtuvieron, en el segundo ciclo de ensayo, con las dosis de 100 kg N ha-1 y 40 kg P ha-1 vii) Los parámetros tisulares aéreos de valor diagnóstico asociados a máximosrendimientos, y al final de la II fase, correspondieron a una Alimentación Global (N, P, K) de 4.96 g % g s. seca y concentraciones de N, P y K respectivamente de: 2.56 g %, 0.22 g % y 2.18 g %. En cuanto a los tenores de Ca y Mg los porcentajes respectivos fueron: 2.10 g % y 0.16 g %. Los valores medios de equilibrios nutricionales fueron: N - P - K: 52 % - 4% - 44%. Con respecto a los micronutrimentos sus concentraciones fueron, en mg kg-1, Fe: 400, Zn: 55, Mn: 35 y Cu:19 y los valores de equilibrios nutricionales : 78.5 % - 11 % - 7 % - 3.5 %, respectivamente viii) La extracción total efectuada por el cultivo para esas máximas producciones, en kg ha-1, de N - P - K - Ca - Mg fueron: 214 - 40 -187 - 184 -19 B) Con respecto a los regímenes de riego: i) El rendimiento máximo obtenido -38.9 Mg ha-1- en el ensayo de cortes anticipados de riego correspondió al tratamiento R7 del ciclo 1995-‘96 ii) El mismo perteneció al tratamiento, que además de la fertilización básica con 100 kg N ha-1, aseguró durante los meses de noviembre, diciembre y enero, ix hasta siete días antes de cosecha, una humedad edáfica mínima (umbral de riego) correspondiente al 50 % del agua disponible. Este tratamiento se caracterizó por un total de 18 riegos y una incorporación de agua de 6120 m3 ha-1. iii) Los rendimientos totales de materia seca fueron afectados detrimentalmente por los otros regímenes de riego de cortes más anticipados iv) Se constató una relación lineal positiva altamente ignificativa entre el rendimiento y la lámina total de agua aplicada al cultivo.

Influence of fertilization on the growth of radicchio "Rosso di Chioggia" cultivated in two different environments

Este trabajo evalúa la influencia de la fertilización en radicchio tipo "Rosso de Chioggia" (precocidad media) sobre algunos índices de crecimiento. Se realizaron ensayos durante dos campañas en Rovigo (Italia) y una en Mendoza (Argentina), aplicándose dosis crecientes de NPK, identificadas como N0P0K0, N1P1K1, N2P2K2, en Mendoza y en Rovigo, además, N3P2K2. Durante el cultivo se calcularon índices de crecimiento como: relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA), leaf weigh ratio (LWR), crop growth ratio (CGR), leaf area index (LAI) and leaf area duration (LAD). En Mendoza, el CGR estuvo fuertemente influenciado por NAR desde el trasplante hasta alcanzar 776 grados días (GDD); desde 1052 a 1653 GDD el CGR fue afectado por el LAI el cual aumentó marcadamente debido a las condiciones ambientales favorables. Entre los 1052 y 1653 GDD el incremento del LAI determinó una reducción en la eficiencia fotosintética. En Rovigo, la tendencia de los índices fue disímil en los dos años, encontrándose respuestas diferentes en LAR y en SLA. En el segundo año, el CGR siempre arrojó valores más altos, mientras que NAR no difirió en ninguno de los años. En la segunda mitad del ciclo, CGR estuvo fuertemente asociado a una menor eficiencia fotosintética, debido a la formación de la cabeza. Valores elevados de LAI indicaron una extensión del ciclo, retrasando la formación de la cabeza. Las plantas alcanzaron la madurez comercial con LWR entre 0,35 - 0,40 g g-1. En ambos ambientes, no se observó claramente el efecto de la fertilización sobre los índices; si bien las dosis más altas mostraron mayor actividad de crecimiento en las etapas tempranas.

Effect of compost and slow-release fertilizers addition on soil biochemistry and yield of maize (Zea mays L.) in Oaxaca, Mexico

The effect of Bokashi (B, a fermented compost), slow-release fertilizers (SRFs) and their combined application on mycorrhizal colonization (MC), soil invertase, cellulase, acid (AcP) and alkaline (AlP) phosphatases activities and maize (Zea mays L.) yield was investigated in terrace (TS) and valley (VS) soils in Oaxaca, Mexico. A complete randomized design, seven fertilizer treatments and four replications were used: unamended control (C); conventional fertilization (90-46-00 NPK) (CF); B; SRF1 (Multigro 6®, 21-14-10 NPK); SRF2 (Multigro 3®, 24-05-14 NPK); B+SRF1; B+SRF2. Highest root colonization percentage: CF in VS, and SRF2 in TS. Highest extraradical mycelium length: B, B+SRF1, CF in VS, and B+SRF1 in TS. In both soils, B increased the spore number. Highest AcP activity: B, SRF2 in VS, and B+SRF1, B+SRF2 in TS. Highest AlP activity: B+SRF1, CF in VS, and C in TS. Highest invertase activity: B+SRF1, SRF2, CF in VS, and B in TS. Grain yield only increased with B in VS. The significant interaction soil type × fertilizer treatment for the majority of the biological soil properties analyzed suggests that MC and soil enzyme activity response to fertilization was influenced by soil type. Bokashi, alone or combined with SRFs improves biological soil fertility in maize fields.