Phillip E. Speth

Nitrogen and phosphorus availability from liquid dairy manure to potatoes

The effective use of manure nutrients requires an accurate assessment of their availability to the specific crops being grown. A fertilizer equivalence approach was used to evaluate the availability of nitrogen (N) and phosphorus (P) from liquid dairy manure to potatoes in field experiments conducted in northeast Wisconsin in 2000, 2001, and 2002. Crop responses to moderate and high rates of liquid dairy manure (93,500 and 187,000 L ha−1) were compared to results obtained from N or P fertilizer applied at five rates (0 to 269 kg ha−1). Availability estimates were made using the fertilizer equivalence method based on tuber yield, harvested tuber N or P concentration and uptake, petiole nitrate or total P concentration, and soil nitrate or extractable P phosphate levels. Results showed an apparent availability of manurial N from 10% to 40%, with an overall average across all 3 years and all parameters of 28.6% for the lower rate and 24.6% for the high rate. These values are slightly less than average availability measured where corn has been used as the test crop. Although all parameters did not show responses to P fertilizer additions in these trials, where estimates were possible, P availability ranged from 20% to 90% with an overall average across all 3 years of 55.4% for the low and 50.5% for the high manure rates. Despite potato being more shallow-rooted and somewhat less efficient in N and P use compared to corn, it appears that only minor adjustments to manurial nutrient availability estimates are warranted when potatoes are grown.ResumenEl uso eficiente de los nutrientes presentes en el abono requiere de una evaluación acertada de su disponibilidad a los distintos cultivos. Para evaluar la disponibilidad de nitrógeno (N) y de fósforo (P) de un estiércol líquido de bovino en experimentos de campo en el noreste de Wisconsin en los años 2000, 2001 y 2002 se usó un enfoque sobre equivalencia del fertilizante. Las respuestas del cultivo a dosis moderada y alta (93,500 y 187,000 L/ha−1) se compararon con los resultados de fertilizante a base de N o de P aplicado a cinco dosis (0 a 269 Kg/ha−1). Los estimados de disponibilidad fueron hechos utilizando el método de equivalencia del fertilizante basado en rendimiento de tubérculos, concentración y absorción de N o P del tubérculo cosechado, contenido de nitrato en el pecíolo o concentración total de P, y niveles de fosfato o nitrato extraíbles del suelo. Los resultados mostraron una aparente disponibilidad de nitrógeno de 10% a 40% proveniente del estiércol con un promedio total en los tres años y todos los parámetros de 28.6% para la dosis más baja y 24.6% para la dosis más alta. Estos valores son ligeramente menores que el promedio de disponibilidad medido en un cultivo de maíz usado como testigo. Aunque no todos los parámetros en estos ensayos mostraron respuesta a la adición de fertilizante fosforado donde fue posible el estimado, la disponibilidad de fósforo varió de 20% a 90%, con un promedio en los tres años de 55.4% para el más bajo y 50.5% para las dosis de estiércol más altas. A pesar de que la papa enraíza más superficialmente y es algo menos eficiente en la utilización de N y P comparado con el maíz, parece que sólo se necesitan ajustes menores para que la disponibilidad de nutrientes del estiércol se garanticen cuando se cultiva papa.

Surfactant use to improve soil water distribution and reduce nitrate leaching in potatoes.

Recent evaluations of soil water use by potato (Solanum tuberosum L.) plants have confirmed that a dry zone develops mid to late in the growing season when potatoes were grown in a ridge and furrow system under sprinkler irrigation on some sandy soils. Although trickle irrigation has been shown to reduce the dry zone in potato hills, a more cost- and labor-effective solution could be the use of a surfactant to change soil water surface tension and thereby promote more uniform water distribution into hills. Water content in surfactant-treated potato hills was compared with no-surfactant-treated hills using data from time domain reflectometry probes collected at 15-minute intervals. In addition, nitrate-nitrogen (NO3−N) concentration in soil water collected 1 m below the crop row with porous cup samplers was evaluated to assess NO3−N leaching below the root zone of potatoes. Data from surfactant applications at 9.35 L ha−1 at planting with the seed piece in 1998, 1999, and 2003 through 2005 generally resulted in significantly increased movement of water into the dry portion of potato hills and in many cases decreased soil water NO3− concentrations at a depth of 1 m beneath potato hills. Comparison of several surfactants suggested that water movement into the dry zone can be accomplished with a number of different products. Some trends of increased potato yield with surfactant applications as compared with no surfactant were noted in a few cases; but in all cases (P = 0.16-0.24), these were not statistically significant at the 95% level.

Alfalfa Yield and Nutrient Uptake as Affected by pH and Applied K

Abstract Approximately 30% of the cultivated cropland in the state of Wisconsin is devoted to alfalfa (Medicago sativa) production. Much of the alfalfa forage produced is used to feed the approximately 1,350,000 dairy cattle found in the state. A key concern of dairy producers is the cation to anion balance in rations for dry and early lactation cows, which is greatly influenced by soil K levels. This study was designed to examine the interactive effects that varying soil pH levels and annual potassium applications would have on forage mineral balance, yield, and quality. Three locations with varying soil textures were used for this 4‐yr study. Results indicate that soil pH and applied K can both significantly influence forage yield, quality, and cation levels. At soil pH levels that are near optimum for alfalfa production and yield levels in the 8–10 Mg ha−1 range, it appears that approximately 224 kg K2O ha−1 is required annually to optimize yield and stand quality and to maintain soil test in the optimum category. At all locations, as soil K increased, tissue K increased, and to a much smaller extent, tissue Ca and Mg decreased. Annual K application resulted in a buildup of soil test K and a decrease in soil test Ca and Mg. Increasing soil pH, and consequently soil test Ca, did not consistently result in reduced tissue K levels. However, liming these acid soils was essential to optimize alfalfa yield. Keeping soil test K levels in the optimum range appears to be the best strategy for keeping forage tissue K levels in acceptable ranges for use as dry cow and early lactation dairy feed.

Fumigation and Fertilizer Nitrogen Source Effects on Potato Yield, Quality, and Early Dying

Research has shown that while fumigation and use of ammonium N can both reduce the severity of verticillium wilt (Verticillium dahliae Kleb.) of potatoes (Solanum tuberosum L.), the use of the two practices together raises concerns over feeding the crop only ammonium N under reduced nitrification conditions. To assess the validity of this concern, we conducted two 3-year field split-plot experiments with both using metam sodium fumigant (none, fall or spring applied) as the main plot. For the first experiment, N source (134 kg N ha−1 as ammonium sulfate, urea, or ammonium nitrate) was the split, whereas for the second trial in-season N rate (0, 67, 134, or 202 kg N ha−1 all as ammonium sulfate) was the split. For both trials, in 2 of the 3 years, fumigation significantly increased tuber yield by an average of 9.9 Mg ha−1 and decreased late-season verticillium severity ratings from 77 to 45%. In some years, fumigation also increased the proportion of U.S. No. 1 tubers and tubers >170 g. No differences in crop yield or quality were observed between the various N sources applied. This was true even on spring-fumigated areas with the highest rate of ammonium N applied. These experiments confirm that the choice between in-season potato N fertilizer should be based on factors such as potential for benefits or N losses, cost, and convenience of use rather than concern over an interaction between fumigation and ammonical N. While both fumigation and N rate reduced verticillium severity ratings in some years, the lack of interaction suggests these factors are functioning independently.ResumenLa investigación ha demostrado que tanto la fumigación como el uso de N amoniacal pueden reducir la severidad de la marchitez por verticillium (Verticillium dahliae Kleb) de papa (Solanum tuberosum L.). El uso de dos prácticas juntas llama la atención sobre la alimentación del cultivo solo con N amoniacal bajo condiciones de nitrificación reducida. Para analizar la validez de esta preocupación, desarrollamos dos experimentos de tres años de parcelas divididas, con el uso del fumigante metam sodio (sin aplicación, aplicado en el otoño, o en la primavera), como la parcela principal. Para el primer experimento, la fuente de N (134 Kg N ha-1 como sulfato de amonio, urea, o nitrato de amonio) fue la parcela chica, mientras que para el segundo ensayo, el nivel de N durante el ciclo (0, 67, 134, o 202 Kg N ha-1 todo como sulfato de amonio) fue la parcela chica. Para ambos ensayos, en dos de los tres años, la fumigación aumentó significativamente el rendimiento de tubérculo en un promedio de 9.9 Mg ha-1 y disminuyó las calificaciones de severidad de Verticillium al final del ciclo de 77 a 45%. En algunos años, la fumigación también aumentó la proporción de tubérculos U.S. No. 1 y de tubérculos de >170 g. No se observaron diferencias en rendimiento o calidad del cultivo entre las diversas fuentes de N aplicadas. Esto siguió siendo cierto aun en áreas fumigadas en la primavera con la aplicación del nivel más alto de N amoniacal. Estos experimentos confirman que la decisión entre la fertilización nitrogenada durante el ciclo debería basarse en factores como el potencial de beneficios, o en pérdidas de N, costos, en la conveniencia del uso, en vez de la preocupación sobre una interacción entre fumigación y N amoniacal. Mientras que tanto la fumigación como el nivel de N redujeron las lecturas de severidad por Verticillium en algunos años, la falta de interacción sugiere que estos factores están funcionando independientemente.

Effectiveness of ACA rates on potatoes raised in irrigated sandy soil.

Over a 5-year period, field evaluations of several rates of ACA, an acronym for Agricultural Crop Additive, were conducted on irrigated sandy Wisconsin soils using potato (Solanum tuberosum L.) as the test crop. In some years, statistically significant tuber total yield increases of about 4 Mg ha−1 were seen for one rate, but not others, with the response rate varying between years. In 1 year, similarly sized yield increases were seen for all rates. In most years, the use of ACA (at one or more rates) increased the size of harvested tubers but did not affect other measured growth parameters including stem or tuber number, early-season vegetative or root growth, or midseason leaf nutrient concentrations. In the year when ACA was evaluated across three potato varieties, the responses appeared to be variety specific. No clear mode of action could be identified where the positive responses were seen other than the apparent influence of the additive on harvested tuber size.