Keith A. Kelling

Nitrogen budget and soil N dynamics after multiple applications of unlabeled or ^ Nitrogen-enriched dairy manure

cially if manure is surface-applied (Thompson et al., 1987). Conversely, denitrification losses of manure N Repeated N applications to field crops, either as inorganic fertilizers are increased by incorporation or injection (Comfort et or animal manures, can lead to N buildup in soils with potential longterm environmental hazards. The objective of this 3-yr field study al., 1988), and because organic matter in manure serves was to monitor totaland mineral-N levels in soil after repeated as a substrate for denitrifier microorganisms, tend to be fertilizer or single or repeated dairy manure applications, and to comhigher than denitrification losses in fertilized soils pute an N balance for the soil-crop system. Unlabeled and 15N-enriched (Cates and Keeney, 1987). Immobilization of inorganic dairy manure were used. The experiment was conducted on a Plano N in manure, plus the greater volatilization and denitrificorn silt loam continuously cropped to corn (Zea mays L.) Manure cation losses, cause inorganic N in manure to be less increased totaland NO3–N levels in soil, especially in the 0to 30-cm plant-available than equal rates of inorganic fertilizer depth and in plots receiving frequent and recent manure applications. Manure increased NO3–N in the 0to 30-cm soil layer more than (Paul and Beauchamp, 1993). Because of its lower N fertilizer N, whereas the opposite was true in the 30to 60and 60availability, greater amounts of manure than fertilizer to 90-cm layers. There was a clear NO3–N buildup with repeated N are applied to crops. This can result in a steady accumanure treatments. Unlabeled N measurements were not accurate mulation of soil N. Long-term soil N accumulation on enough to track trends in soil total N levels, hampering the calculation dairy farms poses a serious environmental risk (Bouldin of an N balance. 15Nitrogen-labeled manure allowed for direct meaet al., 1984). Heavy and/or repeated manure applications surement and provided more accurate estimates of N recovery in soils and crops. During the 3-yr study period, an average of 18% of applied can lead to NO3–N buildup in soil and losses through manure 15N was recovered in corn silage and 46% remained in the leaching (Adriano et al., 1971; Mathers and Stewart, soil. Unaccounted-for 15N (36%) was assumed to be lost mainly by NH3 1974; Smith et al., 1980; Cooper et al., 1984). Dairy farms volatilization and denitrification. Most (82%) of the 15N remaining in in the Midwest are considered significant contributors of soil was present in the top 30 cm, irrespective of frequency of manure N to the hypoxic zone in the Gulf of Mexico (Burkart application. Although costly and time-consuming, the use of 15Nand James, 1999). labeled manure provided a much better approach to study the fate Excessive soil nutrient accumulation and losses to of manure N within the soil-crop system, compared with unlabeled manure. surface and ground water are pressing environmental challenges facing the dairy and other animal industries. As dairy herds expand to remain economically viable, I most agricultural soils, N is the most limiting a larger percentage of the available cropland is devoted nutrient, and it has to be supplied to cereal crops, to corn silage. The noted expansion of corn silage proparticularly in high productivity systems (Meisinger, duction (Battaglia, 1999; Shaver, 2000) is due to this 1984). Fertilizers, manure, and in some cases, legumes, crop’s ability to feed more cows (Bos taurus) than other are the principal N sources for crop production in mixed, forages per unit of cultivated area (Seglar, 1998), as well dairy-crop production systems. Whereas fertilizer N is as favorable economics (Klemme, 1998) to the farmer. readily soluble in soils and becomes immediately availHowever, the effects of shifting more land to corn silage able for crop uptake, it can also be highly susceptible on other system components, such as N use, buildup to leaching losses. Comfort et al. (1987) found that soil and loss remains to be determined. Since only a relainorganic N and downward movement were increased tively small amount of applied N is ultimately taken up to a greater extent by fertilizer than by manure N. On by the crop, we wanted to track the fate of the unused the other hand, only about half of manure N is inorganic, portion to see whether it was lost or remained in the soil. with the rest being present in organic forms. Organic N The objective of this study was to determine total and must be mineralized before it can be used by plants or inorganic soil N and the N balance of a continuous corn it becomes susceptible to losses. However, when fresh silage cropping system receiving two fertilizer or dairy manure or slurry contain appreciable amounts of urea manure N rates of different application frequency across or NH4, N can be easily lost via NH3 volatilization, espe3 yr. Unlabeled and 15N-enriched dairy manure were used, and the ability of each manure type to detect G.R. Muñoz and K.A. Kelling, Dep. of Soil Science, Univ. of Wiscontrends in soil N levels and account for applied N was sin, 1525 Observatory Dr., Madison, WI 53706; and J. Mark Powell, USDA-ARS Dairy Forage Research Ctr., 1925 Linden Dr. West, compared. The use of 15N-labeled manure was an essenMadison, WI 53706. Received 22 Feb. 2002. *Corresponding author tial part of the study because it allowed direct N tracking (grmunoz@uwalumni.com). in the cropping system, and provided more accurate measurements than unlabeled manure. Published in Soil Sci. Soc. Am. J. 67:817–825 (2003).

Potato responses to calcium application on several soil types

On low cation exchange capacity, sandy soils where soil test Ca is low, potato tuber (Solanum tuberosum L.) Ca levels may not be optimal for maximum yield or quality; therefore, this study evaluated the effect of several levels of applied Ca on potato yield and quality on four soil types in Wisconsin. Calcium was applied to a Plainfield loamy sand, a Keiner loamy sand, a Pence sandy loam, and an Antigo silt loam at five rates in 1984 (0, 84, 252, 420, and 588 kg Ca ha−1) and at six rates in 1985 (0, 56, 112, 168, 224, and 336 kg Ca ha−1) as a band of CaSO4 in the hill. In 1984, on the Plainfield soil, three rates of sidedress Ca(NO3)2 (0, 84, and 168 kg Ca ha−1) were factorially combined with the five CaSO4 treatments to evaluate the efficacy of Ca(NO3)2 as a concomitant Ca and N source. In general, total yield was not affected by CaSO4 additions; however, the addition of approximately 100 kg Ca ha−1 as Ca(NO3)2 increased total yield 3.6 Mg ha−1. On the low-CEC, low-Ca soils (Plainfield and Kelner), improved tuber grade and/ or US1A size grade were detected with the addition of up to approximately 300 kg Ca ha−1 as CaSO4. The percent of US1A tubers increased 5 to 10% and the yield of US1A prime size (170–370 g) tubers increased 3.4 to 8.4 Mg ha−1 above control values. These improvements were accompanied by increased periderm Ca concentrations, even though leaflet Ca concentrations were not affected by Ca applications. The use of 100 kg Ca ha−1 asCa(NO3)2 in combination with CaSO4 was more effective than CaSO4 alone. On higher soil test Ca soils (Pence and Antigo), responses were inconsistent and periderm Ca was generally not increased.ResumenEn condiciones de una baja capacidad de intercambio de cationes (CIC), suelos arenosos donde las pruebas o determinación de calcio en el suelo es baja, los niveles de calcio en los tubérculos de papa (Solanum tuberosum L.) pueden no ser óptimos para un máximo rendimiento o una buena calidad de los mismos. Por lo tanto, en este estudio se evaluó el efecto de la aplicación de varios niveles de Ca en el rendimiento y calidad de la papa en cuatro tipos de suelo, en Wisconsin. Se aplicó calcio a un suelo arenoso franco Plainfield, a un arenoso franco Keiner, un franco arenoso Pence, y a un limoso franco Antigo en cinco dosis diferentes en 1984 (0, 84, 252, 420, 7 588 kg Ca ha−1) y en seis dosis en 1985 (0, 56, 112, 168, 224, y 336 kg Ca ha−1) como CaSO4 en una banda en el camellón. En 1984, en el suelo Plainfield, tres dosis de Ca(NO3)2 (0, 84, y 168 kg Ca ha−1) aplicadas lateralmente, combinados factorialmente con las cinco dosis de CaSO4, para evaluar la eficacia de Ca(NO3)2 como fuente simultánea de Ca y N. En general, el rendimiento total no fue afectado por las adiciones de Ca SO4; sin embargo, la adición de aproximadamente 100 kg Ca ha−1 en forma de Ca(NO3)2 incrementó el rendimiento total en 3,6 Mg ha−1. En suelos de baja CIC, bajo contenido de Ca (Plainfield y Keiner) se detectaron mejoras en al grado general y en el grado de tamaño de tubérculos con clasificación US1A con la adición de 300 kg Ca ha−1 en forma de CaSO4. El porcentaje de tubérculos US1A se incrementó en 5 a 10% y el rendimiento de tubérculos de primer tamano US1A (170–370 g) aumentó 3,4 a 8,4 Mg ha−1 sobre los valores del testigo. Estas mejoras fueron acompañadas por un aumento en las concentraciones de Ca en el periderma, aún cuando las concentraciones de Ca en los foliolos no fueron afectadas por las aplicaciones de Ca. El uso de 100 kg Ca ha−1, como Ca(NO3)2, en combinación con CaSO4, fue más efectivo que el CaSO4 solo. En suelos con determinación más alta de Ca (Pence y Antigo), las respuestas fueron inconsistentes, y el Ca en el periderma no fue incrementado por lo general.

Relationship of calcium nutrition to internal brown spot of potato tubers and sub-apical necrosis of sprouts

Potato tubers from field plots of calcium experiments in 1983 and 1984 were examined for the presence of internal brown spot. Presence of sub-apical necrosis on sprouts was also determined after storage in both years. Peel calcium concentration of 1983 tubers ranged from 0.226% to 0.130%; the range in percentage of these tubers with internal brown spot after 7 months storage was from 5.0% to 42.5%. The incidence of internal brown spot as well as sub-apical necrosis of sprouts was negatively correlated with tuber peel calcium levels (r = −0.754 and r = −0.792, respectively). Peel calcium concentration of 1984 tubers ranged from 0.224% to 0.104%; as in 1983, tuber calcium concentration was negatively correlated with the incidence of internal brown spot and sub-apical necrosis. Sub-apical necrosis of sprouts was present on 86.3% of the 1984 tubers with internal brown spot, and 65.3% of tubers with sub-apical necrosis on sprouts showed internal brown spot symptoms. The presence of sub-apical necrosis on tuber sprouts may serve as an indirect indicator of low calcium concentration in tubers.

Influence of fertilizer management and soil fertility on tuber specific gravity: a review

Tuber specific gravity is a measure of potato internal quality and is used by the potato processing industry for assessing crop acceptability. Potato growers, therefore, have an interest in understanding how nutrient management practices influence specific gravity. This paper provides a review of research on fertilizer and soil fertility influences on specific gravity. Excessive application rates of nitrogen and potassium, along with excessive soil levels of either nutrient, may reduce tuber solids. Phosphorus applications may improve specific gravity when soil test phosphorus levels are low. Fertilizer materials with higher salt indices will decrease specific gravity more than fertilizer materials with lower salt indices.ResumenLa gravedad específica del tubérculo es un indicador de la calidad interna de la papa y es usado por la industria de procesamiento para evaluar la aceptabilidad del cultivo. Por lo tanto, los productores de papa tienen interes en comprender cómo es que las practicas de manejo influyen en la gravedad especifica. Este articulo proporciona una revision de la investigacion sobre la influencia que tienen el fertilizante y la fertilidad del suelo sobre la gravedad especifica. La aplicacion excesiva de nitrogeno y potasio junto con niveles excesivos en el suelo de cualquiera de los dos nutrientes puede reducir los solidos en el tuberculo. Las aplicaciones de fósforo pueden mejorar la gravedad específica cuando las pruebas de fósforo arrojan niveles bajos. Los fertilizantes con índices altos de sales reducirán la gravedad específica más que aquellos que tienen índices bajos de sales.

Field evaluation of nitrogen availability from fresh and composted manure.

Prediction of manure nitrogen availability to crops is key to ensuring adequate production while minimizing potential adverse environmental impacts. This field study estimated first-year and residual N availability from several manures subjected to various levels of processing, and evaluated the applicability of the pre-sidedress soil N test (PSNT) in fields receiving the different manures using corn (Zea mays L.) as the test crop. Plots received several rates of fresh (FP), dried (DP), or composted (CP) poultry (Gallus gallus domesticus) manure, composted cow (Bos taurus) (CC) manure, ammonium nitrate (AN), or no N. Crop yields and N uptake from plots where CC was applied were undistinguishable from controls in most years, whereas poultry manures significantly increased corn production. Average apparent first-year N availability, as measured by fertilizer equivalence, was 57, 53, 14, and 4% for FP, DP, CP, and CC respectively. Apparent second-year N availability, as measured by relative effectiveness, was 18, 19, 12, and 7% for FP, DP, CP, and CC; however, for CC both first- and second-year estimates of apparent N recovery (ANR) could statistically not be separated from the controls. Apparent nitrogen avail-ability was greater for less processed manures and for CP compared to CC, emphasizing that producers should know the source and level of compost stability when these materials are used as a primary nutrient source. The PSNT successfully (87% correct) identified sites with a critical value of 24 mg kg(-1) that were N sufficient across a variety of N amendments from those that would have benefitted from additional N input.

Foliar fertilization of soybeans (Glycine max L.)

Abstract The effects of foliar fertilizer applications to soybeans during seed‐filling were examined using a complete factorial design with four levels each of nitrogen (N), phosphorus plus potassium (P+K) and sulfur (S). Hodgson soybeans were planted in 76‐cm rows on a Piano silt loam (Typic Argiudoll) in 1976 and 1977. Four fertilizer spray applications were made at 7‐ to 10‐day intervals beginning at stage R4 2. The application of N generally increased yield, seed weight, and percent N in the grain both years of the experiment. Phosphorus, K, and S had little influence on the parameters measured. Leaf burn after each fertilizer application was significantly increased by most levels of fertilizer addition.

Performance of dicyandiamide in the north central states

Abstract The effectiveness of the nitrification inhibitors, nitrapyrin and dicyandiamine, in reducing nitrogen loss from soil and preventing reduction in crop yield was evaluated in field studies conducted over dozens of site years in Illinois, Iowa, Minnesota, and Wisconsin on corn, wheat, and a vegetable crop, potato. Both chemicals were effective in retarding the nitrification of ammoniacal fertilizers, including nitrogen from liquid animal manures, but this inhibitor did not always result in yield increases above that obtained with equivalent amounts of nitrogen applied without inhibitor. Greatest benefits for nitrification inhibitor use was obtained on coarse‐textured soils under conditions that were conducive to nitrate nitrogen loss when nitrogen was applied at rates not considered to be excessive.

SOIL WATER FLUCTUATIONS IN A LOAMY SAND UNDER IRRIGATED POTATO

Diagnostic indicators were developed to evaluate water storage, infiltration, drainage, and uptake distribution patterns over a potato (Solanum tuberosum L.) hill to improve efficiency in drip and sprinkler irrigation. Soil water content time series were measured in the hills and in the furrow between hills using time domain reflectometry. The drainage indicator was significantly (P = 0.05) higher under sprinkler than drip beneath the furrow and at the toe location. Storage was low at the center under sprinkler irrigation (0.05 m3 m−3) where irrigation water did not infiltrate. Water storage was low at the shoulder location under both irrigation systems (significantly greater for sprinkler than drip) where high uptake rates were indicated. A diurnal/sinusoidal model of water uptake was fitted to a composite of the daily cycle of low-amplitude fluctuations with acceptable results (R2 = 0.39-0.72) for both systems at the shoulder and toe locations and at the center under drip. Uptake was virtually undetectable (R2 = 0.12-0.18) at the base and furrow locations. Deviations from the sinusoidal model were better accounted for by a polynomial model (R2 = 0.29-0.83) and seemed to indicate irrigation-induced flow and nonsinusoidal uptake. Electronic noise also contributed to the variability. The indicator of peak uptake time shifted from about 3 p.m. to 8 p.m., and uptake decreased as the depth from the top of the hill increased. Management practices targeted at wetting the hill center under the sprinkler would likely improve water use efficiency under these conditions.

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.