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Amino acids and amino sugars comprise the bulk of soil N, so information on their chemical forms and cycling patterns should enable better understanding of soil N cycling. In this study of soil samples that had received animal manure, we evaluated the capabilities of a recently developed analysis for soil amino compounds (19 amino acids, two amino sugars) that consists of methanesulfonic acid extraction, anion chromatography, and pulsed amperometry detection. Soil samples were taken from a 28-d laboratory incubation of nine soils from six soil orders in six U.S. states that were amended with dairy manure slurry at a rate to simulate 300 kg N [ha.sup.-1]. Manuring resulted in enrichment of the soils by nearly all measured amino compounds but to varying degrees. These enriched levels were relatively stable against mineralization during the short-term incubation, with most compounds having decreased modestly in concentration (mean 11%) by the end of the incubation, in contrast to slight increases (mean 3%) for three compounds that are associated with microbial activity and were not overly abundant in the manure: ornithine, glucosamine, and galactosamine. Several measurements of the extracted amino compounds varied significantly among the nine soils. Our results illustrated some shortcomings of this analytical approach, including instability of small peaks and the need for a second extraction mode to maximize extraction of certain amino compounds. We identified 41 to 43% of the total soil N as amino compounds for all soils and treatments, which is comparable to results reported previously for the conventional analysis involving HCl extraction and cation chromatography. Compared with conventional analysis, this approach might more efficiently extract basic amino acids and less efficiently extract acidic amino acids. Overall we found this approach to be a useful analysis.

Manure and mineral fertilizer P sources vary in their contributions to soil P pools. We conducted incubation experiments to (i) assess temporal changes in soil P concentration for 84 d following application of K[H.sub.2]P[O.sub.4] or manure (beef, dairy, poultry, or swine), and (ii) to evaluate interactive effects of P rate, P source, and background P level on soil P pools 90 d after P application. Changes in soil P over time were evaluated following the amendment of a coarse-loamy, mixed, frigid Typic Haplorthod soil (pH 5.8) at a rate of 100 mg total P [kg.sup.-1] Water soluble P (WSP), 0.01 M Ca[Cl.sub.2]-extractable P (Ca[Cl.sub.2]-P), and modified Morgan P (MMP) declined to

Accurate prediction of Phytophthora infestans outbreak in a cropping season is crucial for the effective management of late blight on potato. The SIMBLIGHT1, SIMPHYT1 and modified SIMPHYT1 models were assessed for predicting late blight outbreaks relative to NOBLIGHT model by using climatic and crop data from field experiments at Presque Isle, ME, from 2004 to 2009. The dynamics of late blight infection pressures were computed by SIMPHYT3 model to assess the conduciveness of environmental conditions for late blight infection and potential for disease development. Infection pressure indicated conditions were moderately conducive for late blight development but varied across years. The SIMPHYT1 model recommended fungicide applications to commence on 11 July, 21 July, 8 July, 10 July, 7 July and 7 July for 2004, 2005, 2006, 2007, 2008 and 2009, respectively. The modified SIMPHYT1 model (US-version) recommended similar fungicide application dates for the same years with the exception of 2007. Model simulations of disease outbreak differed from actual recorded observations in untreated plots by 24–65 days. Simulation of SIMBLIGHT1 based on high and low soil moisture conditions in the field resulted in vast differences in dates of first fungicide application. Validation of the models (differences in the number of days between recommendation of fungicide treatment and late blight outbreak) indicated a better goodness of fit for the models (intervals of 6–20 days from the start of fungicide application to first disease outbreak). The NOBLIGHT model was accurate in forecasting the timing of first fungicide applications for late blight control. Significant improvements in late blight predictions could result if these models were modified to account for external sources of inoculum, by combining weather-based forecasts with spore traps, disease detection methods or complimentary systems. [ABSTRACT FROM AUTHOR]

Supplemental irrigation can be a viable means of increasing lowbush blueberry (Vaccinium angustifolium) crop yields in humid environments. To best utilize this management technique, Maine growers require accurate knowledge of regional crop water demands. Meteorological data and weighing lysimeters were used to determine Penman-Montieth grass reference evapotranspiration (ETo) rates and actual evapotranspiration rates of the lowbush blueberry at five irrigated and two nonirrigated fields of varying distance from the Maine coast. Mean daily values of air temperature, relative humidity range, and solar flux were all found to increase with increasing distance from the coast. The frequency of growing season fog hours increased from 3.7% of all hours at a distance of 22.5 km from the coast, to 11.1% of all hours at a distance of 0.8 km from the coast. Water equivalent inputs from fog per growing season at these two sites averaged 7.2 cm and 18.3 cm, respectively. These geographic climatic differences were reflected in the calculated evapotranspirationo rates, which also generally increased with distance from the coast. Four-year mean weekly ETo rates for July, the month of greatest potential water demand, were 2.76 cm/week, 3.21 cm/week, 3.52 cm/week, and 4.23 cm/week for sites located 0.8 km, 6.4 km, 22.5 km, and 48 km, respectively, from the coast. Actual ET rates for both crop and prune rotations followed a similar pattern of increasing magnitude with distance from the coast. For July, mean crop and prune year pooled weekly ET rates at 0.8 km, 6.4 km, and 22.5 km from the coast were: 1.69 cm/week (0.85), 2.28 cm/week (0.73), and 2.40 cm/week (0.83), respectively. Standard condition crop coefficient (Kc) values for both rotations during the months of May through September were calculated to be 0.68 for sites 6.4 and 22.5 km from the coast. Thus, it would appear that the same Kc value can be used universally within the typical growing range of the Maine lowbush blueberry. These findings should substantially contribute to improved water use efficiency for the irrigated lowbush blueberry in Maine. [ABSTRACT FROM AUTHOR]

Confirms the effectiveness of using growing degree days to predict nitrogen release from livestock manures and other soil amendments. Mineralization of organic nitrogen in manure; Nitrate accumulation in manure amended soil.