William J. Cox

Spatial and temporal processes affecting nitrogen availability at the landscape scale

Nitrogen dynamics in soils are affected by spatial and temporal processes. Drainage class is generally regarded to be the most significant source of variability for N in temperate humid climates. A 5-year study was conducted including four rates of N fertilizer and three drainage classes within a 15 ha maize (Zea mays L.) field. Variance component analysis showed that N response was minimally affected by drainage class, but showed strong yearly variations, apparently related to early-season precipitation. Annual field-averaged economic optimum N rates had a range of 65 kg ha ˇ1 with lower rates being associated with years with low early-season precipitation. A calibrated LEACHMN model and site-specific weather data were used to evaluate the effects of early-season weather conditions on N rate and availability. During wet years, soil N availability was reduced by approximately 35‐50 kg ha ˇ1 compared to dry years, largely independent of drainage class. For well-drained soils, most losses were attributed to leaching (especially in years with wet early-season), while poorly drained soils mainly experienced denitrification. It is concluded that limited benefits may be gained from spatially variable N applications within fields based on drainage class or soil type, but considerable economic and environmental gains are possible from yearly adjustment of supplemental N rates based on model simulations of N dynamics using information on early-season weather conditions. # 2001 Elsevier Science B.V. All rights reserved.

Growth development and yield of maize under three tillage systems in the northeastern U.S.A.

Abstract Cool spring temperatures are a major constraint to maize ( Zea mays L.) production in northern regions of the U.S.A., and a no-till (NT) system intensifies the problem because residue on the surface further decreases soil temperature. Ridge tillage (RT), because of the configuration of the ridge and the removal of most of the residue from the seed zone during the planting operation, may alleviate this problem. Field experiments were established in New York on a drained and undrained silt loam soil (fine-loamy, mixed, nonacid, mesic Aeric Haplaquept) to examine the influence of a fall-plowed, or conventional tillage, system (CT), NT, and RT on soil temperature growing degree days (GDD) and subsequent growth, development, and yield of maize in continuous production. Soil GDD averaged about 35–40 GDD less under NT during the first 35 days after emergence, which resulted in a consistent three-day delay in silking and a lower maximum leaf area index (LAI) and crop growth rate (CGR). Under drained conditions, grain yields under NT averaged 10% lower than CT (8.68 and 9.60 Mg ha −1 , respectively). In two of the three years, however, higher CGR under NT duringv the grain-filling period resulted in the same total phytomass and grain yields as under CT. Soil GDD averaged about 10 GDD more under RT than under CT and the development of maize under RT and CT was essentially the same. Nevertheless, under drained conditions, the growth of maize under RT was slightly slower than under CT and grain yields (9.05 Mg ha −1 ) averaged 5% lower. In the undrained experiment, where some flooding occurred in two of the three years, grain yields were significantly higher under RT than under CT and NT (7.92, 7.09, and 7.19 Mg ha −1 , respectively). In 1988, when a two-day flooding period occured shortly after emergence, the configuration of the ridge reduced the duration of surface flooding from two days to one day, which resulted in increased plant survival, faster growth and development, and higher grain yields (7.36, 5.79, and 5.60 under RT, CT, and NT, respectively). In conclusion, RT appears to be a well adapted conservation tillage system for continuous maize production in northern regions, especially on soils that flood periodically.

Spatial Analysis of Maize Response to Nitrogen Fertilizer in Central New York

An increasing number of farmers are considering the use of site-specific nitrogen (N) applications to maize (Zea mays L.) as a way of maximizing yield potential while minimizing fertilizer cost. The objectives of this 3-years experiment were to evaluate the spatial structure of yield response to N fertilizer and investigate the potential for site-specific N management under maize production in New York. Four experimental N rates (50, 110, 160, or 220 kg ha∧1), two tillage systems (chisel till and zone-till) and two crop rotations (maize•maize and maize•soybean (Glycine max L.)) were superimposed over a 12 ha field in central New York State with a complex of Honeoye-Lima, Kendaia, and Lima soils ranging from moderately well to poorly drained soils. Pre-sidedress soil nitrate tests (PSNT) showed significant spatial structure but did not conform to that for crop N response, indicating that N fertilizer recommendations based on PSNT results cannot be simply applied in a site-specific management approach. Optimal N rate varied from 110 kg ha ∧1 for the dry years 1999 and 2000 to 220 kg ha∧1 for 1998, with a warm wet spring. Tillage treatments were generally comparable in N response. Spatial yield response analysis showed limited field-scale regionalization of both yield and profit response to N, suggesting that site-specific application of nitrogen is impractical. The greatest source of variability in N requirements was observed with the annual effects of weather, and presents a greater potential for precise N application than site-specific application. Annual variations in optimum N rate were not related to annual yield differences and yield potential itself does not appear to be a good predictor of N needs.

Soil Test, Aerial Image and Yield Data as Inputs for Site-specific Fertility and Hybrid Management Under Maize

Several potential sources of information exist to support precision management of crop inputs. This study evaluated soil test data, bare-soil remote sensing imagery and yield monitor information for their potential contributions to precision management of maize (Zea mays L.). Data were collected from five farmer-managed fields in Central New York in 1999, 2000, and 2001. Geostatistical techniques were used to analyze the spatial structure of soil fertility (pH, P, K, NO3 and organic matter content) and yield variables (yield, hybrid response and N fertilization response), while remote sensing imagery was processed using principal component analysis. Geographic information system (GIS) spatial data processing and correlation analyses were used to evaluate relationships in the data. Organic matter content, pH, P, and K were highly consistent over time and showed high to moderate levels of spatial autocorrelation, suggesting that grid soil sampling at 2.5–5.5 ha scale may be used as a basis for defining fertility management zones. Soil nitrate levels were strongly influenced by seasonal weather conditions and showed low potential for site-specific N management. Aerial image data were correlated to soil organic matter content and in some cases to yield, mainly through the effect of drainage patterns. Aerial image data were not well correlated with soil fertility indicators, and therefore were not useful for defining fertility management zones. Yield response to hybrid selection and nitrogen fertilization rates were highly variable among years, and showed little justification for site-specific management. In conclusion, we recommend grid-based management of lime, P, and K, but no justification existed within our limited study area for site-specific N or hybrid management.

Milk Production in High Producing Dairy Cows as Influenced by Corn Silage Quality

Greater milk production is the promised outcome for selecting corn hybrids with various traits that impact forage quality. Our objective was to select a set of hybrids most likely to exhibit differences in forage quality and evaluate milk production of cows fed a high forage diet. Four hybrids were selected for the feeding trial: a leafy hybrid (Mycogen TMF 100; Mycogen Seeds, Indianapolis, IN), a brown midrib (BMR) hybrid (Mycogen BMR F407), and two conventional hybrids varying in fiber digestibility (Pioneer 36B08 [Conventional 1 {CONV1}] and Pioneer 35P12 [Conventional 2 {CONV2}]; Pioneer Hybrid International, Inc., Des Moines, IA). Diets were formulated to provide 1.0% BW as forage NDF (approximately 32% NDF) and were balanced to meet or exceed NRC requirements. Fifty-six cows were fed for 56 d. The DMI of cows fed the BMR and the leafy hybrid total mixed rations (TMR) were greater than those of cows fed the other hybrids. Differences in milk production reflected the differences in intake. Cows fed the BMR (41.7 kg/d) and leafy hybrid (42.1 kg/d) TMR were not different from each other in milk production, but had greater (P≤0.05) milk

Forage Quality Differences of Corn Hybrids as Influenced by Ensiling

Our objective was to determine the impact of ensiling on forage quality of 54 corn hybrids (Zea mays L.). Four field replicates of each hybrid were planted at each of two locations in NY in 2003 (Groveland Station and Aurora, NY). There were differences among hybrids in pH (P < 0.01) at both sites. The pH of ensiled samples was positively correlated with silage DM (r = 0.82) and increased 0.016 pH units for each 1.0% increase in DM. Crude protein of ensiled samples was highly correlated (r = 0.95) with CP of fresh samples, but CP was 0.41% greater in the ensiled samples. Sugar of fresh samples averaged 9.9% while that of corresponding ensiled samples averaged 3.6%. Ranking of hybrids for sugar changed from fresh to ensiled, but was not consistent between sites. There were hybrid × ensiling/fresh interactions for NDF and IVTD at one site; this interaction was not significant at either site for fiber digestibility (NDFD). There was a significant correlation between fresh and ensiled sample NDFD (r = 0.74, P < 0.01). These data suggest little difference between fresh or ensiled hybrid rankings for NDFD, which implies that differences among hybrids in NDFD could be selected by using fresh samples. Inconsistencies for hybrid × ensiling/fresh interactions indicated that more research is needed to fully assess the relative benefits of ensiling prior to quality comparisons of corn hybrids.