Use of a presidedress soil NO3- test (PSNT) for corn (Zea mays L.) could help to minimize uncertainties associated with managing N contributions from manure and legume crop residues. Understanding the performance and impact of this test under a wide range of conditions is necessary to target its use. A proposed quicktest method could improve the utilization of this test. This study was established to evaluate: (i) soil NO3- levels at sidedressing and the impact of the PSNT on fertilizer use under a range of field history classifications and (ii) the accuracy of the quicktest performed by persons with minimal laboratory experience. Quicktest kits were developed and distributed to extension agents and crop consultants. These cooperators offered free soil testing to farmers and collected field history information on each sample they analyzed (2725 samples). A subset (610 samples) was sent to a soil testing laboratory to compare quicktest and standard laboratory results. Quicktest accuracy was less than the laboratory method but adequate to ensure recommendations within 25 lb of the laboratory recommendation in 82% of the cases. Soil NO3- levels in manured fields were 3.3 ppm higher than nonmanured fields. Soil NO3- levels from fields following alfalfa (Medicago sativa L.) without a manure history were not different than fields with no legume and no manure, indicating the PSNT did not account for the increased N availability from alfalfa residues. Based on this research, the PSNT is effective to reduce unnecessary N applications to corn, particularly where high soil NO3- levels result from manure applications.
Differences among corn (Zea mays L.) hybrids for forage quality traits have been reported, but the stability of forage quality differences over diverse environments is not well documented. To evaluate hybrid stability for yield and forage quality, nine commercial hybrids were evaluated at two locations in Pennsylvania in 1990 and one location in 1991. All hybrids were harvested on the same day at the 2/3 milk line to black layer stage, depending on the hybrid. Whole plant and stover subsamples were collected from each plot, chopped, dried and ground for analysis. Forage analysis for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and in vitro dry matter disappearance (IVDMD) was performed using near infrared reflectance spectroscopy on both whole plant and stover samples. Total digestible nutrients (TDN) was calculated based on the ADF concentration. Environmental effects were significant for yield and all quality traits. Hybrid effects were significant for all traits except TDN, ADF and NDF. The range among hybrids for whole plant IVDMD at individual locations was as high as 4.1 percentage units, but averaged over the three environments, the range among hybrids was 2.7 percentage units. Silage yield differences among hybrids, which ranged up to 2.6 T/A or 11.5 % of the mean, were larger on a percentage basis than any of the quality differences. The results of this study indicate that both yield and forage quality differences exist among commercial hybrids and that producers should consider both yield and quality attributes in selecting a hybrid for silage production.
The western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) has become a serious pest of continuous corn (Zea mays L.) in the northeast U.S. Several recommended crop production practices in this area such as early planting, sidedressing N applications, and no-tillage often contribute to slow early season growth, which could affect the potential for damage from the WCR. The objective of this study was to determine if these practices affected root damage ratings or yield reductions associated with the WCR. Field experiments were conducted in 1991, 1992, and 1993 on well-drained Hagerstown silt loam soils (fine, mixed, mesic typic Hapludalfs). Treatments in each study were factorial combinations of two tillage treatments (none and chisel/disk), three timings of nitrogen fertilizer application (at planting, sidedressed, or split), two planting dates (early and late May) and two insecticide treatments ( none and 1.12 kg ha-1 chlorpyrifos). Each treatment was replicated four times. Lodging, root damage ratings, root dry matter estimates and grain and silage yields were measured for each treatment. Root damage ratings were not affected by the planting date, N timing or the tillage system. Insecticide had a large and consistent effect on reducing root damage from the WCR. Root size estimates indicated that late planting reduced root size but did not affect root damage. These results indicate that reduced tillage, N sidedressing and early planting can be included in an IPM program with no risk of increasing the potential for root damage from the WCR.
Corn grain yield, forage yield, grain protein and forage protein data from twenty five N response experiments conducted in Pennsylvania were analyzed to determine the effect of harvest method and a price adjustment based on grain and forage protein content on the EON rate. The value of the protein in this study was assumed to be that of substituting soybean meal in the ration for growing beef cattle or dairy cattle. There was no difference in the EON for corn harvested for grain compared to corn harvested for forage when the protein content was not considered. When price adjustments were made for the protein content of the grain and forage, the EON rates increased 10 kg/ha for grain and 22 kg/ha for forage. With the protein price adjustments, the EON was 14 kg/ha higher for forage than grain. These results support the recommendation for higher N rates for corn harvested for forage, where the protein value of the forage is considered, compared to corn harvested for grain.