Hybrid Quality and Yield Differences for Corn Silage in Pennsylvania

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 sub-samples 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 (NIRS) 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 tons/acre 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. Research QuestionDifferences for forage quality traits have been reported in commercial corn hybrids. It is uncertain, however, how stable these differences are over diverse environments. Also, the relative importance of these differences compared to yield potential has not been well quantified. The objective of this study was to quantify quality differences of commercial hybrids in three environments in Pennsylvania and to compare the relative differences in quality to differences in yield. Literature SummarySeveral previous studies have reported digestibility differences among commercial hybrids of up to 5 to 6 percentage units and up to a 10 percentage unit range range in NDF. In the northeastern USA, large microclimatic and management differences between fields increase the potential for inconsistent hybrid performance or hybrid × location interactions. As a result, it is uncertain how consistent hybrid differences are for silage quality under the divere conditions encountered in this region. Study DescriptionNine widely grown commercial corn hybrids were evaluated for 2 yr at Rock Springs, PA, and 1 yr at Landisville, PA. Both locations had deep well-drained Hagerstown silt loam soils. Growing season rainfall ranged from 2.9 in. above normal at Rock Springs in 1990 to 2.8 in. below normal at Rock Springs in 1991. Each trial included all nine commercial hybrids (Table 1). Plant populations were 28 000 plants/acre and soil fertility amendments were managed according to Penn State soil tests. Nitrogen applications totaled 180 lb/acre, including credits from previous crops, All hybrids were harvested on the same day. Whole-plant and stover yield and forage quality were measured for each hybrid. Quality measurements included whole plant CP, NDF, TDN (based on ADF), and IVDMD and stover CP, NDF, and IVDMD. Applied QuestionsDo hybrid differences exist for forage quality when evaluated over diverse environments? Our study showed that consistent hybrid differences could be detected for whole plant yield, IVDMD, CP, and percentage ears. At individual locations, differences among the hybrids for some forage quality traits were substantial. For example, at Rock Springs in 1990, the range among hybrids for IVDMD was 4.1 percentage units. When averaged over locations, the range among hybrids in forage quality declined. As shown in Table 1, averaged over three environments, the range in IVDMD among hybrids was 2.7 percentage units. Corresponding differences in CP among the hybrids were 0.5 percentage units. Hybrid differences in stover IVDMD and NDF were inconsistent over locations. No differences among hybrids for TDN were detected. How do quality differences compare with differences in yield? Hybrid differences for yield averaged over the three environments varied up to 2.6 tons/acre. On a percentage basis, this represents an 11.5% range in yield performance. This compares with a 4.2% range for IVDMD, a 5.3% range for NDF, and a 6.6% range for CP. Consequently, the range in yield performance among the hybrids on a relative basis was approximately two to three times greater than differences in quality performance. The range in IVDMD among hybrids was largest in the highest yielding environment, suggesting that hybrid differences may be greatest in environments with the least stress. RecommendationsBased on these results, it appears that screening of new hybrids for quality differences should be considered, since hybrids with consistently lower whole plant and stover IVDMD exist that could be identified prior to marketing for silage purposes. For screening purposes, IVDMD appears to discriminate between hybrids better than measures based on fiber (NDF or TDN calculated from ADF). Table 1Average silage yield (35% DM) and quality of whole plant corn and corn stover for nine hybrids grown in three environments in Pennsylvania during 1990 and 1991. Whole-plantStoverBrandHybridYieldDM†IVDMDTDNNDFCPIVDMDNDFCPtons/acre--------------------------------- % of DM ---------------------------------CargillSX26918.544.065.771.343.17.854.773.55.2Cargill787719.242.866.271.842.77.454.872.65.1Cargill802720.439.665.670.943.37.555.470.65.4Doebler's75X19.139.766.271.242.17.354.772.65.2Doebler's84XP20.640.864.770.843.97.654.972.15.4Doebler's86X-A19.540.264.470.644.27.353.273.35.0Pioneer324121.040.265.271.642.87.853.170.55.4Pioneer334319.640.265.770.844.47.455.468.95.7Pioneer337918.544.365.371.242.67.354.272.05.7Mean19.641.365.471.143.27.554.571.85.3†DM = dry matter concentration, IVDMD = in vitro dry matter disappearance, CP = crude protein, TDN = total digestible nutrients, NDF = neutral detergent fiber.