Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a native perennial warm‐season grass with the potential to produce high yields of high quality forage. There is, however, little information on the response of eastern gamagrass to different harvest intervals and N rates. The objective of this research was to evaluate the forage yield, crude protein concentration, and total N removal by eastern gamagrass using different harvest intervals and N rates at two sites in northern Missouri. At Elsberry and Clifton Hill, MO, established stands of ‘PMK‐24’ eastern gamagrass were burned prior to green‐up each spring. Individual plots were randomly assigned either a 4‐ or 6‐wk harvest interval and five N rates (0, 50, 100, 150, or 200 lb N/acre) as ammonium nitrate and were evaluated in each harvest interval. In 1991 and 1992, total N and crude protein concentrations were determined on harvested forage and total N removal was estimated. Total forage yields were greater with the 6‐ than the 4‐wk harvest interval at Elsberry all 3 yr, and in 1 of 3 yr at Clifton Hill. In 1991, total forage yields did not increase with N rate with either harvest interval at Elsberry, nor the 6‐wk harvest interval at Clifton Hill. In 1992 and 1993, total forage yields increased linearly with N rate at Clifton Hill, and curvilinearly with N rate at Elsberry. Forage crude protein concentrations were consistently greater with the 4‐ than the 6wk harvest interval at both sites in 1991 and 1992. In general, forage crude protein concentrations increased linearly with N rate with both harvest intervals. In 1991, up to 200 lb N/acre was removed with the harvested forage at both sites. Total N removal increased linearly with N rate with both harvest intervals in 1991 and 1992 at Clifton Hill, but total N removal was variable at Elsberry. For grazing, a 4‐wk harvest interval will provide animals with higher protein forage. For hay production, a 6‐wk harvest interval may provide greater forage yields with fewer harvests. Research Question Eastern gamagrass is a native perennial warm‐season grass with the potential to produce high yields of high quality forage with multiple harvests during the growing season. Warm‐season grass forage yield and crude protein concentration can be increased by N fertilization. With multiple forage harvests, greater N rates may be needed to maintain high forage yields and crude protein concentrations. There is, however, little information on eastern gamagrass forage yield, protein concentration, or N removal under different harvest intervals and N fertilization rates. The objective of this research was to determine appropriate harvest intervals and N rates for eastern gamagrass in northern Missouri. Literature Summary In southern Illinois, eastern gamagrass forage yields ranged from 6690 to 21 720 lb/acre, and in northwestern Oklahoma, forage yields ranged from 14 020 to 20 290 lb/acre with multiple harvests taken during the growing season. Crude protein content of eastern gamagrass is high for a warm‐season grass ranging fr...

Environmental variation, and the interaction of environment with management practices, can significantly affect perennial forage yields. The objective of this research was to evaluate the importance of environmental main effects and the interaction between environments, N rates, and harvests on eastern gamagrass [Tripsacum dactyloides (L.) L.] forage yields. Established eastern gamagrass stands were fertilized with 0, 168, or 336 kg N ha−1, and harvested three times during the growing season for three consecutive years at two locations in northern Missouri. Year and the year × location interaction were significant environmental sources of variation affecting forage yields. The year main effect had the larger variance component and accounted for 9% of the total variation in forage yields. The harvest main effect and year × harvest interaction had the largest variance components, and together accounted for more than 67% of the total variation in forage yields. Most of the variation between harvests resulted from differences in first‐harvest yields, taken at the reproductive growth stage, compared with regrowth harvest yields which were at vegetative growth stages. Variation in precipitation amounts between harvests significantly influenced regrowth harvest yields, causing a significant year × harvest interaction. Forage yield responses to N rates also varied between years, causing a significant year × N rate interaction. Location was not an important source of variation in eastern gamagrass forage yield in this study, nor was there a significant interaction between N rates and harvests. Resultsuggest that supplemental irrigation and longer rest periods between harvests may help improve forage yields and distribution.

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Core Ideas Sample handling had profound and disproportionate effects on PLFA biomarkers. Gram positive and actinobacteria were not significantly affected by storage. Gram negative and fungal biomarkers were dramatically affected by storage. PLFA ratios significantly changed as a result of sample handling and storage. Interpretation of PLFA profiles is highly sensitive to sample handling. ABSTRACT Phospholipid fatty acid (PLFA) analysis is an increasingly popular method for estimating microbial biomass and assessing microbial community structure in soils. In particular, there is a strong interest in the use of PLFA microbial group ratios as benchmarks for soil health assessment and interpretation. Due to the sensitivity of PLFA biomarkers, the recommended procedure for sample handling involves immediate analysis of fresh, field‐moist soil, immediate lyophilization with freezer storage, or storage at –80°C. This protocol may not be practical under all circumstances, yet the effects of handling and storage conditions, and the implications for interpretation of PLFA biomarkers, are not fully understood. The primary objective of this study was to evaluate the effects of multiple sample handling and storage conditions on quantification and interpretation of PLFA biomarkers. A suite of soil properties were measured on 17 prairie soil samples, including PLFA analysis. Multiple processing and handling procedures were evaluated by splitting the soil samples and comparing PLFA profiles from (i) fresh soil, (ii) soil stored air‐dry for 7 and 14 d, (iii) soil stored field‐moist at room temperature for 7 and 14 d, and (iv) soil oven‐dried for 24 h at 105°C. All handling and storage procedures resulted in significant losses of PLFA biomarkers relative to fresh, lyophilized samples and microbial groups were disproportionately affected, leading to significant shifts in biomarker ratios. Overall, this study highlights the sensitivity of PLFA biomarkers, the importance of proper sample handling for PLFA analysis, and the potential for error and misinterpretation of PLFA data.

Perennial grass silages are needed as alternatives to corn (Zea mays L.) silage on erosive cropland. Eastern gamagrass [Tripsacum dactyloides (L.) L.] may offer an alternative to corn for silage production, but it's fermentation characteristics and quality under different rates of N have not been evaluated. A 5‐yrold stand of ‘PMK‐24’ eastern gamagrass was treated in 1991 and 1992 with ammonium nitrate at 0, 100,and 200 lb N/acre and harvested for silage. Corn was grown adjacent to the eastern gamagrass stand in 1992 for comparison. First harvest eastern gamagrass forage was ensiled at the seed development stage in 1991 and inflorescence emergence stage in 1992, and regrowth forage at the vegetative stage both years. Eastern gamagrass silage pH was not influenced by stage of maturity or N rates, and averaged 0.4 to 0.8 pH units greater than corn silage. Concentrations of lactic and acetic acid in eastern gamagrass silage ranged from 1.1 to 3.0%, were not affected by N rates, and were greater than for corn silage. Eastern gamagrass silage had 2.6 to 4.2 percentage units greater crude protein (CP), 11.5 to 15.3 percentage units greater acid detergent fiber (ADF), 8.0 to 15.5 percentage units greater neutral detergent fiber (NDF), 1.8 to 6.1 percentage units greater lignin concentrations, and 10.9 to 21.3 percentage units lower in vitro dry matter digestibility (IVDMD) than corn silage. Eastern gamagrass harvested at inflorescence emergence or vegetative stages had 2.0 to 3.5 percentage units greater CP, 3.2 to 7.5 percentage units lower ADF, and 2.3 to 17.0 percentage units lower NDF concentrations than eastern gamagrass harvested at the seed development stage. Increased rates of N increased eastern gamagrass silage CP 1.6 to 3.0 percentage units, and tended to decrease ADF and NDF concentrations. If harvested at the vegetative or inflorescence emergence stage and proper moisture content, eastern gamagrass makes good quality silage, but of lower IVDMD than corn. Producers interested in using eastern gamagrass in place of corn for silage production on marginal and erosive cropland will have to weigh the potential benefits of reduced annual input costs and reduced soil erosion against reduced forage quality. Research Question Corn silage production can result in considerable soil erosion on marginal and sloping cropland. To create more sustainable silage production systems and help reduce soil erosion, high yielding, high quality perennial grass silages are needed as alternatives to corn for silage production on erosive cropland. Eastern gamagrass is a high quality, native perennial warm‐season grass with forage dry matter yields that compare favorably with corn silage. However, before eastern gamagrass can be recommended as an alternative to corn for silage production on erosive cropland, the fermentation characteristics and quality of eastern gamagrass silage must be evaluated under different N rates. The objective of this research was to evaluate the fermentation characteristics and quality of first cut and regrow...