Biochar and nitrogen application rates effect on phosphorus removal from a mixed grass sward irrigated with reclaimed wastewater

This 2-year (2017 and 2018) field study evaluated biochar and nitrogen application rates effect on herbage phosphorus (P) and nitrogen (N) removal from a mixed-grass sward of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] and Kentucky bluegrass (Poa pratensis L.) irrigated with treated wastewater. Treatments used in this study carried out at the Main Station Field Laboratory, Reno, NV were three biochar application rates (0, 8.9, and 17.8 Mg/ha), and three N rates (0, 80, and 120 kg N/ha) arranged in a 3 × 3 factorial in a randomized complete block design experiment with four replications of each treatment combination. Responses were considered different P < 0.05. There was a linear increased in soil volumetric water content as biochar rate increased from 0 to 17.9 Mg/ha. However, biochar application rate did not affect the quantity of biomass produced, forage tissue P and N concentrations, P and N removal or interact with the other experimental variables of N rate and year to influence the response variables. There was, however, an N rate effect (P < 0.05) on biomass production and it was greater for the 80 and 120 kg N rate (average = 8.3 Mg DM/ha) relative to the 0 kg N/ha rate (6.0 Mg DM/ha). Further, cumulative P removal for the 80 and 120 kg N rate (average = 48.9 kg/ha) was greater than the 0 kg N/ha rate (38.1 kg/ha), and cumulative N removal was in the order 120 kg N/ha (321.1 kg/ha) > 80 kg N/ha (267.4 kg/ha) > 0 kg N/ha (187.8 kg/ha). There was a trend for a biochar × N rate interaction on soil P concentration and it tended to be greater for the combinations 8.9 and 17.8 Mg/ha biochar rates and 80 and 120 kg N/ha rates compared to the unamended control. Even though our study did not reveal a definitive effect of biochar on the major response parameters (biomass, tissue P and N concentrations) evaluated, the trend for a biochar × N rate interaction on soil P concentration offers hope that biochar-amended soils coupled with appropriate N fertilization will be effective in P retention on agricultural landscapes irrigated with treated wastewater.

Fermentation characteristics and nutritive value of baled grass silages made from meadow fescue, tall fescue, or an orchardgrass cultivar exhibiting a unique nonflowering growth response

Throughout central Wisconsin, many soils are poorly drained, and perennial cool-season grasses are often planted as monocultures or in mixed stands with alfalfa because of the poor persistence of alfalfa under these growing conditions. Our objectives were to compare the fermentation characteristics and nutritive value of perennial cool-season grasses {meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), and endophyte-free tall fescue [Schedonorus phoenix (Scop.) Holub]} conserved as baled silages with or without particle-size reduction, and at 2 moisture concentrations. Twenty-four plots (0.23 ha) were arranged in a randomized complete block design with 6 plots/block. Within each of the 4 field blocks, one of the 6 plots was assigned randomly to each of the (3 × 2) factorial combinations of forage type and bale cutting engagement (cut or uncut). The baler cutting mechanism consisted of 15 cutting knives, thereby creating a theoretical length of cut of about 8.1 cm. Generally, sufficient forage was available to produce 2 bales/plot; therefore, one bale was packaged at relatively high moisture (58.3%), whereas the other bale was made at an ideal moisture (44.9%) for this silage preservation method. Theoretically, bale cutting can increase bale weights and densities by reducing particle size, thereby allowing inclusion of additional forage within the same-sized bale. In this experiment, bale-cutting within 1.2 × 1.2 m silage bales (n = 47) increased initial wet and dry bale weights by 4.1 and 4.7%, respectively, but had no practical effect on measures of nutritive value, either on a pre- or postensiled basis. Cutter engagement tended to increase total volatile fatty acids in silages, thereby resulting in a pH reduction of 0.07 pH units (5.54 vs. 5.61). A unique nonflowering growth response by the first-cutting orchardgrass forage resulted in yields of dry matter for orchardgrass (2,977 kg of dry matter/ha) that were only 52 to 53% of those observed for meadow (5,580 kg of dry matter/ha) or tall fescue (5,763 kg of dry matter/ha), which did not differ. Despite the unique vegetative nature of orchardgrass, concentrations of neutral detergent fiber, acid detergent fiber, and acid detergent lignin determined before ensiling exhibited limited variability across forages (60.9 to 62.7%, 35.2 to 36.4%, and 2.75 to 2.99%, respectively). However, a 30-h in vitro incubation determined that orchardgrass exhibited greater neutral detergent fiber digestibility (56.2%) compared with meadow (44.9%) or tall fescue (40.8%), which were also statistically distinct.