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Perennial-based buffer strips have been promoted with the potential to improve ecosystem services from riparian areas while producing biomass as livestock feed or as a bioenergy feedstock. Both biomass production and nutrient removal of buffer strips are substantially influenced by the vegetation types for the multipurpose perennial buffers. In this 2016–2019 study in Western Illinois, two perennial cropping systems, including forage crops composed of cool-season grass mixtures (forage system) and bioenergy crops made up of warm-season grass mixtures (bioenergy system), were used to establish buffer strips for assessing biomass production, feedstock quality, nutrient removals, and buffer longevity. Treatments for this study reflecting agronomic practices included 1) two harvests occurring in summer (at anthesis) and fall (after complete senescence) and 2) one harvest in fall for forage system (2- vs. 1-cut forage), and 3) one fall harvest for bioenergy system (1-cut bioenergy). Successively harvesting without any fertilizer input resulted in a yield decline in forage biomass over three years by approximately 30 % (6.3 to 4.4 DM Mg ha-1 with the rate of 1.0 Mg ha-1 yr-1) in the 2-cut forage and by 35 % (4.9 to 3.2 DM Mg ha-1 with the rate of 0.9 Mg ha-1 yr-1) in the 1-cut forage systems. The feed quality also decreased over the years by showing declined rates of 12.9 (crucial protein), 0.9 (calcium), 0.7 (copper), and 1.3 (zinc) g kg-1 DM yr-1. Empirical models predicted enteric CH4 emissions from cattle ranged from 225.7 to 242.6 g cow-1 d-1 based on the feed nutritive values. In contrast, bioenergy biomass yield increased by 27 % from 4.9 to 6.7 DM Mg ha-1 with consistent quality (cellulose ~ 397.9 g kg-1; hemicellulose ~ 299.4 g kg-1), corresponding to the increased total theoretical ethanol yield from 1.8×103 to 2.4×103 L ha-1 (~33 % increase). Annual nutrient removals of N, P, K, Ca, and Mg were significantly higher in the forage systems (e.g., 2-cut: 52.6~106.9 kg-N ha-1; 1-cut: 44.5~84.1 kg-N ha-1) than those in the bioenergy system (e.g., 25.9~34.4 kg-N ha-1); however, the removal rate declined rapidly over three years (e.g., ~49 % reduction) as the annual biomass yield declined in the forage systems. This on-farm field study demonstrated the potential of the perennial crop used as buffer strip options for biomass production and buffer sustainability at the edge of the field. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) emissions from agricultural soil are substantially influenced by nitrogen (N) and field management practices. While routinely soil chambers have been used to measure emissions from small plots, measuring field-scale emissions with micrometeorological methods has been limited. This study implemented a backward Lagrangian stochastic (bLS) technique to simultaneously and near-continuously measure N2O emissions from four adjacent fields of approximately 1 ha each. A scanning open-path Fourier-transform infrared spectrometer (OP-FTIR), edge-of-field gas sampling and measurement, locally measured turbulence, and bLS emissions modeling were integrated to measure N2O emissions from four adjacent fields of maize production using different management in 2015. The maize N management treatments consisted of 220 kg NH3-N ha−1 applied either as one application in the fall after harvest or spring before planting or split between fall after harvest and spring before planting. The field preparation treatments evaluated were no-till (NT) and chisel plow (ChP). This study showed that the OP-FTIR plus bLS method had a minimum detection limit (MDL) of ±1.2 µg m−2 s−1 (3σ) for multi-source flux measurements. The average N2O emission of the four treatments ranged from 0.1 to 2.3 µg m−2 s−1 over the study period of 01 May to 11 June after the spring fertilizer application. The management of the full-N rate applied in the fall led to higher N2O emissions than the split-N rates applied in the fall and spring. Based on the same N application, the ChP practice tended to increase N2O emissions compared with NT. Advection of N2O from adjacent fields influenced the estimated emissions; uncertainty (1σ) in emissions was 0.5 ± 0.3 µg m−2 s−1 if the field of interest received a clean measured upwind background air, but increased to 1.1 ± 0.5 µg m−2 s−1 if all upwind sources were advecting N2O over the field of interest. Moreover, higher short-period emission rates (e.g., half-hour) were observed in this study by a factor of 1.5~7 than other micrometeorological studies measuring N2O-N loss from the N-fertilized cereal cropping system. This increment was attributed to the increase in N fertilizer input and soil temperature during the measurement. We concluded that this method could make near-continuous "simultaneous" flux comparisons between treatments, but further studies are needed to address the discrepancies in the presented values with other comparable N2O flux studies. [ABSTRACT FROM AUTHOR]