Biomass production of a sub-tropical grass under different photovoltaic installations using different grazing strategies

Abstract

CONTEXTWith increasing population growth and land-use competition, pasture production under photovoltaic installations offers an alternative paradigm for crop-livestock integration. The levels of pasture biomass production and potential for livestock grazing under photovoltaic installations depend considerably on the mode of the photovoltaic system. OBJECTIVEThis study aimed to model pasture production for sub-tropical grass under different photovoltaic installations and assess the effects of different grazing methods on sub-tropical pasture productivity in Australia. METHODSPasture biomass production under a fixed-tilt array, single-axis tracking array, and dual-axis tracking array were measured for the calibration and validation of Agricultural Production Systems sIMulator (APSIM) to simulate four different grazing strategies: (1) without grazing; (2) 21 days grazing interval; (3) 45 days grazing interval; and (4) continuous stocking. RESULTS AND CONCLUSIONSThe APSIM model showed satisfactory performance in simulating sub-tropical pasture production under different photovoltaic installations, with the best correspondence under the fixed-tilt array (observed value 6073 kg ha−1 and simulated value 6292 kg ha−1). As compared to full sun condition, biomass production was found to be 15.82, 13.53, and 8.03% higher with the fixed-tilt, single-axis tracking, and dual-axis tracking array, respectively. The model was then used in scenario analysis to evaluate pasture biomass production under different grazing strategies. Simulation results depict the grazing effect on pastures under the photovoltaic systems. Without grazing, maximum biomass production occurred under the fixed-tilt array (7798 kg ha−1) compared to under the single-axis tracking array (7671 kg ha−1), dual-axis tracking array (7186 kg ha−1), and full sun (6766 kg ha−1). In the case of 21 days and 45 days of grazing, the 25-year biomass production under the full sun was lower than all other systems. Compared to other treatments, the fixed titled array offers better performing pasture-grazing integration under a photovoltaic system. We found that models predicted that an increase in grazing pressure via continuous grazing had comparatively similar impacts on sub-tropical pasture biomass production irrespective of photovoltaic installations. Therefore, the potential exists to maximise land use efficiency where options are available to grow and graze pasture under photovoltaic installations. SIGNIFICANCEThis study confirms that the APSIM-Growth model, calibrated for Bambatsi Panic, can simulate pasture growth in different shading phenomena under the agrivoltaic system. Additionally, this simulation of the grazing systems is essential to identify crucial modelling and direct investigations that could expand knowledge of the procedures and relationships required for model development of pasture production under photovoltaic farms.