CO2 Emissions and Maize Biomass Production Using Digestate Liquid Fraction in Two Soil Texture Types

Abstract

Abstract. The aim of this work was to evaluate the effects of soil texture and primary tillage type on soil CO2 emission and maize biomass production after digestate liquid fraction (DLF) spreading. The study was conducted in 2014 in two open fields at Terrasa Padovana (farm 1) and Bovolenta (farm 2) in the Veneto Region of Italy. Soil CO2 emission after digestate spreading was evaluated by comparing the effect of soil texture (sandy loam vs. clay loam) at farm 1 and the effect of long-term primary tillage management (>10 years) (ripping vs. plowing) in clay loam soil at farm 2. Unamended soil was considered the control at both farms. DLF was supplied before maize ( L.) sowing at a dose equal to 170 kg total nitrogen ha-1 using a splash-plate technique. DLF spreading determined a CO2 emission peak 1 h after spreading at both farms, with median emission values of 8.93 and 4.35 g m-2 h-1, respectively, from the sandy loam and clay loam soils at farm 1. At farm 2, primary tillage type did not exert a significant effect on CO2 emission peak, with a median value of 5.85 g m-2 h-1. About three days after DLF distribution, soil CO2 fluxes were less than 1 g m-2 h-1. The first soil harrowing and the first rainfall event after spreading determined significantly higher CO2 emissions from amended plots than from unamended plots for a few hours. At farm 1, soil CO2 emission during the maize growing season was significantly higher in the amended plots (+1.7 times) than in the unamended plots, which showed a median emission value of 0.29 g m-2 h-1; soil texture and tillage exerted no significant influence. Maize yield at dough stage was not significantly influenced by DLF at farm 1, with 22.7 ±1.6 Mg ha-1 and 18.7 ±2.8 Mg ha-1 in the clay loam and sandy loam soils, respectively. At farm 2, the distribution of DLF increased maize biomass production by +17% with respect to the unamended treatment that produced 18.0 ±2.4 Mg ha-1. Although the results reported in this article concern data from only one year, and further long-term experiments are needed to confirm our findings, they indicate that CO2 emissions after digestate distribution are lower in a clay loam soil than in a sandy loam soil and are not affected by primary tillage type. Keywords: Clay loam soil, Digestate splash-plate spreading, Plowing, Ripping, Sandy loam soil.