The Effect of Eco-Friendly/Sustainable Agricultural Practices (Legume Green Manure and Compost Soil Amendment) on a Tobacco Crop Grown Under Deficit Irrigation

A field experiment was conducted in 2018 at Marciano della Chiana (Arezzo, AR, Central Italy) with the main aim of investigating the effect of soil amendment with organic fraction municipal solid waste (OFMSW) compost and legume green manuring (Vicia villosa Roth, cv. villana) on a tobacco crop (dark fire-cured Kentucky type, cv. Foiano) grown under both full (100% of ETc) and deficit (70% of crop evapotranspiration, ETc) irrigation. The treatments are hereafter reported as GM (vetch green manuring) and NGM (no vetch green manuring), FI (full irrigation) and DI (deficit irrigation), and C (compost soil amendment) and NC (no compost soil amendment). The following parameters were calculated: (i) yield of the cured product (CLY, Mg ha-1) at a standard moisture content of 19%; (ii) irrigation water use efficiency (IWUE, kg of cured product m-3 seasonal irrigation volume), nitrogen (N) agronomic efficiency (NAE, kg of cured product kg-1 mineral N by synthetic fertilizers). Dry biomass accumulated in the stem and leaves (Mg ha-1) was also measured at 25, 57, 74, and 92 days after transplanting (DAT). The N recovery from the different plant parts (kg ha-1) was determined at 57 and 74 DAT. The C/N ratio, NO3-N (kg ha-1), the soil organic matter (SOM, %), and the soil contents of P2O5 and K2O (mg kg-1) were also analytically determined at 43, 74, and 116 DAT. Water retention measurements were carried out on soil samples at 116 DAT at 0-0.3 and 0.3-0.6 soil depths. Overall, there was a negative effect of both compost amendment and green manuring on yield. Green manuring and compost soil amendment improved soil chemical characteristics (i.e., SOM and C/N), as well as the plant N recovery, the IWUE, and the NAE. They increased the water retention capacity of the soil when the tobacco crop was deficit-irrigated and appeared to be promising practices to support the deficit irrigation strategy, contributing to reaching good agronomic results, although under the conditions of water shortage, and showing synergistic action in those conditions.