Zeolite and Ascophyllum nodosum-Based Biostimulant Effects on Spinach Gas Exchange and Growth

Among the innovative practices of dry-farming in recent years, the possibility of the combined use of biostimulants and soil conditioners is assuming an important role. In a preliminary pot experiment, this study aimed to verify the combined effects of Ascophyllum nodosum-based biostimulant and zeolite applied to the soil on gas-exchange and spinach growth. We also monitored the soil water content to study the effect on spinach soil water uptake. Pots were filled with soil to which zeolite and an Ascophyllum nodosum-based biostimulant were added. Spinach plants grew into pots and were subjected to four treatments: (1) soil plus zeolite at a percentage of 1%, (2) soil plus the biostimulant, (3) soil plus zeolite at 1% and biostimulant, (4) bare soil as control. The use of the zeolite and the A. nodosum-based biostimulant led to a higher (+10%) soil water content, highlighting the positive role in allowing a good water uptake by the spinach plant. Plant growth was not changed, while only photosynthesis showed an increase equal to 6% in spinach plants. These results are discussed with the soil water content variation according to modification induced by treatments. The combined use of zeolite and A. nodosum-based biostimulant can be considered a strategy to improve water storage and, at the same time, improve spinach cultivation in terms of sustainability.