Agro-Ecological Impact of Irrigation and Nutrient Management on Spinach (<i>Spinacia oleracea</i> L.) Grown in Semi-Arid Conditions

The environment is affected by most anthropogenic activities; among them, agriculture is one activity with more negative effects, especially when management is inadequate, causing soil degradation or contamination. This paper presents the results of an agronomic field trial on a spinach (Spinacia oleracea L.) crop. The objective of which was to monitor soil and crop properties under two doses of irrigation and organic fertilization. The results showed that the use of excessive doses of irrigation and fertilization increased the electrical conductivity (ECext) from 5.5 to 8.5 dS m−1 and the concentration of ions in the soil solution which, for the most soluble ions (NO3−, Cl−, Na+), leached towards the deep horizons, reaching 2194.8 mg L−1 in the case of NO3−. However, their use did not increase spinach production and is thus a waste of resources that increases the risk of soil salinization. Nutrient inputs to the soil were much higher than extractions (between 12% for N and 99% for Fe), partly because of agronomic management and especially because of the return of crop residues, which increased the organic carbon stock by about 2500 kg ha−1 (4–6%), enhancing its function as a CO2 sink. These surpluses form part of complex organic structures or are immobilized as carbonates or alkaline phosphates. Preservation of the agrosystem studied requires limiting the use of low-quality irrigation water and adjusting fertilization