Abstract
Two spinach (Spinacea oleracea L.) cultivars were evaluated for their response to deficient (0.25 mmolc L−1 or 0.25 K) and sufficient (5.0 mmolc L−1 or 5.0 K) potassium (K) levels combined with salinities of 5, 30, 60, 90, and 120 mmolc L−1 NaCl. Plants substituted K for Na proportionally with salinity within each K dose. Plants favored K+ over Na+, regardless of salinity, accumulating significantly less Na at 5.0 K than at 0.25 K. Salinity had no effect on N, P, and K shoot accumulation, suggesting that spinach plants can maintain NPK homeostasis even at low soil K. Ca and Mg decreased with salinity, but plants showed no deficiency. There was no Na+ to K+ or Cl− to NO3− competition, and shoot biomass decrease was attributed to excessive NaCl accumulation. Overall, ‘Raccoon’ and ‘Gazelle’ biomasses were similar regardless of K dose but ‘Raccoon’ outproduced ‘Gazelle’ at 5.0 K at the two highest salinity levels, indicating that ‘Raccoon’ may outperform ‘Gazelle’ at higher NaCl concentrations. At low K, Na may be required by ‘Raccoon’, but not ‘Gazelle’. This study suggested that spinach can be cultivated with recycled waters of moderate salinity, and less potassium than recommended, leading to savings on crop input and decreasing crop environmental footprint.
Highlights
Soil quality and water salinity are major problems for the environment and for food production.Salinity occurs in arid and semi-arid zones of every continent, except Antarctica [1]
We hypothesized that spinach growth was going to be significantly reduced in response to high salinity and potassium deficiency, mainly when combined through the irrigation water
In the treatment with sufficient K (5.0 mmolc L−1 ), K was provided in the irrigation water
Summary
Salinity occurs in arid and semi-arid zones of every continent, except Antarctica [1]. As both water and soil salinity increase, water and nutrients absorbed by plants decrease due to osmotic effects. Under saline conditions, important nutrients remain dissolved in the soil matrix, where they may be lost to the environment through leaching. Salts present in saline soils can occur typically, naturally or as residue of fertilizers, as Na+ , −. Na accumulates in most plant tissues at similar concentrations as N and K but is not considered an essential nutrient for glycophytic plants. Na is preferentially absorbed compared to K and, under salinity, Na+ inhibits K+ uptake and displaces K+ from its cellular binding sites [6] and can become cytotoxic
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