The role of mineral nutrients in the increased growth response of tomato plants in solarized soil

Soil solarization is a non-chemical disinfestation technique that frequentl y promotes plant growth in the absence of known major pathogens, a phenomen on termed increased growth response (IGR). The effect of solarization on pl ant nutrients and their role in the IGR was studied with tomato plants grow n in solarized or non-solarized (control) sandy soil, under controlled cond itions. Solarization considerably increased the soil concentrations of wate r extractable N, K, Ca, Mg and Na at most sites, whereas Cl and DTPA extrac table Mn, Zn, Fe and Cu were decreased by the treatment. Plant growth and s pecific leaf area were enhanced in solarized as well as in N-supplemented c ontrol soil. In tomato plants grown in solarized soil, concentrations of mo st nutrients in the xylem sap, including N, were increased compared to the control, whereas Cl and SO4 levels decreased. The most significant increase in leaf nutrient concentration caused by soil solarization was recorded fo r N. Furthermore, leaf N concentration was highly and positively correlated with shoot growth. The concentration of Cu increased in leaves from the so larization vs. the control treatment, whereas that of SO4 and Cl decreased, the latter presumably below the critical toxicity level. The correlation b etween shoot growth and leaf concentration was positive for Cu and inverse for Cl and SO4. In conclusion, we found that soil solarization significantl y affects nutrient composition in tomato plants, and provided strong eviden ce that N, and eventually also Cl, play a major role in IGR.