Ameliorating Chlorosis‐Inducing Soils with Rock Materials of Varying Porosity and Iron Content

Lime‐induced chlorosis is a severe problem, affecting many crops in arid‐ and semiarid‐zone soils. Applications of Fe chelates are expensive and only effective in the short term. The ameliorating effects of rock materials on three chlorosis‐producing calcareous soils from Israel were determined in pot tests and in the field. Chlorophyll concentrations of peanut plants ( Arachis hypogaea L.) grown in pots with additions of up to 15% (v/v) pumice or tuff‐lapilli to the soils were compared with controls and Fe‐ethylenediaminedihydrochloric acid (EDDHA) treatments. Additions of 10% (v/v) tuff‐lapilli were more effective than those of pumice in small‐pot tests of all three soils. Positive effects persisted for a second growth period. In large‐pot tests, only 15% (v/v) additions were effective in two soils. In field tests, the three soils were treated with pumice or tuff‐lapilli (10% v/v) or basalt powder (5.5% w/w). Basalt powder was the most effective in raising chlorophyll concentrations to levels similar to or greater than those obtained from Fe‐EDDHA. Basalt powder was also the most effective in increasing pod and hay yields on two soils. Also, basalt appeared to have long‐term effects. Only where chlorosis was not severe and where poor aeration appeared to be an additional factor were the effects of tuff‐lapilli and pumice equal or even superior to those of basalt powder. On two soils with severe chlorosis, addition of porous, Fe‐poor materials had no effect. Either because the soils were well aerated or because CO 2 production was low, CO 2 in the soil air was low and not a major factor determining HCO 3 ‐ in water extracts.