Plant and Soil 73, 155-158 (1983). Ms. 5306 9 1983 Martinus Nijhoff/Dr IV. Junk Publishers, The Hague. Printed in the Netherlands. Ground basalt and tuff as iron fertilizers for calcareous soils PHILLIP BARAK, YONA CHEN and ARIEH SINGER Seagram Centre for Soil and Water Sciences, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel Received 16 December 1982. Revised March 1983 Key words Basalt Chlorosis Iron fertilizer Peanuts Tuff Summary Crushed basalt and tuff were found to significantly improve the iron nutrition of peanuts grown in pots of highly calcareous soil. At a rate of 89 powdered rock (by weight), chlorophyll contents were double those of plants grown in untreated soil. At rates of 5~o by weight, the effect of the rock powders was equal to that of FeEDDHA. The effectiveness of the rock powders was lower in the second crop on the same soils. Introduction Chlorosis due to iron deficiencies in agricultural plants is relatively common in calcareous soils, hence the term "lime-induced chlorosis"; in extreme cases, iron deficiencies may lead to complete crop failure 3. Treatment of iron deficiency usually entails either soil application of synthetic organic chelates, such as FeEDDHA or FeDTPA, or periodic foliar application of iron salts. Ground rocks and minerals have been widely used as fertilizers for macronutrients such as calcium (lime, dolomite and gypsum), magnesium (dolomite, kieserite and serpentine), potassium (glau- conite, feldspar, basalt and granite), sulfur (gypsum, pyrite and elemental sulfur), and phosphorus (phosphate rock). This communication presents results of experiments conducted to determine if crushed basalt and lapilli tuff (pyroclastic deposits of volcanic ash and larger vesicular fragments), byproducts of local quarrying operations, are useful as fertilizers for iron and remedying lime-induced chlorosis. Materials and methods Peanuts (Arachis hypogaea L. cv "Shulamit") were grown in pots containing 500 g of a rendzina soil from Mitzpeh Massua, (light clay, 63~o CaCO3, 34~ active lime, pH 7.8, 1.1 ppm DTPA-extractable Fe, and 0.2~0 dithionite-extractable Fe) in a conventional growth chamber. Basalt and tuff powders, with characteristics as listed in Table 1 and a mineralogy as detailed by Singer8, were thoroughly mixed into the soil at rates of 0 to 5~o by weight. As an additional check, one treatment received 2 mg iron per kg soil as FeEDDHA added to the irrigation water; this amount was sufficient to completely eliminate chlorosis. At 35 days, plants were harvested and chlorophyll was extracted in 80~o acetone and determined spectroscopically. After the first harvest, plant residues were removed and soils were air-dried for 50 days. A second crop of peanuts was grown in the same pots to test residual fertilizing effects and was harvested in th~ same manner. A fresh FeEDDHA treatment was included in the second crop as an additional check. Each treatment consisted of five pots with two plants in each. Further experimental details are presented elsewhere I. 155