A greenhouse investigation to evaluate the effects on plant growth of incorporation of high rates (2.5% or 10% by weight of soil) of paper mill sludge material from several primary and secondary treatment processes was conducted. Sludges from secondary biological treatment processes contained sufficient N in relation to organic C (range of C/N values was 12:1–50:1) so that N was not limiting to plant growth. However, sludges from primary treatment processes contained high organic C/N ratios (ca. 150:1) and would require considerable supplementary N fertilizer if cereal crops or grasses were to be planted soon after sludge application. At the high sludge rate, plant growth was diminished even though sufficient fertilizer N, P and K had been applied.

Samples from Ap horizons of 36 cultivated Wisconsin fields were tested for concurrent availabllity of Cu, Zn and Mn. The effects of soilpH, organic matter, and available P were evaluated by using four chemical extractants. Oats were used as the test crop and were grown using a self-wateringpo~-culture technique in a plant-growth room. The divergent soils had the following averages: pH, 6.4; organic matter, 2.6%; available P, 37 ppm; total Cu, 20 ppm; total Zn, 35 pprn; and total Mn, 631 pprn. Concentrations

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The interrelationships of the amounts of Cu, Zn and Mn extracted with four chemical extractants of varying p H and buffering capacities, and as influenced by soil p H , organic matter, and available P, were evaluated. Regression equations using 0. I N-HCI, 0.01 M EDTA, and 0.005 M DTPA soil-extractable fractions in conjunction with the soil properties for the estimations of total Cu, Zn and Mn in divergent Wisconsin soils are afso given. The relationship of the Mg(NO3)a-extractable fractions of the three elements to the above four fractions were better defined by quadratic than by linear equations. Exchangeable Zn had positive white exchangeable Mn had negative influence on exchangeable Cu in these soils with widely varying Cu supply. Both exchangeable Cu and Mn increased Mg(NO3)a-extractable Zn, whereas exchangeable Cu depressed the Mg(NO~)z-extractable soil Mn.

A wick culture technique for growing plants in potted soils was developed. In the method described, about 50 oat (Avena sativa L.) seeds are sown to a pot and are grown under plant‐growth room conditions for about 4 weeks. Water for the plants is supplied entirely by a fiberglass wick extending from the center of the pot into a glass cylinder. The technique is especially adaptable to micronutrient element studies. It has several advantages over the ordinary pot culture techniques for growing plants. The construction materials are available and inexpensive.