| Abstrakt: |
A long‐term experiment using corn (Zea maysL.) was initiated in 1973 on calcareous strip‐mine spoil to evaluate the effects of anaerobically digested sewage sludge on the spoil‐crop system. Treatments consisted of a check (336‐224‐112 kg ha−1year−1N‐P‐K) and sewage sludge applications, weather permitting, at weekly rates of 0.64, 1.27, and 2.54 cm. In 5 years, 1973–1977, a total of 258 dry t ha−1sludge was applied to maximum treatments. Grain yields were significantly affected by sludge application in some years, but stover yields were not affected. Concentrations of N, P, K, Ca, and Mg in corn tissue varied in response to sludge applications. Leaf and grain P and grain K declined with higher rates of sludge application. The total uptake of the five elements by corn did not generally vary with the treatments, although there were yearly differences in uptake. Factors affecting plant nutrition were investigated. Negative interactions were observed between leaf N and Mg and stover P and Zn. An evaluation of plant nutrient balance by the Diagnosis Recommendation Integrated System (DRIS) suggested that the order of required elements in corn from sludge treatments was most often P > K > N > Ca > Mg. For check treatments receiving only commercial fertilizer, the order of required nutrients was usually K > N > Ca > P > Mg. Considerable amounts of P were applied annually (365–2,690 kg ha−1) to maximum‐amended plots, and excessive P accumulation by corn may have been reduced by reactions with metals in the applied sludge, spoil, and plant tissue, and by a dilution effect from increased plant matter production. Spoil factors (e.g., shallow rooting, soluble salts, and moisture stress) and plant element and/or spoil element interactions were important variables reacting with existing climatic conditions to influence corn yields and nutrient compositions. |
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