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This article in SSSAJ

  1. Vol. 51 No. 4, p. 970-974
    Received: Aug 27, 1986

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Phosphorus and Potassium Uptake by Corn in Conservation Tillage Systems1

  1. A. D. Mackay,
  2. E. J. Kladivko,
  3. S. A. Barber and
  4. D. R. Griffith2



In conservation tillage systems surface application of P and K fertilizers and the annual return of corn residue to the soil surface can result in the stratification of these two nutrients in the topsoil. The extent to which this changes P and K uptake patterns of corn (Zea mays L.) has not been investigated. The objectives of this field study on a Chalmers silty clay loam (Typic Haplaquoll) were to compare the degree of stratification of P and K after 9 yr under conventional, no-till, and ridge till systems, and to use this data along with root measurements in a model to calculate P and K uptake patterns by corn under these three tillage systems. Under conventional tillage Bray P1-P and exchangeable K were distributed evenly throughout the topsoil (0–275 mm). Stratification of P and K, however, had occurred in the ridge till and no-till systems after 9 yr. Of calculated P and K uptake from 30 to 47 d after planting, only 18 and 23%, respectively, came from the upper 75 mm under conventional tillage, compared with 52 and 58%, respectively, under no-till for the same period. From 30 to 77 d, 39 and 52% of calculated P and K uptake, respectively, was from the upper 75 mm under no-till compared with only 28 and 26%, respectively, under conventional tillage. Some deep placement of fertilizer P and K may be desirable after several years of continuous no-till cropping, to provide P and K to roots growing deeper in the soil.

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