Open AccessSTUDIES ON THE POTASSIUM-SUPPLYING CAPACITIES OF SOUTHERN ONTARIO SOILS. I. FIELD AND GREENHOUSE EXPERIMENTS
Author(s) -
John E. Richards,
T. E. Bates,
Stephen Sheppard
Publication year - 1988
Publication title -
canadian journal of soil science/canadian journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 67
eISSN - 1918-1841
pISSN - 0008-4271
DOI - 10.4141/cjss88-019
Subject(s) - soil water , greenhouse , potassium , agronomy , chemistry , environmental science , zoology , soil science , biology , organic chemistry
The response of grain corn (Zea mays L.) to applied K was studied for 10 yr on three southern Ontario soils. On a Conestogo L, the most profitable rate of K application was 2.5 times higher than expected and the critical concentration of NH 4 OAc-K, above which no response occurred to either applied K or increasing NH 4 OAc-K concentrations, was higher (2 ×) than expected, based on 1 M NH 4 OAc-extractable K and interpretation by the Ontario Ministry of Agriculture and Food soil test. All soils fixed substantial quantities of applied K, but the amount fixed by the Conestogo L was not greater than that fixed by the other two soils. When no K was applied, corn removed less nonexchangeable K (NEK) from the Conestogo L than from the other two soils. A greenhouse experiment was conducted to determine if either the availability of NH 4 OAc-K or NEK to alfalfa (Medicago sativa L. 'Banner') was lower on highly responsive soils than on less responsive soils. By the end of the experiment, soils on which crops were very responsive to applied K (Guelph L, Conestogo L, and Teeswater SiL) had supplied less K to alfalfa than had soils (Brookston L and Fox SL) on which response to applied K in field trials was similar to that predicted by the soil test. Total K uptake was related to NEK uptake suggesting that differences in the K-supplying capacities of the soils were associated with the availability of NEK to alfalfa. It was concluded that the responses to higher rates of applied K than expected in field trials were due to lower uptake of NEK. The clay mineralogy of the soils was dominated by illite with lesser amounts of vermiculite. No appreciable differences in mineralogy were found between the two groups of soils and NEK uptake was not significantly related to the amount of clay nor to the illite content of the coarse clay and fine clay fractions. Key words: NH 4 OAc-K, nonexchangeable K, illite, vermiculite, alfalfa, corn