TOPSOIL AND SUBSOIL POTASSIUM AS AFFECTED BY LONG-TERM POTASSIUM FERTILIZATION OF CORN-SOYBEAN ROTATIONS

Citation
Ap. Mallarino et M. Ulhaq, TOPSOIL AND SUBSOIL POTASSIUM AS AFFECTED BY LONG-TERM POTASSIUM FERTILIZATION OF CORN-SOYBEAN ROTATIONS, Communications in soil science and plant analysis, 28(17-18), 1997, pp. 1537-1547
Citations number
18
Categorie Soggetti
Agriculture Soil Science","Plant Sciences","Chemistry Analytical
ISSN journal
00103624
Volume
28
Issue
17-18
Year of publication
1997
Pages
1537 - 1547
Database
ISI
SICI code
0010-3624(1997)28:17-18<1537:TASPAA>2.0.ZU;2-S
Abstract
Long-term potassium (K) fertilization practices are likely to affect t he K content of soils. This study assessed the effect of long-term K f ertilization strategies for corn (Zea mays L.) and soybean [Glycine ma x (L.) Merr.] rotations on extractable K in the soil profile of a majo r Iowa soil type at two locations. The soil type was a Webster fine-lo amy, mixed, mesic, Typic Haplaquoll at both sites. Soil samples were c ollected from the 0-15, 15-30, 30-60, and 60-90 cm depths after 17 yea rs (Site 1) or 19 years (Site 2) of K fertilization with combinations of two initial rates and four annual rates. The initial rates were 0 a nd 1,344 or 1,120 kg K ha(-1) at Site 1 and 2, respectively, and the a nnual rates ranged from 0 to 100 kg K ha(-1). Samples were analyzed fo r ammonium acetate-extractable K (STK) and nitric acid (HNO3)-extracta ble nonexchangeable K (HNO3-K). Concentrations of STK and HNO3-K in th e top 0-15 cm soil layer at the two sites were higher for the high ini tial K rates and were linearly related with the annual K rate. Results for the subsoil layers varied between sites and extractants. At Site 1, annual rates of 30 kg K ha(-1) or higher resulted in a relative acc umulation of HNO3-K in the 15-30 cm layer. At Site 2, these rates resu lted in relative accumulations of STK in the 30-60 cm layer and of HNO 3-K in the 60-90 cm layer, but with relative depletions of STK in the 15-30 and 60-90 cm layers. Thus, use of one extractant may not always be sufficient to evaluate cropping and fertilization effects on subsoi l K. Long-term K fertilization of corn and soybean rotations affected extractable K of both the topsoil and subsoil. The effects on subsoil K, however, were smaller compared with effects on the topsoil and vari ed markedly between sites, subsoil layers, and extractants.