Acid-subsoil amelioration. I. A comparison of several mechanical procedures
Farina, M.P.W. | Channon, P.
In many high potential cropping areas, particularly of the tropics and subtropics, crop exploitation of subsoil moisture reserves is prevented or severely curtailed by high levels of exchangeable Al. Since the effects of surface incorporated lime on subsoil acidity are minimal in most highly weathered soils, specialized mechanical and/or chemical procedures are required to overcome the problem. This work was conducted in order to assess the practicalities of mechanical profile modification and to compare the efficacy of several possible procedures. In a field experiment with maize (Zea mays L.) on a strongly acidic Plinthic Paleudult conventional moldboard incorporation of lime was compared to lime incorporation using a deep moldboard plow, the Wye-double-digger, a modified subsoiler capable of incorporating vertical bands of ameliorated topsoil to depths of 0.7 m, and a deep limer designed to ameliorate vertical bands of soil to a similar depth. All the procedures tested proved superior to conventional liming, the average response to profile modification ranging from over 1 400 kg ha-1 in a season in which severe moisture stress was experienced to approximately 400 kg ha-1 in an exceptionally high rainfall season. Yield responses were related to increases in rooting volume and to changes in root configuration. Segmental liming proved as effective as deep plowing or double digging.
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