Acidification of soil associated with lupins grown in a crop rotation in north-eastern Victoria

Abstract

Soil pH decline and net acidification inputs were determined for a long-term crop rotation experiment at Rutherglen in north-eastern Victoria. The rotations utilized were continuous wheat (WW), a 1 : 1 wheat-lupin sequence (WL) and continuous lupins (LL), and each rotation was cropped from 1975-1989. The soil at the site had an initial pH (0.01 mol/LCaCl2) of 6.0 (0-10 cm depth), sandy loam texture, and had a past use of grape vines and then lucerne pasture. The soil pH (0-10 cm) declined for each rotation with time (1977/78-1988/89), decreasing by about 0.8 units for WW and further decreasing with the inclusion of lupin in the rotation. Compared with the WW soil, the WL soil pH was 0.7 and 0.4 units lower at 5-10 cm and 10-15 cm depth and the LL soil pH was 1.0 and 0.8 units lower at 5-10 and 10-15 cm depth. There was no difference in pH between WW and WL below 20 cm depth, but the LL soil had a significantly lower pH to 40 cm depth. Acidification rates were calculated for the period of cropping and for the 3 rotations, with rates of 3.22, 4.11 and 5.26 kmols H+/ha.yr as net acid input for WW, WL and LL rotations. These values represent a rapid rate of soil acidification. The removal of alkalinity in grain accounted for between 15-21% of the overall calculated acidification rate for the 3 rotations. Therefore, it is likely in this cropping system that the acidification largely results from progressive nitrate leaching.

Aluminium cycling in the soil-plant-animal-human continuum

“…Most soils are being acidified continuously due to (i) imbalances in nitrogen, sulphur and carbon cycles (Bolan & Hedley 2003;Tang & Rengel 2003), (ii) excess uptake of cations over anions (Tang & Rengel 2003), (iii) use of ammonia-and amide-containing fertilizers (Mahler et al 1985), (iv) nitrogen-fixation by legumes (Bolan et al 1991;Coventry & Slattery 1991;Tang & Rengel 2003), and (v) acidic depositions from the atmosphere (Alewell 2003).…”

Aiuminium tolerance of durum wheat germplasm

“…Continuous use of ammoniaand amide-containing fertilisers (Mahler et al ., 1985) or nitrogen-fixation by legumes (Boland et al ., 1991 ;Coventry & Slattery, 1991) causes soil acidification and aggravates Al toxicity thus contributing to an increase in the soil acidity and enhanced Al solubility in 'acid-sensitive' soils (for references see Rengel, 1992) .…”

Role of calcium in aluminium toxicity

“…Over the years following the initial report, Al has become recognized as the most limiting factor in many acid soils throughout the world (Foy, 1988), possibly affecting about 40 °o and perhaps up to 70 °o of the world's arable land that is potentially usable for food and biomass production (Haug & Caldwell, 1985;and references tberein). Soil acidification resulting from either continuous use of ammonia-and amide-containing fertilizers (Mahler, Halvorson & Koehler, 1985) or the nitrogen-fixation by legumes (Bolan et al, 1991;Coventry & Slattery, 1991) aggravates Al toxicity and contributes to an increase in the soil area affected. In addition, the recent advent of acid precipitation (Johnson et al, 1981) has increased soil acidity (Kuylenstierna & Chadwick, 1991) and enhanced Al solubility in 'acid-sensitive' soils (FalkengrenGrerup, 1987), thus aggravating Al toxicity, especially in forest stands (Cronan et al, 1989).…”