Changes in aggregate stability and associated organic matter properties after direct drilling and ploughing on some Australian soils

Abstract

After 3-8 years' continuous cropping with conventional cultivation and direct drilling, five Australian soils were examined for changes in structural stability attributable to tillage methods. Some increase in organic carbon was found in four direct drilled soils, and the proportion of carbon in the greater than 2 �m fractions was also higher in these soils after short ultrasonic treatment. Direct drilled soils had significantly greater stability with at least one of the stability tests used, but no soil showed consistently greater stability to five different tests. One direct drilled soil was more stable than its ploughed equivalent after alkaline and neutral salt extraction of metal ions and associated humic substances. One direct drilled soil was more dispersed by polysaccharide extraction. Three direct drilled soils retained greater stability after selective extraction of trivalent metal ions complexed to humic fractions. Structural improvement takes place in Australian soils after several years of direct drilling, but may be at a slower rate and to a lesser extent than has been reported for wetter environments.

The influence of alternative tillage systems on the distribution of nutrients and organic-carbon in some common Western Australian wheatbelt soils

“…However, interestingly, the organic C concentration decreased steadily throughout the duration of the experiment, even when direct drilling was used. This is in contrast to results obtained on some other Australian soils (Hamblin 1980) and suggests that continuously cropping this soil type, even with direct drilling, is producing a very fragile soil structure that may still be declining. The structural stability of the soil will decline via a reduction in the organic C concentration per se (including positional changes in the organic C) and also indirectly via a reduction in the soil fauna and flora populations which are reliant on the organic C as a source of energy.…”

“…In many situations in Australia, reduced cultivation will stabilize soil structure and minimize erosion of intensively cropped soils (Greenland 1971;Hamblin 1980Hamblin , 1987Negus 1980). However, reduced cultivation, when compared with conventional cultivation, has either increased, decreased or had no effect on the growth of the crop and its subsequent yield (see Table 1).…”

Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

“…This can be measured by the decrease in aggregate stability (Carpenedo & Mielniczuk, 1990;Da Ros et al, 1997;Silva & Mielniczuk, 1997D'Andréa et al, 2002). Among tillage systems, aggregate stability in the surface layer under no-till is usually greater than in conventional tillage systems (Hamblin, 1980;Carpenedo & Mielniczuk, 1990;Campos et al, 1995;Castro Filho et al, 1998;Beutler et al, 2001;D'Andréa et al, 2002), but in both soil aggregates may be compacted, with predominance of micropores (Carpenedo & Mielniczuk, 1990).…”

Effect of Tillage Reduction and Fertilizer on Soil Macro- And Microaggregation

“…These aggregates are rich in organic matter and highly stable in water. The 2O-25O (Klute and Jacob 1949;Doyle and Hamlyn 1960;Mazurak et al 1977) and the larger organic matter content of zero-tilled soils promotes aggregation and aggregate stability in the surface layer Hamblin 1980 (Mazurak 1950) and aggregation index (AI) (Dobranski et al 1975; MacRae and Mehuys 1987) were then calculated.…”