Properties of soil aggregates as influenced by tillage practices

Abstract

Abstract. Changes in aggregate stability, density, and porosity as well as the water retention and nutrient contents of different aggregate size fractions due to intensive tillage were investigated. Three soils from Vicarello, Fagna and Gambassi in North Central Italy which had been under permanent vegetation, minimum or conventional tillage for more than seven years were studied. The aggregates on conventionally tilled plots were slightly denser and less porous than those on the untilled or minimum‐tilled plots. The aggregates were less stable under conventional tillage on all soils. Conventional tillage reduced the proportion or macro‐aggregates by 22% at Vicarello and 35% at Gambassi. There were no differences in macro‐aggregate proportions between minimum‐ and conventionally tilled plots at Fagna. The potential of the dry aggregates to distintegrate upon contact with water was greatest in the conventionally tilled and least in the untilled treatments. The proportions of dry macro‐aggregates (> 0.25 mm) in the untilled and tilled plots were 90 and 71%, respectively. The soil of the tilled plots contained less carbon and nitrogen than that of the untilled plots in all aggregate size fractions. The silt‐plus‐clay contents of the aggregates accounted for between 65 and 93% of variability in the water they retained at small potentials while organic carbon contents accounted for between 71 and 90% of variability in the stability of the aggregates irrespective of the tillage treatments.

Aggregate stability of four soils as evaluated by different indices

“…Furthermore, good soil management under cultivated conditions could significantly reduce the degree of aggregate break do wn. T hat is contrary to the observation of Moreau (1978), that aggregate stability is reduced by cultivation. T he mixed crop culture observed in the studied soils might have influenced the nature of the result obtained.…”

“…degree of resistance against disintegrating forces of water and physical action) is most important factor in the structural behavior of a soil. Cultivation is one of the major factors that break the defensive measure of the soil structural aggregates, so soil structural stability usually decrease d with cultivation (Moreau, 1978;Six et al, 2000;Eynard et al, 2004). Similarly, Babalola & Chielda (1972) and Kowalinski et al (1982) reported that cultivated soils were less stable and have predominantly small aggregates compared with the virgin soils.…”

“…Contradictory opinion were given by Holepla ss et al (2004) and Khurshid et al (2006) that soil aggregations are strongly influenced by tillage related practices. Nevertheless, the mean-weight diameter of dry aggre gate is not very sensitive in detecting differences among various land use type (Mbagwu & Bazzoffi, 1989).…”

“…When stability is measured under relatively wet condition, it is noted that it is decreasing with water content (Kay & Dexter, 1990;Perfect et al, 1990;Gollany et al, 1991). The ability of the dry aggre gates to disintegrate upon contact with water was noticed to be greatest in the conventionally tilled and least in the untilled soils (Mbagwu & Bazzoffi, 1989). Pagliai (2005) observed that stable macro-aggregate in wet sieving of tilled soil is lo wer than that of no tilled soil due to aggregate break do wn in tillage process.…”

Infiltration and Soil Properties as Affected by Annual Cropping in the Northern Great Plains

“…Organic C accounted for about 70 to 90% of the variability in soil aggregate stability of a clay loam soil (Mbagwu and Bazzoffi, 1989). Bruce et al (1992) determined that increased phytomass input to a loamy sand increased aggregate stability and water infiltration.…”