Soil structural stability following decades of straw incorporation and use of ryegrass cover crops

In conservation management systems, such as no-till (NT), it is important to analyze the pattern of changes in soil quality as a function of the time since adoption of the system. This study evaluated the physical fractions of organic matter and soil aggregation in management systems in areas cultivated with different times since implementation of NT: 6, 14, and 22 successive years of soybean and maize/wheat crops (NT6, NT14, and NT22, respectively); 12 years of no-till with successive years of soybean and maize/wheat crops, and the last 4 years with integration of maize and ruzi grass (Brachiaria ruziziensis) - (NT+B); pasture; and forest. Physical fractionation of organic matter determined the total carbon (TC), particulate organic matter (POM), and mineral organic matter (MOM) by calculating the carbon management index (CMI) and variables related to soil structural stability. Forest and pasture areas showed the highest contents of TC, POM, and MOM, as well as higher stocks of POM and MOM. Among the cultivated areas, higher TC and particulate fractions of organic matter and the best CMI values were observed in the area of NT22. There were changes in aggregation indices, depending on the time since implementation of NT. Areas of NT22, pasture, and forest showed the greatest evolution in C-CO2, indicating increased biological activity, with positive effects on soil structural stability.

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Cation ratio of soil structural stability (CROSS)

Soil Research ◽

10.1071/sr10105 ◽

2011 ◽

Vol 49 (3) ◽

pp. 280 ◽

Cited By ~ 84

Author(s):

Pichu Rengasamy ◽

Alla Marchuk

Keyword(s):

Hydraulic Conductivity ◽

Structural Stability ◽

Control Treatment ◽

Recycled Water ◽

Clay Dispersion ◽

Soil Structural Stability ◽

Salt Affected Soils ◽

Highly Correlated ◽

Irrigation Waters ◽

Cation Ratio

Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium adsorption ratio (SAR) is used to parameterise soil sodicity and the effects of sodium on soil structure. However, some natural soils in Australia, and others irrigated with recycled water, have elevated concentrations of potassium and/or magnesium. Therefore, there is a need to derive and define a new ratio including these cations in place of SAR, which will indicate the dispersive effects of Na and K on clay dispersion, and Ca and Mg on flocculation. Based on the differential dispersive effects Na and K and the differential flocculation powers of Ca and Mg, we propose the concept of ‘cation ratio of soil structural stability’ (CROSS), analogous to SAR. This paper also gives the results of a preliminary experiment conducted on three soils varying in soil texture on hydraulic conductivity using percolating waters containing different proportions of the cations Ca, Mg, K, and Na. The relative changes in hydraulic conductivity of these soils, compared with the control treatment using CaCl2 solution, was highly correlated with CROSS. Clay dispersion in 29 soils treated with irrigation waters of varying cationic composition was highly correlated with CROSS rather than SAR. It was also found that CROSS measured in 1 : 5 soil/water extracts was strongly related to the ratio of exchangeable cations. These results encourage further study to investigate the use of CROSS as an index of soil structural stability in soils with different electrolytes, organic matter, mineralogy, and pH.

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Amending soil with sludge, manure, humic acid, orthophosphate and phytic acid: effects on aggregate stability

Soil Research ◽

10.1071/sr13334 ◽

2014 ◽

Vol 52 (4) ◽

pp. 317 ◽

Cited By ~ 11

Author(s):

A. I. Mamedov ◽

B. Bar-Yosef ◽

I. Levkovich ◽

R. Rosenberg ◽

A. Silber ◽

...

Keyword(s):

Humic Acid ◽

Phytic Acid ◽

Structural Stability ◽

Organic Amendments ◽

Aggregate Stability ◽

Loamy Sand ◽

Soil Aggregate Stability ◽

Before And After ◽

Soil Structural Stability ◽

The Stability

Recycling of organic wastes via their incorporation in cultivated lands is known to alter soil structural stability. Aggregate stability tests are commonly used to express quantitatively the susceptibility of soil structural stability to deformation. The objective of this study was to investigate the effects of biosolids addition, namely composted manure (MC) and activated sludge (AS), and spiking of the soils with orthophosphate (OP), phytic acid (PA) or humic acid (HA), on soil aggregate stability of semi-arid loamy sand, loam and clay soils before and after subjecting the soils to six rain storms (each 30 mm rain with a break of 3–4 days). Aggregate stability was determined from water-retention curves at high matric potential. The effects of the applied amendments on pre- and post-rain aggregate stability were inconsistent and soil-dependent. For the pre-rain state, all of the tested amendments improved aggregate stability relative to the control. For the post-rain condition, aggregate stability was lower in the MC, OP and PA treatments and higher in the AS and HA treatments than in the control. The coarse-textured loam and loamy sand soils were more affected by the soil amendments than the clay soil. For the pre-rain state, addition of organic matter significantly improved macro-porosity and hence the stability of apparent macro-aggregate (>250 μm). Our results indicate a possible advantage for separation of aggregates into macro- and micro-aggregates for more precise evaluation and understanding of the effects organic amendments might have on aggregate stability.

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