Effect of liquid humus and calcium sulphate on soil aggregation

Abstract

An Ultic Haploxeralf soil collected from ridges built into the slopes of the Coastal Mountain Range of Central Chile was used in applications of humic and fulvic acids (HFA) extracted from sludge from sewage treatment plants, in combination with gypsum (CaSO 4 ). A total of 12 treatments were applied by combining four doses of HFA (0, 20, 30 and 40 t ha -1 ) with three doses of gypsum (0, 1.2 and 6.0 t ha -1 ). The effect of these treatments was assessed using three indicators of the degree of soil aggregation: macroporosity (MA), bulk density (Da) and microinfiltration (MI). The experiment was set up in a laboratory using a completely randomised design (CRD). Factorial variance analysis was also performed using two factors: gypsum in three doses and HFA in four doses. For all three indicators, MA, Db and MI, it can be seen that there is interaction between the HFA treatments and the gypsum treatments in the studied soil. The macroporosity increased with HFA treatments with 20 or 30 t ha -1 (9%) and with gypsum of 1.2 t ha -1 plus 20 t ha -1 HFA (11%). It can also be seen that the gypsum treatments have no effect on Db when HFA is not applied. Microinfiltration is the variable that shows the greatest effects from the treatments applied. The results also clearly show that high amounts of HFA (40 t ha -1 ) and of gypsum (6.0 t ha -1 ) cancel out the differential effects and cause negative effects on the three indicators for the studied soils. The use of liquid humus and its combination with calcium sulphate (20/1.2 t ha -1 ) improves soil aggregation.

The effect of four calcium‐based amendments on soil aggregate stability of two sandy topsoils

“…In addition, the weak aggregation response shown by CaCO 3 is also similar to that reported by Chan and Heenan (1998), who observed a change in the structural stability of the soil only three years after the application of CaCO 3 . However, our results contrast with those reported by Baldock et al (1994) and Norambuena et al (2014). Specifically, both studies reported a significant increase in aggregate stability when simultaneously applying organic matter, CaSO 4 and CaCO 3 (Baldock et al, 1994) and when applying liquid humus with CaSO 4 (Norambuena et al, 2014).…”

“…However, our results contrast with those reported by Baldock et al (1994) and Norambuena et al (2014). Specifically, both studies reported a significant increase in aggregate stability when simultaneously applying organic matter, CaSO 4 and CaCO 3 (Baldock et al, 1994) and when applying liquid humus with CaSO 4 (Norambuena et al, 2014).…”

“…However, it would be prudent to carry out field studies on the effect of Ca(OH) 2 on growth of crops sensitive to salinity. Finally, Ca(OH) 2 as a water soluble product could be applied with irrigation water, making its distribution in the soil more efficient, particularly on hillsides that are more prone to erosion ( Youlton et al, ; Norambuena et al, ).…”

“…Consequently, from an agricultural point of view, Ca(OH) 2 would be a feasible soil amendment to use for improving aggregate stability, particularly for soils with initial pH below 7. Likewise, the electrical conductivity values remained within acceptable salinity ranges (0.19-0.88 dS m -1 ) for the majority of the crops (Richards, 1954;Sonmez et al, 2008) water soluble product could be applied with irrigation water, making its distribution in the soil more efficient, particularly on hillsides that are more prone to erosion (Youlton et al, 2006;Norambuena et al, 2014).…”

“…Calcium‐based amendments, such as calcium carbonate (CaCO 3 ), calcium sulfate (CaSO 4 ) or calcium oxide (CaO)/hydroxide [Ca(OH) 2 )], have been shown to improve the stability of soil aggregates, decrease clay dispersion, and reduce runoff and soil loss ( Baldock et al, ; Chan and Heenan , ; Youlton et al, ; Andry et al, ; Norambuena et al, ; Aye et al, ) (Tab. ).…”