Leaching and reclamation of a biochar and compost amended saline–sodic soil with moderate SAR reclaimed water

Abstract

a b s t r a c tRemediating saline-sodic soils with organic amendments is increasingly seen as a cheaper and sustainable alternative to inorganic materials. The reclamation potential of biochar, biosolids and greenwaste composts applied to a saline-sodic soil was evaluated in a laboratory leaching experiment using moderate SAR reclaimed water. Treatments included biochar, biosolids co-compost, greenwaste compost (all applied at a 75 t ha −1 rate), gypsum (50% soil gypsum requirement), biochar + gypsum, biosolids + gypsum, greenwaste + gypsum and a non-amended control. All treatments were subjected to a one month incubation after which, soils were filled in columns and leached using reclaimed water until 7 PV of water had passed. Cumulative leachate losses of Na + , Ca 2+ , and Mg 2+ were evaluated in addition to soil properties after leaching. Results show that leaching with moderate SAR water was effective in reducing the soil salinity and sodicity of all soils, irrespective of amendment application. However, incorporating biochar and composts significantly enhanced this effect. Salt leaching was higher in soils treated with organic amendments. Cumulative leachate losses of cations were significantly higher from biochar and compost treated soils compared to gypsum and unamended controls. Improvements in soil aggregate stability and saturated hydraulic conductivity were prominent in compost treated soils. After leaching, soil analyses indicated that organic amendments lowered significantly more soil EC e , ESP and SAR than that of the control soils and saturated the exchange complex with Ca 2+ . Soil pH was significantly reduced and CEC was significantly increased in only compost treated soils. Although individual organic amendment applications proved to be significant enough to remediate a saline-sodic soil, combined applications of gypsum and organic amendments were more effective in improving soil properties directly related to sodium removal including sodium leaching, hydraulic conductivity, ESP, and SAR, and therefore could have a supplementary benefit of accelerating the reclamation process.

Rehabilitation of calcareous saline‐sodic soil by means of biochars and acidified biochars

“…The H + from the acidified biochar and Ca 2+ ions from either the dissolution of calcite or the biochar itself helps to replace Na + on soil colloid and finally Na + excluded from the soil (Figure ). This result was in agreement with results of Chaganti et al (), who indicated that using biochar decreased soil Na + concentration. Also, Akhtar, Andersen, and Liu () reported that the application of biochar significantly decreased the Na + concentration of salt‐affected soil.…”

“…Acidification of soil likely induced release of surplus of Ca 2+ , Mg 2+ , and Cl − into leachates. This result is in line with result of Chaganti et al (). However, the concentration of HCO 3 − in leachates of acidified biochar‐treated soils was enhanced gradually, which might be due to dissociation of carbonic acid to HCO 3 − and H + .…”

“…Moreover, all the acidified biochars were more effective than were their corresponding nonmodified biochars in reducing the soil Mg 2+ concentration. Our data were in line with those of Chaganti et al (), who indicated that the use of biochar decreased soil Mg 2+ concentration.…”

Effect of initial soil water content and bulk density on the infiltration and desalination of melting saline ice water in coastal saline soil

“…It is important to note that the soil column experiment in the present study was performed on homogeneous soil and melting temperatures, whereas soil spatial heterogeneity is usual for chemical and physical properties, including water, salt and soil pores, which influence hydraulic conductivity and the rate of infiltration of melting saline ice (Assouline, ; Carvalho, Eduardo, Almeida, Santos, & Sobrinho, ; Dafny & Šimůnek, ). The above factors all further influence the salt leaching effect in saline soil (Chaganti et al, ). Moreover, the different infiltration processes among treatments in the present study suggested changes in soil hydraulic conductivity, which is mainly affected by cation exchange capacity (Mandal et al, ), soil structure (Alrajhi et al, ), aggregate stability (Suarez et al, ), clay dispersion (Moreno et al, ) and so on.…”

“…Elevated values of the sodium adsorption ratio (SAR) of the source water can lead to a reduction in hydraulic conductivity and rate of infiltration (Suarez, Wooda, & Lesch, 2006). In addition to the source water, initial soil properties such as the soil water content and degree of soil porosity, are important factors that influence saline water infiltration (Ahmed et al, 2012;Alrajhi, Beecham, & Hassanli, 2017;Chaganti, Crohn, & Simunek, 2015). Smaller initial soil water content and bulk density favour saline water infiltration and salt leaching from the soil (Chaganti et al, 2015).…”