TY - JOUR

T1 - Clay and biochar amendments decreased inorganic but not dissolved organic nitrogen leaching in soil

AU - Dempster, Daniel N.

AU - Jones, Davey L.

AU - Murphy, Daniel V.

PY - 2012/5/25

Y1 - 2012/5/25

N2 - Nitrogen (N) leaching from coarse-textured soils frequently leads to productivity losses and negative environmental consequences. Historically, clay amendment has been used on coarse-textured soils to decrease water repellence and nutrient leaching. More recently, biochar has been proposed as an alternative soil amendment to decrease N leaching while simultaneously storing carbon. As biochar has a greater nutrient-retention capacity, we hypothesised that biochar derived from Eucalyptus marginata would be a more effective amendment than clay at minimising N leaching. The soil used was a coarse-textured agricultural sand with the following treatments: (1) biochar incorporated homogenously into the 0–10 cm soil layer, (2) clay incorporated similarly, (3) biochar added as a layer at 10 cm depth, (4) clay added similarly, or (5) a control. Amendments were added at 25 t/ha and watered periodically over 21 days and watered with the equivalent to 30 mm. Clay and biochar amendments significantly decreased cumulative NH4+ leaching by ~20% and NO3– leaching by 25%. Biochar decreased NO3– leaching significantly more than clay, possibly due to decreased nitrification. Dissolved organic N leaching was not influenced by any treatment. Leaching of N was unaffected by amendment application method. We conclude that to decrease N leaching, land managers should apply the most readily available of the amendments in the most convenient manner.

AB - Nitrogen (N) leaching from coarse-textured soils frequently leads to productivity losses and negative environmental consequences. Historically, clay amendment has been used on coarse-textured soils to decrease water repellence and nutrient leaching. More recently, biochar has been proposed as an alternative soil amendment to decrease N leaching while simultaneously storing carbon. As biochar has a greater nutrient-retention capacity, we hypothesised that biochar derived from Eucalyptus marginata would be a more effective amendment than clay at minimising N leaching. The soil used was a coarse-textured agricultural sand with the following treatments: (1) biochar incorporated homogenously into the 0–10 cm soil layer, (2) clay incorporated similarly, (3) biochar added as a layer at 10 cm depth, (4) clay added similarly, or (5) a control. Amendments were added at 25 t/ha and watered periodically over 21 days and watered with the equivalent to 30 mm. Clay and biochar amendments significantly decreased cumulative NH4+ leaching by ~20% and NO3– leaching by 25%. Biochar decreased NO3– leaching significantly more than clay, possibly due to decreased nitrification. Dissolved organic N leaching was not influenced by any treatment. Leaching of N was unaffected by amendment application method. We conclude that to decrease N leaching, land managers should apply the most readily available of the amendments in the most convenient manner.

KW - black carbon

KW - charcoal

KW - dissolved organic nitrogen

KW - DON

KW - mineralisation

U2 - 10.1071/SR11316

DO - 10.1071/SR11316

M3 - Article

VL - 50

SP - 216

EP - 221

JO - Soil & Tillage Research

JF - Soil & Tillage Research

SN - 1838-675X

IS - 3

ER -