Soil and Crop Effects of a Subsurface Fluid Lime Applicator

Abstract

Highlights Continuous no-tillage with fertilizer deep-banded below the seed can result in stratified soil acidity that cannot be rapidly addressed with surface-applied lime. We modified a tractor-driven sweep implement to inject fluid lime that targets sub-surface soil acidity with minimal disturbance that maintains surface crop residues, and tested it prior to seeding winter peas at 4 liming rates. Soil chemistry, microbiology, and crop growth were monitored over the season. Abstract. Deep-banding ammonia and urea-based nitrogen fertilizers under continuous no-tillage can result in stratified acidification at the fertilizer-injection depth. Currently, producers address this acidification through primary tillage operations that mix the soil and dilute the acidification, but increase the hazard of soil erosion. Typically, lime is required to ameliorate soil acidity; however, surface-applied lime does not immediately address subsurface acidity, and often tillage is used to incorporate lime and correct acidified layers created through deep-banded fertilizer placement under no-tillage. Here, we designed, developed, and tested a subsurface applicator for fluid lime that can target specific soil depths and rates. The liming system was tested in Eastern Washington on a field that had been under continuous no-tillage for 25 years, had stratified soil acidity, and was to be planted to winter pea, a crop known to be sensitive to acid soil conditions. Soil pH and carbon distribution, microbial changes, biomass, and leaf area index (LAI). Results indicated that the lime targeted the seed zone and raised pH significantly; effects on biomass were marginally significant; and effects on LAI and vegetation cover were insignificant. Topography had a significant effect on all variables due to changes in applicator effectiveness with changes in soil mechanics, meaning as-applied rates varied from desired rates. Keywords: Liming, No-tillage, Precision agriculture, Soil acidity, Soil microbiology.