Groundcover Management and Nutrient Source Effects on Soil Carbon and Nitrogen Sequestration in an Organically Managed Apple Orchard in the Ozark Highlands

Abstract

<jats:p>Orchards established on weathered, acidic mineral soils in the Ozark Highlands must be managed to meet tree nutritional requirements. However, a common characteristic of Ozark Highland soils is a relatively low soil organic matter (SOM) concentration, a condition that can have detrimental effects on orchard productivity. Organic orchard management poses specific challenges to managing competitive under-tree vegetation and supplying appropriate supplemental nutrition to maintain tree growth and cropping. In Mar. 2006, an experimental apple orchard was established to evaluate the effects of under tree, in-row groundcover management system (i.e., shredded paper, wood chips, municipal green compost, and mow-blow), and nutrient source (i.e., non-fertilized control, composted poultry litter, and pelletized organic commercial fertilizer) on SOM, carbon (C), and nitrogen (N) concentration, and soil C and N sequestration over time in an organically managed orchard in the Ozark Highlands region of northwest Arkansas. Soil organic matter, total C, and total N concentrations (soil weight basis) and contents (area basis) in the top 7.5 cm increased in all groundcover management systems from 2006 to 2011. The greatest differences were observed with municipal green compost treatments. Significant interactions between groundcover management treatment and nutrient source were only observed for SOM concentration, whereas nutrient source did not affect total C and total N concentrations or contents. Soil C sequestration rates were 0.9, 1.0, and 2.8 Mg·ha<jats:sup>−1</jats:sup> per year under the shredded paper, wood chip, and green compost treatments, respectively, whereas total C content did not change over time under the mow-blow treatment. The green compost treatment was the only treatment that had significant total N sequestration occur (0.25 Mg nitrogen/ha/year). Results of this study indicate that organic cultural methods can significantly augment near-surface soil C and N contents, which will likely increase productivity, of apple orchards in the Ozark Highlands over a relatively short period time after establishment. This study has implications for orchards in similar soils or environmental circumstance and for both organic and conventional management systems.</jats:p>

Groundcover Management System and Nutrient Source Impacts on Soil Quality Indicators in an Organically Managed Apple (Malus ×domestica Borkh.) Orchard in the Ozark Highlands

“…Previously, we have reported that SOM in the top 10 cm increased over time in all GMS with the largest increase occurring in the green compost treatment (Mays et al, 2014). Furthermore, despite initial uniformity in 2006 before planting where SOM concentration averaged 1.5% across all treatments, by 2012, SOM concentration differed among nutrient sources within GMS (Mays et al, 2014).…”

“…Soil organic matter has often used as a soil quality indicator (Fliebach et al, 2006;Granatstein and Mullinix, 2008;Gregorich et al, 1994;Karlen et al, 1992;Loveland and Webb, 2003;Merwin et al, 1994Merwin et al, , 1995, and changes in SOM have been linked to changes in other soil properties and processes. The near-surface SOM, total C, and total nitrogen (N) concentrations and contents, C:N ratios, and BD did not differ (P > 0.05) among GMS-nutrient source treatment combinations at the initiation of the study (Mays, 2013) indicating that soil conditions were as uniform throughout the study area as could reasonably be expected at the time of organic orchard establishment. Therefore, it was reasonably assumed that differences observed among treatments over the subsequent years were the result of the treatments rather than inherent differences.…”

“…The experimental organic orchard site had been in horticultural crop production for 75 years. Before orchard establishment, the site was prepared and cultivated in 2005 (described in Mays et al, 2014). Using soil test results, soil pH was adjusted with agricultural lime and 5 t · ha -1 of composted manure was applied to prepare the planting beds.…”

“…The commercial fertilizer used from the initiation of the study through the 2011 application was certified organic material from poultry manure (Perdue AgriRecycle, Seaford, DE; 4N-2P-3K analysis; Mays, 2013). The originally selected commercial fertilizer production was subsequently discontinued and an alfalfa-based commercial organic product (Bradfield Organics, Feed Solutions, St. Louis, MO; 3N-1P-5K analysis; Mays, 2013) was applied beginning in 2012. The composted poultry litter was obtained from a local source (Mays, 2013).…”

“…The originally selected commercial fertilizer production was subsequently discontinued and an alfalfa-based commercial organic product (Bradfield Organics, Feed Solutions, St. Louis, MO; 3N-1P-5K analysis; Mays, 2013) was applied beginning in 2012. The composted poultry litter was obtained from a local source (Mays, 2013). The only nutrition the non-fertilized control treatments received came from the GMS treatments.…”