Effects of Apple Orchard Production Systems on Some Important Soil Physical, Chemical and Biological Quality Parameters

Abstract

ABSTRACT Three different grassed-down apple orchard production systems (organic or biological, BFP; conventional, CFP; and integrated, IFP) in New Zealand were compared for their effects on some important soil physical, chemical and biological quality parameters. A total of 17 grassed-down apple orchards with alley and treeline areas from BFP, CFP and IFP systems in experimental sites and two commercial (organic and conventional) orchards were studied. At each orchard, soils were sampled at three depths (0–50, 50–150, 150–300 mm) in the treeline and alley and were analysed for soil physical properties (soil bulk density, SBD; and soil infiltration rate, IR). Samples from the top two depths (0–50 and 50–150 mm) were also analysed for soil chemical (pH, P, K, Ca, Mg, S) and biological (earthworm number, fresh biomass and composition; microbial biomass C, BC; microbial biomass N, BN; CO, evolution) parameters. Earthworm parameters were determined to a depth of 0.25 m. In general, significantly lower SBD and higher IR occurred in treeline than alley in all orchards due to soil compaction by orchard vehicles in the alley. The BFP treeline and commercial organic orchard showed lowest SBD and highest IR. Soil chemical parameters were found to be related to nutrient management practices imposed such as increased K and S in BFP treelines due to pea straw additions. Returns of mown clippings from alleys to treelines enhanced nutrient transfers and increased nutrient levels in treelines of BFP and IFP orchards. Earthworm number and biomass were sensitive indicators and were high in pea straw-treated treelines of BFP orchards due to substrate additions. Although earthworm biomass varied in the alleys between orchards, high earthworm numbers occurred in most orchard alleys. Highest number of earthworm species were found in BFP and commercial organic orchards. The measured soil respiration (CO2 evolution) showed significant differences between soil depths but no significant differences between orchard systems except in one site where BFP showed higher CO2 evolution than IFP or CFP. The BC and BN were significantly higher in commercial organic than conventional orchards and in topsoils than subsoils in about half of the orchards studied. Overall, sensitive soil quality indicators found, capable of distinguishing between orchard management treatments, were SBD, IR, earthworm number, fresh biomass and composition while those which distinguished between topsoils and subsoils were CO2 evolution, BC and BN.