Influence of compost on the physical properties and organic matter fractions of a fine sandy loam throughout the cycle of a potato rotation

Abstract

Potato (Solanum tuberosum L.) rotations often require organic amendments to maintain or improve soil organic matter levels and soil physical properties. However, beneficial effects of compost can be modified by time of application and rotating tillage depth and intensity. This study was conducted to evaluate the effect of compost applied once at different phases in a 3-yr potato, barley (Hordeum vulgare L.), and red clover (Trifolium pretense L.) rotation on a range of soil physical properties and organic matter fractions for a Charlottetown fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island. Soil samples (0–8 cm) were obtained during the second cycle of the rotation (after two compost applications) in the fifth year of the experiment. Soil properties were influenced by compost addition, time of compost addition, and crop phase. Compost-induced benefits in soil physical properties (bulk density, macro-porosity, oxygen diffusion rate, shear vane strength, water-filled pore space) were mainly expressed in the red clover phase of the rotation, where soil density was relatively high compared to the barley and potato phases, due to the absence of tillage. The soil physical parameters, however, were mainly within their established optimum ranges for this soil type. Soil water content at −0.033 MPa was increased by compost in the potato phase, compared to the control. Soil organic matter was influenced by both compost and crop C inputs. Compost increased soil particulate organic matter (POM) in the potato and barley phases. Due to differences in crop residue inputs, compost-related differences in organic matter were minimized in the red clover phase of the rotation. Compost addition increased potato tuber yield above the maximum yield obtained with nitrogen application. This “non-nitrogen” compost yield effect may be related to the slight, but significant, improvement in soil water-holding capacity. Overall , compost application in an intensive 3-yr potato rotation provided benefits for potato productivity and in both soil physical and biological properties. Key words: Soil organic carbon, particulate organic matter, soil physical properties, compost amendment, potato yield, eastern Canada