The residual effect of Recycled Residual Paper Pulp (RRPP) applications on the yield of lettuce crop, grown in two diverse soil and climate conditions

Abstract

This study evaluates the annual residua or left-overl effect of recycled residual paper pulp (RRPP) used as a soil amending material, on the yield and other agronomic characteristics of lettuce (Lactuca Sativa L.) as well as on major soil properties affecting crop growth and yield. The effect of RRPP was evaluated for the past three years, in two diverse soils (clay loam and sandy loam) and climate conditions. The first and second year the RRPP material was applied in four application rates (0, 1, 2 and 4% by volume) in the top soil surface (0-15 cm), while during the third year of this study, the RRPP material was not applied on the soil. Therefore the main objective of this study is to evaluate the "left-over" or "residual" impact of this material one year after the last application, in contrast to the previous two years where the additive effect was evaluated. The plants were managed using minimum inputs under the LISA (Low Input Sustainable Agriculture) system. RRPP material is a waste product from a major cardboard manufacturing company in Greece. Soil properties measured included bulk density, organic carbon (SOC), pH, electrical conductivity, and volumetrie water content The results indicated a statistically significant increase in SOC for the 4% v/v RRPP application rate in both soils. In general, lettuce yield increase to residual RRPP material was proportional to application rates. The results of this study can be used to support the effectiveness and the duration of RRPP as an alternative and excellent soil improving material in sustainable crop production.