Using Seaweed as a Soil Amendment: Effects on Soil Quality and Yield of Sweet Corn (Zea mays L.)

Abstract

Application of seaweed to manage soil fertility is a traditional practice in many coastal regions, utilizing an inexpensive, abundant, and nutrient-rich resource. As a practice that re-purposes waste materials, diversifies inputs, and relies on coastal resources, seaweed amendment may be an effective and inexpensive means of strengthening and supporting agriculture in coastal agroecosystems. Putatively, seaweed biomass may be a useful amendment for crop production and soil quality improvement due to provision of plant nutrients (e.g. N, P, K, Ca), and promotion of microbial activity, among other benefits. However, limitations of seaweed application include high sulfur (S), salt, and heavy metal content. The objectives of this study were to: (1) evaluate the effects of seaweed biomass application on soil physical, biological, and chemical properties important for agricultural productivity, maintenance of soil quality, and conservation of soil resources; (2) determine the sweet corn (Zea mays L.) yield obtained by implementing seaweed amendment as a soil fertility management practice; and (3) assess the economic feasibility of seaweed amendment for sustainable agriculture through synthesis of experimental findings and cost-benefit comparison between seaweed application and pre-formulated fertilizer use. Low-dose seaweed (LDS), high-dose seaweed (HDS), and pre-formulated 8-1-9 (N-P-K) organic fertilizer (PFF) fertilizer treatments were employed in a sweet corn production field experiment from October 2011 to November 2012. Pre-seeding N application rates were 42, 84, and 45 kg total N/ha for LDS, HDS, and PFF, respectively. All fertilizer treatments received side-dress N at a rate of 68 kg total N/ha. Seaweed was collected and applied in November 2011 and May 2012, and was analyzed for carbon (C), nitrogen (N), heavy metal, and nutrient (e.g. K) content. To determine seaweed effects on soil quality, soil properties were assessed prior to seaweed application (October 2011), and repeatedly throughout the 2012 sweet corn growing season. Soil properties evaluated were aggregate stability, bulk density, infiltration, available water capacity (AWC), nitrate (NO3-), phosphate (PO43-), extractable potassium (K+), extractable calcium (Ca2+), heavy metals (Pb, Cd, Cr, Zn, and As), total K, Fe, Mn, and Ca, electrical conductivity (EC), pH, sulfate (SO42-), soil organic matter (SOM), active C, potentially mineralizable N (PMN), and earthworm abundance. Soil properties were determined using recommended national and regional protocols. To assess the effects of seaweed amendment on crop production, the yield and quality of sweet corn was determined by measurement of yield (hundredweight/ha and bushels/ha), above-ground biomass, average ear weight, and dissolved soluble solids (DSS) content.