Response of soil phosphorus availability, phosphorus uptake and yield to soil bio-stimulant amendments

Galen E. Woodward

In an effort to develop sustainable practices and respond to increased fertilizer costs, soil amendments (SA) such as green and animal manures have increasingly become part of conventional and organic agricultural systems. In addition to these SA, a variety of promising soil bio-stimulant amendments (SBA) has emerged as potential commercially viable options for improving sustainable production. Most SA and several SBA are represented in Columbia Basin (CB) agricultural systems and each varies in use and application rate. Columbia Basin soils often have limited phosphorus (P) availability since many soils are high in calcium carbonate which limits P availability. Soil amendment applications may be used to improve soil nutrient availability and/or uptake. The purpose of this study was to 1) compare different types of SBA to composted manure in relation to their effects on soil P availability, 2) determine whether plant P uptake was improved by SA and SBA applications, and 3) to assess SBA supplements on yield. Three SBAs (Apex 10, Bio Base and leonardite) and composted manure were selected to determine the yields effects in potato (Solanum tuberosum L.), wheat (Triticumaestivum L.) and triticale (Triticale hexaploide L.) production over two consecutive years (2012-2013). Treatments include: an untreated control, composted manure, leonardite, Apex 10 and Bio Base v at rates of 0, 11.2 Mg ha-1 , 224.17 kg ha-1 , 2.35 L ha-1 , 2.35 L ha-1 , respectively. These SBA were applied on two commercial vegetable farms (Pasco and Eltopia) with different soil textures. Potatoes were grown in the first year (2012) at each location while wheat was gown in Pasco and triticale in Eltopia the second year (2013). Soil samples were collected and analyzed for soil P, soil organic matter (SOC) and phosphatase (Ptase). Whole plant samples were collected, separated, and analyzed for dry mass (Dmass), P concentration (Pconc), P content (Pcont), and yield. In conjunction with SBA applications, the research plots were split the second year to compare annual applications with residual effects from a onetime application. Indicators of a soil response to SBA application were significantly different by field and sample time, but few treatment effects were observed. A correlation between soil P, SOC, and Ptase showed an inverse relationship between Ptase and soil P and a direct relationship between Ptase and SOC. The negative correlation between Ptase and soil P may be attributed to a reduced need to convert unavailable to available P by microorganisms. While P partitioning among potato tissues showed no treatment effect there were differences by field and sample time. Tuber yield differed by field, but not by treatment. Conversely, wheat and triticale yields responded to treatments. This suggests that SA and SBA application in previous years may produce a residual response in wheat whereas annual treatments did in triticale.

Response of soil phosphorus availability, phosphorus uptake and yield to soil bio-stimulant amendments

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