Effect of a Newly Developed Pelleted Papermill Biosolids on Crop and Soil

Abstract

The US is one of the leading global producers of paper industry with approximately 24 percent of the share of world paper supply. Despite diversity of the feedstock and production methods, C rich papermill biosolids (PB) is a major byproduct of paper production process. Landfilling is the predominant method of PB management. Increasing landfill cost and its potential environmental consequences have incentivized research and development efforts to find beneficial uses for PB. This sensible option reduces the overall paper production costs and increases environmental sustainability. Pelletization of PB increases its marketability by reducing transportation costs. This greenhouse study was conducted to gain a better understanding of the properties and effects of a recently developed pelletized papermill biosolids (PPB) on bell pepper (Capsicum annuum L.) and soil. Urea and PPB were each applied at four total N rates equivalent to 45, 90, 135, and 180 kg N ha﹣1 and an additional control treatments of 0 N was included. The total C and N concentration in this PPB were 379 and 14 g·kg﹣1 respectively and its C:N ratio was 27.2. Nitrogen treatment significantly (P ≤ 0.0839) influenced pepper height, dry biomass, N concentration, and N uptake. Plant height ranged from 31.2 to 44.4 cm; 135 kg·ha﹣1 urea-N and PPB-N produced the tallest and shortest plants respectively. Dry biomass of the pepper that did not receive any N, those treated with urea-N or PPB-N were 5.3, 5.7 - 7.5, and 5.9 - 6.5 g·plant﹣1 respectively. Nitrogen concentration in control treatment (0 N) was 36.4 g·kg﹣1 and that of pepper treated with any N ranged from 32.0 - 40.7 g·kg﹣1. There was an inverse numerical, albeit not always statistically significant, relationship between PPB rate and plant N concentration. Generally, pepper treated with urea removed significantly more N from soil than control or PPB treated pepper. Nitrogen uptake by plants that did not receive any N and those amended with urea or PPB were 194, 229 - 270, and 155 - 164 mg·plant﹣1 respectively. Pepper N uptake and concentration data indicate that higher rates of PPB resulted in immobilization of native soil and PPB-N due to its wide C:N ratio (27.2). Nitrogen treatment significantly influenced soil pH, SOM, total C and N (P > 0.1). Soil organic matter and total C in post-harvest soil samples were 17.4 - 19.4 and 21.9 - 35.0 g·kg﹣1 respectively. The observed increase in soil total C and SOM highlights the potential beneficial use of PPB as a means to improve soil health and sequester C in soil. Narrowing the C:N ratio of PPB, by coapplication or incorporation of the mineral N into the pellets will make it an attractive organic N fertilizer.