PROBLEM

1. Effects of Biosolids Types on Nitrogen Availability under Varying Tillage Practices Jinling Li (jinling@vt.edu), Gregory K. Evanylo and Xunzhong Zhang, Department of Crop and Soil Environmental Sciences, Virginia Tech • PROBLEM • Reduced tillage on biosolids-amended land decreases runoff and erosion and increases infiltration and soil moisture. Little research has been conducted, however, on the effects of no-tillage on crop response nitrogen availability where biosolids were applied. • INTRODUCTION • Biosolids plant-available nitrogen (PAN) is composed of ammonium N and organic N. Insufficient PAN supply can reduce crop yield, while surplus PAN can lead to soil nitrate N leaching issues. • Biosolids are traditionally incorporated into soil to prevent odors. Tillage increases organic N mineralization; no-tillage increases ammonia volatilization and also reduces risk of erosion and runoff. • OBJECTIVE • To compare the interactive effects of land-applied biosolids types and tillage practices on corn nitrogen availability in Coastal Plain agricultural soils. • METHODS • In 2009 and 2010, two study sites planted with corn (Zea mays L.) were laid out separately on an Orangeburg loamy sand (Fine-loamy, kaolinitic, thermic Typic Kandiudults), in Sussex County, VA. • Experimental design: Split-Plot Design • Main plot treatments: conventional tillage (CT) and no-tillage (NT). • Sub-plot treatments: commercial fertilizers(0x, 0.5x, 1x, 1.5x agronomic N rate*), • anaerobically digested biosolids (AD) and lime stabilized biosolids(LS) (1x N rate). • Each treatment was replicated 4 times. • *1x agronomic N rate= 120 kg ha-1 (2009) & 157 kg ha-1 (2010) • Sampling and analysis: • Pre-Sidedress Nitrate Test (PSNT) • Corn Ear Leaf total Kjeldahl Nitrogen (ELN) • Corn grain yield • End-of-season Corn Nitrate Test (CSNT) • End-of-season soil organic C and total N Lime Stabilized Biosolids Anaerobically Digested Biosolids Biosolids Application PSNT In 2009, both biosolids maintained higher level of NO3 than fertilizers. AD was higher than LS. In 2010, both biosolids maintained lower level of NO3 than fertilizers. AD was lower than LS. In 2009, NO3 level was higher in CT than in NT. All treatments in no-till had values below 450 ppm. Both biosolids maintained low levels of NO3, indicating that biosolids N availability was not excessive and was under control. In 2010, all treatments had values above 450 ppm; LS had value over 2000 ppm. In this situation, much nitrate-N accumulated at the bottom of stalks and could not be utilized by plants. AD was lower than LS. Grain Yield Grain Yield Ear Leaf TKN Soil C & N Analysis CSNT Tillage effects on soil C and N Fertility effects on soil C and N In 2009, both biosolids maintained higher ear leaf N than fertilizers. LS was higher than AD. In 2010, both biosolids maintained lower ear leaf N than fertilizers. LS was higher than AD. • RESULTS AND DISCUSSION • In 2009, due to frequent and sufficient rainfall events, moisture was not a limiting factor. Plants could take up enough N for growth and biosolids maintained higher N levels than fertilizers. • In 2010, hot and dry weather reduced organic N mineralization and increased ammonia volatilization rates. Plant uptake N decreased relatively and biosolids showed lower N levels than commercial fertilizer treatments. In 2009, both tillage and fertility treatment significantly influenced end-of-season soil C and N. Soil organic C and total N were higher in NT than in CT, and AD was higher than LS. Biosolids could sequester more organic C and N. In 2009, both biosolids maintained higher grain yields than fertilizers. LS was higher than AD. Grain yield in 2010 was lower than in 2009. Both biosolids maintained higher yields than fertilizers. • CONCLUSION AND PERSPECTIVE • Both biosolids types maintained higher N availability than commercial fertilizers at 1x N rate. The differences between LS and AD biosolids were possibly due to the varying proportions of inorganic N and organic N. • Biosolids N availability could be influenced by tillage practices, as no-till apparently slowed down the mineralization of biosolids organic N, and incorporation of biosolids into soil could reduce ammonia volatilization. • Biosolids types did not show much organic C sequestration over the first growing season. The evident increasing of biosolids C sequestration would possibly be indicated by the future three-year studies. Properties of land-applied biosolids in 2009 and 2010.