Benefits and tradeoffs of reduced tillage and manure application methods in a Zea mays silage system.

Kyle M. Dittmer,Heather M. Darby,Tyler R. Goeschel,E. Carol Adair

doi:10.1002/jeq2.20125

Abstract

A critical question is whether there are agricultural management practices that can attain the multiple management goals of increasing yields, preventing nutrient losses, and suppressing greenhouse gas (GHG) emissions. No-till and manure application methods, such as manure injection, can enhance nutrient retention, but both may also enhance emissions of nitrous oxide (N2 O), a powerful GHG. We assessed differences in soil N2 O and carbon dioxide (CO2 ) emissions, nitrate and ammonium retention, and crop yield and protein content under combinations of vertical-till, no-till, manure injection, and manure broadcast without incorporation in a corn (Zea mays L.) silage system. During the growing seasons of 2015-2017, GHG emissions and soil mineral nitrogen (N) were measured every other week or more frequently after management events. Crop yield and protein content were measured annually at harvest. No-till reduced CO2 emissions but had no impact on N2 O emissions relative to vertical-till. Manure injection increased N2 O and CO2 emissions, with the magnitude of this effect being greatest for 1 mo post-application. Manure injection also increased soil ammonium and nitrate but did not increase yield or crop quality relative to broadcast application. Similarly, tillage did not affect crop yield or protein content. Despite the tradeoffs between mineral N retention and elevated GHG emissions, manure injection in no-till systems benefits farmers by reducing soil carbon losses as CO2 , retaining mineral N, and maintaining crop yields and quality.

Highlights

Under traditional agricultural management, pressure to feed a growing population may degrade soils, exacerbate nutrient pollution, and enhance greenhouse gas (GHG) emissions by increasing fertilizer inputs and cultivation (Foley et al, 2011)
Across the maximum range of values for each variable measured within a day, increasing carbon dioxide (CO2), soil moisture, and available NH4+ increased nitrous oxide (N2O) emissions by 109.2, 118.7, and 12.3 g N2O-N ha-1 d-1, respectively (Table S5)
Our findings highlight the tradeoff between mineral N retention and elevated N2O emissions with manure injection

Summary

Introduction

Pressure to feed a growing population may degrade soils, exacerbate nutrient pollution, and enhance greenhouse gas (GHG) emissions by increasing fertilizer inputs and cultivation (Foley et al, 2011). Given the potential for agricultural soils to be nutrient and GHG sources, many best management practices (BMPs) aim to retain nutrients and prevent transport into the atmosphere and surface or groundwater (Liu et al, 2017; Logan, 1993). Because GHG emissions and the fate of carbon (C) and nitrogen (N) within agricultural soils depend on soil and fertilizer management (Duncan et al, 2017; Flach et al, 1997; Lognoul et al, 2017; Plaza-Bonilla et al, 2014; Wang and Dalal, 2015; Webb et al, 2010), BMPs can be designed to retain added nutrients and reduce GHG emissions (Mangalassery et al, 2014; Ruidisch et al, 2013). Soil CO2 flux, a combination of microbial and root respiration (Oertel et al, 2016), increases with temperature (Lloyd and Taylor, 1994) and C availability (Hungate et al, 1997)

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