Pre-Plant Anhydrous Ammonia Placement Consequences on No-Till Versus Conventional-Till Maize Growth and Nitrogen Responses

With the advent of precision guidance systems, maize (Zea mays L.) farmers in various tillage systems have more options in pre-plant nutrient banding relative to the intended crop rows. Anhydrous ammonia (NH3) placement during pre-plant application is of interest because of concerns for possible ammonia toxicity to maize seedlings when high NH3 rates are applied too close to the seed row and the need to improve plant-nitrogen (N) use efficiencies. Field studies were conducted between 2010 and 2012 near West Lafayette, IN, to compare traditional angled (diagonally) vs. precision-guided parallel NH3 applications (the latter was offset 15 cm from the future row) in no-till and conventional tillage systems. The NH3 was injected to depths of about 12 cm at N rates of 145 and 202 kg N ha−1. Maize was planted with additional starter N (20 kg N ha−1) within 6 d of NH3 application. Neither NH3 application placement resulted in significant maize seedling mortality. Conventional tillage increased mean grain yields across N rates and placement treatments from 10.6 to 11.6 Mg ha−1. Tillage did not impact reproductive-stage leaf chlorophyll content (SPAD), or whole-plant N content at maturity when NH3 was parallel applied, but these plant responses were significantly lower in no-till after diagonal application. Lowering the pre-plant N rate to 145 from 202 kg N ha−1 significantly lowered maize whole-plant biomass and N accumulation at maturity with diagonal application, but not when NH3 was parallel applied

Soil depth and geographic distance modulate bacterial β-diversity in deep soil profiles throughout the U.S. Corn Belt

Understanding how microbial communities are shaped across spatial dimensions is of fundamental importance in microbial ecology. However, most studies on soil biogeography have focused on the topsoil microbiome, while the factors driving the subsoil microbiome distribution are largely unknown. Here we used 16S rRNA amplicon sequencing to analyse the factors underlying the bacterial β-diversity along vertical (0–240 cm of soil depth) and horizontal spatial dimensions (~500,000 km2) in the U.S. Corn Belt. With these data we tested whether the horizontal or vertical spatial variation had stronger impacts on the taxonomic (Bray-Curtis) and phylogenetic (weighted Unifrac) β-diversity. Additionally, we assessed whether the distance-decay (horizontal dimension) was greater in the topsoil (0–30 cm) or subsoil (in each 30 cm layer from 30–240 cm) using Mantel tests. The influence of geographic distance versus edaphic variables on the bacterial communities from the different soil layers was also compared. Results indicated that the phylogenetic β-diversity was impacted more by soil depth, while the taxonomic β-diversity changed more between geographic locations. The distance-decay was lower in the topsoil than in all subsoil layers analysed. Moreover, some subsoil layers were influenced more by geographic distance than any edaphic variable, including pH. Although different factors affected the topsoil and subsoil biogeography, niche-based models explained the community assembly of all soil layers. This comprehensive study contributed to elucidating important aspects of soil bacterial biogeography including the major impact of soil depth on the phylogenetic β-diversity, and the greater influence of geographic distance on subsoil than on topsoil bacterial communities in agroecosystems

Crop updates 2006 - Farming Systems

This session covers nineteen papers from different authors: SOIL AND NUTRIENT MANAGEMENT 1. Inve$tigating fertili$er inve$tment, Wayne Pluske, Nutrient Management Systems 2. KASM, the potassium in Agricultural System Model,Bill Bowden and Craig Scanlan, DAWA Northam and UWA, School of Earth and Geographical Sciences 3. Long term productivity and economic benefits of subsurface acidity management from surface and subsurface liming, Stephen Davies, Chris Gazey and Peter Tozer, Department of Agriculture 4. Furrow and ridges to prevent waterlogging, Dr Derk Bakker, Department of Agriculture 5. Nitrous oxide emissions from a cropped soil in Western Australia, Louise Barton1, David Gatter2, Renee Buck1, Daniel Murphy1, Christoph Hinz1and Bill Porter2 1School of Earth and Geographical Sciences, The University of Western Australia, 2Department of Agriculture GROWER DECISIONS 6. Managing the unmanageable, Bill Bowden Department of Agriculture 7. Review of climate model summaries reported in Department of Agriculture’s Season Outlook, Meredith Fairbanks, Department of Agriculture 8. Mapping the frost risk in Western Australia, Nicolyn Short and Ian Foster, Department of Agriculture 9. .35 kg/ha.day and other myths, James Fisher, Doug Abrecht and Mario D’Antuono, Department of Agriculture 10. Gaining with growers – Lessons from a successful alliance of WA Grower Groups, Tracey M. Gianatti, Grower Group Alliance 11. WA Agribusiness Trial Network Roundup – 2005, Paul Carmody, Local Farmer Group Network, UWA 12. Drivers of no-till adoption, Frank D’Emdenabc, Rick Llewellynabdand Michael Burtonb,aCRC Australian Weed Management; bSchool of Agricultural and Resource Economics, UWA. cDepartment of Agriculture, dCSIRO Sustainable Ecosystems, Adelaide PRODUCTION SYSTEMS, PRECISION AGRICULTURE AND SUSTAINABILITY 13. Maintaining wheat and lupin yields using phase pastures and shielded sprayers to manage increasing herbicide resistance, Caroline Peek, Nadine Eva, Chris Carter and Megan Abrahams, Department of Agriculture 14. Analaysis of a wheat-pasture rotation in the 330mm annual rainfall zone using the STEP model, Andrew Blake and Caroline Peek, Department of Agriculture 15. Response to winter drought by wheat on shallow soil with low seeding rate and wide row spacing, Paul Blackwell1, Sylvain Pottier2and Bill Bowden1 1 Department of Agriculture; 2Esitpa (France) 16. How much yield variation do you need to justify zoning inputs? Michael Robertson and Greg Lyle, CSIRO Floreat, Bill Bowden, Department of Agriculture; Lisa Brennan, CSIRO Brisbane 17. Automatic guidance and wheat row position: On-row versus between-row seeding at various rates of banded P fertilisers, Tony J. Vyn1, Simon Teakle2, Peter Norris3and Paul Blackwell4,1Purdue University, USA; 2Landmark; 3Agronomy for Profit; 4 Department of Agriculture 18. Assessing the sustainability of high production systems (Avon Agricultural Systems Project), Jeff Russell and James Fisher, Department of Agriculture, Roy Murray-Prior and Deb Pritchard, Muresk Institute; Mike Collins, ex WANTFA, 19. The application of precision agriculture techniques to assess the effectiveness of raised beds on saline land in WA, Derk Bakker, Greg Hamilton, Rob Hetherington, Andrew Van Burgel and Cliff Spann, Department of Agricultur

Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity

Carbon-sensitive pedotransfer functions for plant available water

Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (θAWHC), while some studies show the ability to substantially increase θAWHC through management. The Soil Health Institute\u27s North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (θFC) and permanent wilting point (θPWP). New pedotransfer functions had predictions of θAWHC that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on θAWHC. For an increase in SOC of 10 g kg–1 (1%) in noncalcareous soils, an average increase in θAWHC of 3.0 mm 100 mm–1 soil (0.03 m3 m–3) on average across all soil texture classes was found. This SOC related increase in θAWHC is about double previous estimates. Calcareous soils had an increase in θAWHC of 1.2 mm 100 mm–1 soil associated with a 10 g kg–1 increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience

Full-Season Retrospectives on Causes of Plant-to-Plant Variability in Maize Grain Yield Response to Nitrogen and Tillage

Maize (Zea mays L.) plant-to-plant variability at different plant densities and N fertilizer rates has been studied previously, but little attention has been devoted to consequences of different N placement and tillage management on plant variability in kernel number (KN) and grain yield. This study investigated effects of pre-plant N placement relative to intended maize rows on the origin and magnitude of plant-to-plant variability in per-plant grain weights (GW). Field studies compared two “shallow” anhydrous ammonia (NH3) placement directions (diagonal to future row vs. parallel but 15-cm offset from the row) in both no-till and conventional tillage systems at two N rates (145 and 202 kg N ha−1). Maize was planted with starter fertilizer (20 kg N ha−1) within 6 d following NH3 application. Aboveground growth and development was monitored on bar-coded plants from seedling emergence to maturity. Plant-to-plant uniformity in GW and KN was not improved by parallel NH3 placement, conventional tillage, or a higher N rate; however, all three factors resulted in a slight shift towards higher mean GW and KN. Within-row plant spacing and relative seedling emergence time had little influence on relative GW. Within-row differences in silk emergence timing and estimated stem volumes were the most highly correlated parameters to per-plant GW. Regression models confirmed that either of these mid-silking factors explained \u3e50% of such GW variations within most treatment combinations. Even in management systems with conventional tillage and precision N fertilizer placements, precision seed placement alone will not guarantee low variability in per-plant GW

Post-silking Factor Consequences for N Efficiency Changes Over 38 Years of Commercial Maize Hybrids

Hybrid selection in maize (Zea mays L.) over the decades has increased post-silking dry matter (PostDM) and nitrogen (PostN) accumulation, often with an accompanying increase in one or more N use efficiency (NUE) metrics such as partial factor productivity (PFP), N conversion efficiency (NCE), and N internal efficiency (NIE). More certainty on the underlying mechanisms of how PostDM and PostN changes over time have contributed to NUE gains or losses in modern-era hybrids can only be realized by directly comparing hybrids of different eras in the context of production-system-relevant management systems. A two-year and two-location field study was conducted in Indiana with two N rates (55 and 220 kg N ha−1), three plant densities (54,000, 79,000, and 104,000 plants ha−1) and eight commercial hybrids that were released by a single seed company from 1967 to 2005. The main treatment effects of N rate, density, and hybrid dominated the PostDM and PostN responses, and there were no significant two-way or three-way interactions. Total dry matter at maturity gains averaged 80 kg ha−1 year−1 of hybrid release when averaged over locations, plant densities and N rates. Total N contents at maturity increased 0.68 kg ha−1 year−1, primarily due to annual increases in grain N content (0.8 kg ha−1 year−1). Post-silking N uptake rate increased 0.44 kg ha−1 year−1 for these era hybrids in more favorable production site-years. Slopes of grain N concentration increases per unit PostN gain were similar for all hybrids. Gains in average PFP over time were considerably higher at the low N rate (0.9 kg ha−1 year−1) than at the high N rate (0.3 kg kg−1 year−1). Hybrid gains in NIE were evident from 1967 to 1994, but not thereafter. The low N rate and higher plant densities also increased relative NIE and NCE values, but without hybrid interactions. There was no consistent trend of NIE or NCE gains in these hybrids primarily because grain and whole-plant N concentrations didn't decline over the decades at either N rate, and because NIE and NCE were often plant-density dependent

Relationships Between Ear-Leaf Nutrient Concentrations at Silking and Corn Biomass and Grain Yields at Maturity

Ear-leaf nutrient concentrations at silking correlated strongly with corn grain yield. Ear-leaf nutrient concentrations at silking correlated strongly with whole-plant biomass. Ear-leaf N, P, S, Cu, and Fe concentrations explained most of the grain yield variation. State recommendations for certain minimum nutrient concentrations may need adjustment. Historically, corn (Zea mays L.) ear-leaf N concentrations at mid-silking have been positively correlated with grain yield (GY). Many state and regional fertilizer recommendations provide “nutrient sufficiency ranges” or threshold nutrient concentrations for N and other nutrients in ear leaves sampled at silk emergence, but these are based on studies conducted decades ago with much lower yielding hybrids grown at lower plant densities. In response to this potential knowledge gap, we collected corn ear-leaf samples at mid-silking in field studies conducted near West Lafayette, IN, from 2010 to 2016. These field studies involved comparisons of multiple hybrids, plant densities or tillage systems for their response to nutrient management alternatives (e.g., macronutrient rates, placement, and timing). The ear-leaf samples were analyzed for nutrient concentrations (N, P, K, Ca, Mg, S, Zn, Mn, Fe, Cu, B, and Al), and each plot\u27s nutrient concentration data were subjected to regression analysis to evaluate their relationship with plot level dry matter (DM) accumulation and GY responses. Variation in ear-leaf N, P, S, and Cu concentrations explained \u3e50%, while Fe explained \u3e40%, of the variation in both GY and DM. These nutrients (N, P, S, Cu, and Fe) were also positively correlated with each other (Pearson r ranged from 0.46–0.89). However, ratios of ear-leaf nutrient concentrations at silking consistently explained less of the GY variation than single nutrient concentrations. The overall relationships of ear-leaf nutrient concentrations with GY suggests revisions in state recommendations for ear-leaf “nutrient sufficiency” may be warranted for some nutrients

Understanding Global and Historical Nutrient Use Efficiencies for Closing Maize Yield Gaps

ABSTRACT Global food security must address the dual challenges of closing yield gaps (i.e., actual vs. potential yield) while improving environmental sustainability. Nutrient balance is essential for achieving global food security. Historical (in distinct "Eras" from late 1800s to 2012) and geographical (in United States vs. remainder of World) changes in maize (Zea mays L.) grain yields and plant nutrient content (N, P, and K) were characterized from studies (>150) with known plant densities. At the community scale, greater yield to nutrient content ratios (physiological efficiency, PE) were documented for United States vs. World. The U.S. historical trend displayed increasing gains for community-scale yield and nutrient uptake, except for a recent decline attributed to weather. At the individual-plant scale, geographic PE differences over time were primarily explained by changes in yield, and secondarily by nutrient content changes. Despite wide variation, high-yield maize in both geographies was associated with balanced N/P (5:1) and N/K (1:1) ratios. More scope exists for maize nutrient PE gains in developing regions. Achieving balanced nutrition in optimally integrated soil-crop management cropping systems will facilitate simultaneous realization of high-yield and bio-fortification goals in maize improvement efforts

Per-plant eco-physiological responses of maize to varied nitrogen availability at low and high plant densities

Although maize (Zea mays L.) routinely experiences both intra- and inter-specific competition for limited resources, most plant-plant interaction studies have principally focused on maize-weed interactions. Thus very few investigations have considered the impacts of plant crowding and nitrogen (N) availability on maize intra-specific competition. The primary objective of this two-year field study near West Lafayette, IN was to investigate the per-plant eco-physiological responses of modern maize genotypes to varied N availability (0, 165, and 330 kg side-dress N ha-1) at low and high plant densities (54,000 and 104,000 plants ha-1, respectively) by measuring responses among dominated [lowermost 25% per-plant grain yield (GYP)], intermediate, and dominant (uppermost 25% GYP) individual plants in each treatment combination. Parameters measured at the per-plant level included R1 green leaf area (LAP), R1 SPAD, anthesis-silking interval (ASIP), GYP, R6 total aboveground biomass (TBP), and harvest index (HIP). In both years, severe intra-specific competition for soil N in the highly crowded, low-N environment resulted in low R1 LAP and SPAD values, high ASIP values, and reduced GYP, R6 TBP, and HIP values, particularly among dominated plants. Intense competition in this environment also led to (i) high dominant group/dominated group mean ratios for most parameters; (ii) high plant-to-plant variability for R1 SPAD, ASIP, GYP, and HIP; and (iii) high frequencies of barren and low-yielding plants. Insufficient N at high plant densities thus encouraged the formation of plant hierarchies composed of markedly dominated individuals with diminished source capability and severely impaired biomass partitioning to developing grain