This project will generate needed information to evaluate opportunities and challenges to soybean production under drained and undrained conditions when different tillage and crop residue management conditions are used. We will be able to better understand soil N availability and the effects of the various management variables being tested on soil health and productivity. Ultimately, this project will allow us to refine soybean management practices (or at least provide a first step) to tailor them to specific soil or cropping management conditions. Currently, very limited information is available on how the variables being considered in this study, which are commonly found throughout Minnesota, impact N availability and crop and soil productivity.
Further, Drs. Naeve and Fernandez have extensive experience in communicating research in effective ways to Extension clientele. Crop producers and other professionals benefit by having the latest research information in formats that are clear, concise, and actionable. Results from research outlined
in this proposal can be communicated to crop producers and ag professionals quickly and effectively by dedicated communications professionals as outlined in the proposal.
With the recent publication of results summarizing effects of drainage on optimal N rates on corn, there is tremendous interest in this site and the research we are conducting there. We plan to hold at least one field day in the summer of 2022, and will certainly be speaking of this work at various field days and events throughout 2022.
The study will be conducted in a long-term research site established on a farmer's field near Wells in south-central Minnesota.
Drainage conditions were established in 2011 with every plot having subsurface tile drains installed. The site was divided into eight blocks where four blocks were randomly assigned to be drained (control drainage structures fully open) and four were randomly assigned to be undrained (control drainage structures completely closed). Each of these blocks was subdivided to accommodate both corn and soybean crops that rotate every year. In 2017, three tillage treatments were imposed: 1) conventional,
2) strip-till, and 3) no-till. Starting in fall 2021 three levels of residue management were added: 1) corn residue removed, 2) cover crop planted in the fall and terminated in spring, and 3) traditional (residue left on the field). Within each of these levels there are five 10x30 ft plots that receive 0, 130, or 260 lbs N/ac during the corn phase and the following year during the soybean phase they receive no nitrogen. The N rates in corn were selected to establish soil N supply (0N) and calculate N use efficiency for the 130N [near the economic optimum N rate (EONR)] and 2x the EONR (260N). The remaining two plots receive 130 lbs N/ac during the corn phase
This treatment structure allows us to share one ‘control’ treatment (130 lbs N on corn) and no treatment on soybean. Therefore, this allows for two additional soybean treatments to compare with the control. We are primarily interested in treatments that interact with drainage, tillage, and residue. We plan to examine the effects of seed treatments and seeding rate across these multiple factors.
Corn Trt Soybean Trt Seed Treatment Population
130 lb 1 None 125k
130 lb 2 Yes 140k
130 lb 3 None 140k
Each of these 5 treatments is replicated within each of 3 residue, 3 tillage, and 2 drainage levels. Thus, the study has 360 10x30 ft plots in corn and 360 plots in soybean for a total of 720 plots. Below is depicted an outline of one block. Multiplied by two crops, two drainage levels, and four replications, there are 16 such blocks in this experiment.
Cover variable
A) Cover crop
B) Residue removed (only forcorn residue)
C) Standard practice (no residue management)
Tillage variable
Individual trts
Conventional Strip-till
No-till
Corn (lbs N/ac) Soy seed trt Soy pop
This proposal will only focus on the soybean plots and will only focus on some measurements. The proposal submitted to AFREC will focus on the corn plots and direct nitrogen effects on corn that are not part of this proposal. However, because all the treatments are followed by soybean and their residual effect will be measured in the soybean plots we will discuss the overall site management in this proposal.
Every fall after harvest, tillage and residue management treatments will be established. In the spring, the plots with cover crop will be chemically terminated. Corn plots will receive the N rate treatments before corn is planted. Next, the study will be planted using corn hybrids and soybean varieties and planting densities best suited to maximize productivity.
Blanket fertilizer treatments (other than nitrogen) will be made in the spring to balance any uneven fertility at the site from prior cycles of experiments. Soil monitoring sensors will be placed in all combinations of drainage and tillage to monitor spring warm up as soon as the frost leaves. Bulk corn will be planted across the site as early as possible utilizing the existing crop and tillage rotations.
Soybean plots will be planted with a small plot planter to establish defined soybean treatments within each drainage x tillage x residue block.
A thorough analysis of soil temperature and moisture at the seed depth will be initiated at planting and continue through emergence. Exact emergence dates and early season crop growth will be analyzed relative to soil and atmospheric data. Today, information about corn and soybean emergence relative to soil temperature and moisture profiles under different drainage and tillage conditions is woefully lacking. The treatments at this site provide an invaluable resource for generating this important resource.
Soil temperature and moisture profiles to 2’ depths will continue through the season. These data will be critically important for a better overall understanding of tillage and drainage effects on soil moisture levels. These data are critically important in connecting the dots between drainage, tillage, and yield effects. This will allow us to explain differences in yield responses to tillage and drainage across years.
Along with soil physical properties, we will examine nitrogen availability and mineralization profiles throughout the season. Corn and soybean plots will be maintained throughout the summer and plants will be harvested for yield and analyzed for seed quality at maturity.
As outlined in Goal 4, we will continue to fully characterize the site for soil physical, chemical, and biological chrematistics derived from the long-term effects of drainage and tillage on Minnesota soils productivity. Crop development and its ability to obtain water and nutrients can be impacted by how well the root system explores the soil volume. The three main variables proposed in this project (Drainage, Tillage, and Residue) have a direct effect on soil bulk density, water infiltration, and crop-root penetration and soil volume exploration. Similarly, soil carbon and nitrogen pools along with microbial communities are in a delicate balance that can be profoundly altered by our management. The long- term history of this study site provides a truly unique setting to investigate how the interaction of the main management variables already mentioned influence soil functions and ultimately soybean yield.
During the establishment phase in which residue management will be added to the long-term drainage and tillage variables, we will collect soil samples to establish a baseline of soil carbon and nitrogen pools and soil microbial community structure. This baseline is critically important to evaluate the impact of management over time. Soil carbon and nitrogen pools (organic, inorganic, and total) will be measured by chemical analysis and microbial communities by soil phospholipid fatty acid analysis (PLFA).