Goal 1: Assess the capacity of nurse crops to hold N and protect soil from eroding prior to potato hilling.
Objective 1- determine optimum nurse crop species and planting rate to obtain optimum efficiency.
Objective 2- assess optimum method and timing of nurse crop destruction.
Goal 2: Assess the effects of alternative methods to cover cropping and primary tillage timing on small grain yields, potato yields, and production efficiency.
Objective 3- determine most effective and efficient methods for fall cover and primary tillage preceding a potato crop using either underseeding or cover cropping.
Objective 4- assess economic feasibility of cover crop and tillage methods.
Nurse Crop Trials
We will establish nurse crop trials at the two University of Maine Experiment Station farms (Orono, ME and Presque Isle, ME). We will evaluate seeding rate, seed type, and destruction dates and methods of the nurse crop in two replicated trials. Cereal rye and spring oats will be used as the nurse crops with seeding rates of 100 or 200 lbs of rye or oats per acre. Nurse crop destruction methods of herbicide, hilling/cultivation, and herbicide plus hilling will be compared. We will grow round white potatoes at the Orono location and Russet Burbank potatoes for the Aroostook county location. Each of those varieties are typical for the area. Plot areas will be established, seed spread by hand and incorporated with a tine cultivator. Then plots will be marked and hand planted. Seed will be covered with planter discs.
At approximately 21 to 24 days after planting (6”-8” potato plant height), above and below-ground nurse crop biomass will be collected by plot (two 2-ft2 samples per plot) to assess production prior to destruction. A separate strip of plots will be sampled and destroyed at 30 days after planting. We will collect soil samples for nutrient analysis and nurse crop N status will be assessed by NDVI prior to killing, and potato crop N status will be assessed at 4 and 8 weeks after hilling.
Yield samples will be taken a month following top-kill. Potatoes will be graded to US number 1 and total yield. Ten potatoes will be sampled for skin quality and internal defect. Experimental treatments will be replicated five times.
Cover Crop Method and Tillage Timing Trials
We will compare current conventional tillage potato/grain production to a modified version of the research conducted by Griffin et. al., that would include underseeded vs. monocropped small grains. Underseeded (annual ryegrass) plots would include treatments of postharvest tillage (late summer), late fall chemical desiccation, or spring tillage. Monocropped plots would include treatments of fall tillage, fall tillage plus spring oat cover, fall tillage plus cereal rye cover with spring chemical desiccation, or spring tillage of monocrop stubble.
Plots (grain phase) will be established at the Aroostook Experiment Station in spring of 2017. The seven treatments will be organized as a randomized complete block design with four replications. Grain yields and quality parameters will be recorded. Fall and spring ground cover will be recorded preceding the potato phase. Spring ground temperatures and moisture levels will be recorded for individual treatments. Russet Burbank potatoes will be planted in the spring of 2018. Yield and quality parameters will be recorded in the fall at harvest.
Local standard crop care practices (pesticide applications, cultivation) will be conducted by research farm staff.
Comparative cropping budgets will be estimated for each treatment of the cover crop/tillage timing trial to assess the potential return to growers for adoption of a particular practice.
Twilight Meeting- We propose to conduct a twilight meeting at the Aroostook Experiment Station in which we will send invitations to our grower mailing list (300 potato growers). We will likely look to conduct this in July 2017 and July 2018. We will conduct a presentation on the research, current observations, and provide a brief tour of the plots. We expect 15-20 growers to attend these meetings each year.
Maine Potato Conference- The annual Maine Potato Conference is conducted each January in Caribou, ME. We propose to provide one to two presentations on this research for the 2018 and/or 2019 conferences. Approximately 200 growers, consultants, and university staff and faculty attend each year.
Maine Grain Conference- The Maine Grain conference is conducted annually during the month of March. We propose to provide a presentation at this conference in 2018. Approximately 60-80 growers, consultants, and university staff and faculty attend each year.
Maine Grain and Oilseed Newsletter- We propose to write an article about this research and demonstration that will be disseminated through this newsletter (700+ subscribers including potato mailing list).
The potato production systems in the Northeast are predominantly two-year rotations of potato and small grains (barley, oats, or wheat). With a short growing season, potato production in the Northeast doesn’t provide much opportunity for cover-cropping, with potato harvest occurring during the last half of September through the first half of October. In the grain production phase of the rotation, the practice of post-harvest primary tillage dominates the region in order to provide early preparation and planting of the subsequent potato crop in the spring.
With our current production system there are several points where the risk for soil loss is high. With little crop residue and potentially compacted soils from field traffic, the period after potato harvest is one concern. Another is the late summer/fall tillage of small grain ground eliminating crop stubble or regrowth of underseedings (clover, annual ryegrass). This practice exposes soils to potential erosion and runoff from fall rains and spring snowmelt. Lastly, the time period from potato planting to row-closure is sensitive to erosion and runoff events and has recently gained prominent attention in recent years owing to our increase in early summer high-intensity rain events (> 2” per hour events) causing significant damage to fields and roadsides, and leading to visible water pollution issues.
Recently, planting small grain nurse crops at planting has been explored to provide soil protection and reduce soil loss during the period from potato planting to row closure. This project has been initiated by McCain Foods field staff in conjunction with local on-farm cooperators. Nurse crops can improve rainfall infiltration, the roots hold soil in place, and possibly improve N cycling in the soil system (Hoorman, 2009; Mitchell, 1995). While this type of practice has been used in some vegetable and sugar beet production (LeBlanc, 2014; Fornstrom and Miller, 2008), this practice is new to potatoes. The development of another practice, one-pass hilling, has made this practice economically feasible. While growers are optimistic about nurse cropping to reduce soil loss, McCain agronomists have found mixed results.
Griffin et. al. (2009) conducted research on delaying tillage and the effects of cover cropping in potato systems in Maine (2002-2005). In their research they compared agronomic effects on potatoes and barley of spring tillage vs. fall tillage of small grain (with or without underseeding) ahead of potatoes, and no-tilling of grain into potato crop residue the spring following potato harvest.
Despite the success of this conducted research, the practices outlined within it have not been adopted. Working with a small group of potato producers, we have identified some alternative practices to research and demonstrate that could produce a more amenable recommendation to the industry. Of most concern to these producers is sufficient time to plant their potato crop.
Many view the potentially excessive amount of green biomass worked into the soil in the spring to be a detriment that would set back planting times; owing to the time to breakdown the soil-incorporated cover and the potential for slowed drying and warmup of the soil. Tillage of a wet field prior to planting is most problematic at harvest as soil clods decrease harvest efficiency and possibly cause tuber damage (bruising and nicking).
In the summer of 2017, two trials were initiated at each of two locations in Maine (four trials total). Nurse crops and rotation studies were evaluated in Orono and Presque Isle Maine. In the nurse crop trial, the fields were prepared in May. In Orono, fertilizer was banded in the soil as the rows were marked by the planter. Nurse crop treatments were broadcast across the soil surface and a lely cultivator was used to scratch the surface and slightly incorporate seeds. In Presque Isle, nurse crop treatments were broadcast, and seed was planted with a potato planter. Nurse Crop treatments we compared included 100 and 200 lbs seed/ac rates for both cereal rye and oats. Another set of treatments were broadcast at 100 and 200 lbs/ac with these plots being killed with herbicide prior to hilling. Finally we sowed cereal rye at 100 lbs/ac and allowed those treatments to grow an additional week to determine if we could get another week of protection at no cost to the crop.
Biomass counts and samples were taken at three and four weeks after planting. Leaf petioles were collected from the 4th leaflet from the top of the plant in July to see if the nurse crop affected yield or potato quality. For yield and quality we sampled 15 feet of row and washed and graded these in storage.
The potato rotation study was started in early may by sowing barley a 1M seeds/ac and undersowing three of the treatments with annual ryegrass. The barley was combined off in early august. One of the undersown plots was disked two days after harvest. The other two annual rye under-sown plots were allowed to grow. Winter rye and oat cover crops were sown at a 150 lb/ac rate. One of the undersown annual rye grass was sprayed with glyphosate at the end of the season. Biomass samples of the actively growing cover crops were made in late November. Next year the soils will be worked and potatoes planted to see how they respond.
I have two years of data collected on nurse cropping from the Orono location, and we started with two locations of the rotation crop. My partner put the trials in at a farm because he had little opportunity at the UM research farm. There was an error with the nurse crop fertility and only about half of the fertilizer N was applied. It was not corrected. So the trial was most affected by that and less so the treatments.
The rotation trial was started according to plan. The barley was sown and the underseedings were done, but there was no combine at this farm to do the harvest in August. He lined a couple of farmers up to take off the grain, but they fell through. He didn’t put the cover crops down. So I’ll have one site to report on instead of two next year when we grow the potatoes.
Research conclusions at this stage are as follows: Nurse crops can effectively armor the soil from erosion, but they do not affect N fertility, and they do not affect yield. As a result, we have to pitch a practice to growers that will effectively protect their soil but will increase that cost of production. This means growers have to invest to seed down the field and hill it in when they don’t see a bottom line yield increase. For farmers with sloping ground, it is a practice that should be employed. Getting farmers fired up to do it without a probability of a yield increase will be a hard sell, but maybe it can be packaged in a series of practices that may warrant a higher contract price. Time will tell.
Education & Outreach Activities and Participation Summary
Two presentations were delivered on nurse cropping in potatoes at the NY/NE certified crop advisor training in Syracuse in November 2017. The room was filled with ag eduators and consultants. I also presented this to growers at the NE Fruit and Vegetable conference in Manchester in December, at two field day events during the summer.
The second trial will be the focus of the educational programs next year once we have some data from the potato part of the rotation.