Deep N Use: How Sunflower Compares With Other Crop
Three years of central North Dakota comparisons of sunflower and other crops on their effectiveness of deep nitrogen use have yielded some interesting preliminary findings.
The comparisons have encompassed three methodologies: a survey of commercial farm fields in two central North Dakota counties; a field survey on location at the NDSU Carrington Research Extension Center (CREC); and a cropping systems trial at the CREC. Project coordinators have been Ezra Aberle and Yvonne Lawley of the NDSU-Carrington staff.
Here’s a synopsis of what’s been done to date, including basic findings:
• In the fall of 2008, four fields at the CREC that had hosted sunflower, canola, barley and wheat trials, respectively, were sampled to a 4’ depth. Three samples were taken within each field. Deep soil nitrate levels for the samples ranged from 12 to 84 lbs/ac, but there were no significant differences in average deep soil N between any of the fields.
• That same fall, in a cropping systems study at CREC, soil samples from 0-4’ were taken from the 50-lb/ac fertility treatment in the four different crop fields. The objective was to compare residual deep soil N following each of those crops under different tillage systems — namely, conventional, minimum-till and no-till. “Because the data were unreplicated, no statistical comparisons can be made between the treatments,” Aberle and Lawley state. “But data trends suggested that further investigation is warranted to substantiate differences between tillage systems.” For sunflower specifically, the lowest deep soil N level occurred under no-till.
• A farm field survey was conducted in November of 2009. Soil samples were collected from 10 pairs of neighboring fields in Foster and Stutsman counties following the sunflower and small grain harvests. Each field was split into two management areas, based on soil type and topography, to account for variability within a field. Soils were sampled at 0-2’ and 2-4’. When deep soil N was averaged across all 10 pairs of fields, there was no statistical difference between sunflower and small grains.
• A cropping systems trial was conducted at the CREC in the fall of both 2009 and 2010. Samples were collected from three treatment replications, with 50 lbs N applied to the sunflower. The data compared “before and after” deep soil N for sunflower in the three tillage systems. “There were numerical differences in the means between sunflower and spring wheat within tillage systems,” Aberle and Lawler report. “However, they were not statistically different across years.”
The Carrington researchers plan to continue their deep N sampling in 2011 to expand their dataset. They also are planning a grower field survey in both the spring and fall of 2011, allowing for “before and after” comparisons of deep soil N for sunflower. “This survey, coupled with the cropping systems dataset, may give better resolution to differences between treatments that was not possible with the preliminary sampling that happened in 2008 or the on-farm survey work in 2009,” they observe.
Any grower within about a 30-mile radius of Carrington willing to cooperate with the 2011 field survey is invited to contact Aberle at (701) 652-2425. - Don Lilleboe
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