Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701) 742-2700, email: rgreenla@ndsuext.nodak.edu

Furrow vs. Hill Planting of Irrigated Potatoes

2001-2003 Replicated Plot Studies

Dean Steele, Richard Greenland, and Harlene Hatterman-Valenti

Executive Summary

     Three years (2001-2003) of replicated plot studies at Dawson and Tappen, ND using a single plant population (in-row seed spacing) and a single nitrogen fertility rate have shown that compared with hill planting, potatoes planted in furrows produced 24% larger average tuber size (6.62 vs. 5.33 oz., based on weighing individual tubers), and averages of 40% more yield in the 6 oz. and larger tuber size category (281 vs. 201 cwt/ac), 17% more yield in the 4 oz. and larger category (354 vs. 302 cwt/ac), and 10% more total yield (412 vs. 374 cwt/acre; the total yield value was not statistically significant). Results from 2001-2003 plot studies at Oakes have generally been more even between furrows and hills, but under significant disease pressures. There have been essentially no differences in tuber quality between the furrow and hill planting techniques.

     The rationale for this research is that for sprinkler irrigated potato production on coarse-textured soils, water movement on the soil surface from the hill to the furrow may hinder plants in their capture of water and nutrients. In contrast to the conventional hill configuration, a furrow planting configuration with a midrow ridge may offer the plants a water harvesting effect that can reduce crop stress, improve tuber production, and maintain tuber quality. The objective of this research project has been to determine whether a furrow planting configuration holds any advantages over hill planting as measured by tuber yield and quality.

Project Description

     A third year of replicated plot research was conducted in 2003 near Tappen, ND and near Oakes, ND to determine whether a furrow planting configuration is more productive than the conventional hill configuration for irrigated potatoes on well-drained soils. At each site, all the furrow and hill planted plots were treated identically with respect to schedules and amounts of irrigation, fertilizer, herbicide, and fungicide, using production practices typical of those for potatoes grown in the conventional (or hill) configuration.

     The research has used small plots (each 12 ft wide by 40 ft long), the Russet Burbank variety, a row spacing of 36 inches, and an in-row plant spacing of approximately 12 inches. A two-row planter has been modified to accomplish both the hill and furrow planting. Use of the same planter for both configurations eliminates variation from factors such as seed spacing, row width, and insecticide application amounts. Soil temperature and soil moisture tension were measured hourly at 6- and 12-inch depths in the crop row and between crop rows, and at the seed piece depth. Soil moisture and soil temperature were measured in one replication of each type of plot at each site, not in all plots at both sites. Use of sensors in all plots would have been prohibitive in terms of labor and instrumentation requirements. We are using the soil moisture and temperature measurements to identify trends, not to make statistical comparisons between treatments.

     For the 2001-2003 seasons at Oakes, hill and furrow planting configurations were used as treatments in a randomized complete block experimental design with six replications. Fisher's F-protected LSD test at the 0.05 level of significance was used for all statistical comparisons of yield reported herein.

     At both Oakes and Tappen in 2003, harvest areas consisted of 25-ft lengths from the middle two rows in each plot. All tubers from each plot's harvest area were individually weighed at the USDA-ARS Potato Research Worksite in East Grand Forks, MN. Yield results were summarized for each experimental unit (plot) by individually weighing the tubers and sorting the tuber mass (M) data into the following size categories: very small, i.e., M < 113 g (M < 4 oz.) excluding culls; small, 113 ≤ M < 170 g (4 ≤ M < 6 oz.); medium, 170 ≤ M < 283 g (6 ≤ M < 10 oz.); large, 283 ≤ M < 454 g (10 ≤ M < 16 oz.); very large, M ≥ 454 g (M ≥16 oz.); M ≥ 130 g (4 oz.); M < 130 g (4 oz.) including culls; M ≥ 170 g (6 oz.); M < 170 g (6 oz.) including culls; culls (tubers with growth cracks, green spots, excessive knobbiness, spoiled or rotten tubers, etc.); and total yield (all tubers). We tested tubers for specific gravity, the incidence (but not severity) of hollow heart defects, and French fry color. For hollow heart classification, we marked a tuber as having the hollow heart defect regardless of the size of the internal crack, split, or cavity.

     We measured soil moisture using the capacitance-type soil moisture sensor (HydroSense, Campbell Scientific, Logan, UT) in the top 20 cm (8 in.) of soil at multiple sites and dates in 2003. At each field site and sampling date, approximately twenty-five to thirty measurements of volumetric moisture content were taken with capacitance sensor along each of three transects or lines through the plots. The first transect consisted of measurements approximately midway between plants in the hill or ridge of hill-planted potatoes. The second transect consisted of measurements offset from the first set, i.e., in the adjacent furrow of hill-planted potatoes. The third transect consisted of measurements approximately midway between plants in the furrow of furrow-planted potatoes. Approximately ten soil cores were taken adjacent to selected capacitance sensor readings to obtain soil for moisture content determinations and site- or soil-specific calibration of the sensor. Soil cores were placed in sealed metal cans, transported to the laboratory at NDSU in Fargo, and oven dried for 24 hours at 105 ̊C, which is the standard method for soil moisture content determinations. Linear calibrations of volumetric moisture content vs. capacitance sensor period (a time constant) have produced coefficients of determination (r²) values ranging from 0.64 to 0.94, which means the capacitance sensor appears to be a reliable and accurate method for soil moisture measurement if calibrated for the soils at each site.

     Most soil moisture data sets based on the capacitance sensor were collected for a single date in 2003, but a pre- and post-irrigation sampling approach was used for one irrigation event at Oakes to determine whether furrows were more efficient at capturing water compared with hills. An initial set of readings was taken on 7 August, followed immediately by 0.71 inch (18 mm) of irrigation. Approximately 24 hours later, a second set of readings was taken. The time lag of one day is commonly accepted as necessary for moisture redistribution in coarse-textured soils.

Results

     A composite analysis of variance for three years at the Dawson and Tappen, ND sites indicates that both the furrow shallow and the furrow deep planting configurations produced significantly larger average tuber size, greater yield of tubers larger than 4 oz., and greater yield of tubers larger than 6 oz. compared with either the hill shallow or the hill deep planting configurations. Mean values of total yield could not be compared at this level (split plot) of the three-year experiment because of a significant year x split-plot interaction.

     For the experiments at Oakes, a three-year analysis of variance for the 2001, 2002, and 2003 seasons indicated no significant differences between furrow and hill planting for any tuber size, yield, or quality parameter. Field plots at Oakes were adversely affected by a herbicide burn injury in 2001, verticillium and black dot disease pressures in 2002, and rhizoctonia and verticillium in 2003.

     Soil moisture measurements indicate that the furrows (in both the hill and the furrow planting configurations) were significantly wetter than the hills in the hill-planted areas. Based on pre- and post-irrigation measurements at Oakes during 7-8 August 2003, soil in the furrows showed significantly greater gains in moisture content compared with the hills. Table 85 shows that before the irrigation, the soil in the ridge position was approximately five percentage points drier than the soil in either furrow position. These measurements demonstrate the concept that the furrows are wetter than the hills, even in coarse-textured, well-drained soils. After the irrigation event, the ridge position showed very little gain in moisture content (0.9%), while the furrow positions both showed gains of approximately 5% in moisture content.

     The larger gains in moisture content for the furrow position illustrate that the furrow planting configuration produces a real water harvesting effect. The movement of water toward the plant in the furrow, rather than away from the plants in the hill, reduces the severity of drought stress on the plants and appears to allow the plant a better environment for tuber production, as illustrated by the shifts in the tuber size distribution noted above.

Table 85. Soil moisture (percent volumetric moisture content) immediately before and approximately 24 hours after a 0.71-inch irrigation at Oakes, ND in 2003.

Conclusions

          Comparisons of furrow and hill planted plots (taken from all three sites) have indicated the following over the three years of replicated studies:

1.  The furrow planting configuration produces strong shifts toward larger tuber size and greater yields in the larger tuber size categories under normal growing conditions.

2.  Furrow-planted potatoes have held up as well or better than potatoes planted in the hill configuration under disease pressures.

3.  Measurements of soil moisture indicate that the furrow planting technique produces a wetter and more uniformly moist root zone environment in the crop row compared with the hill planting technique.

4.  In some cases the furrow-planted potatoes emerged more quickly than the hill-planted potatoes.

5.  Because of faster emergence and canopy development, soil temperatures have been observed to be cooler as a result of better shading for the furrow-planted plots, which has implications for thermal stress and the sugar end defect.

6.  We have observed no differences in specific gravity, the incidence of hollow heart, or French fry color for furrow vs. hill configurations.

7.  Harvesting in the furrow has not posed a problem for our plot-scale harvesting equipment, which is similar in principle to commercial machinery.

8.  We have observed virtually no green or sun-scalded tubers in any of these studies.

9.  We recognize that furrow planting does not appear to be appropriate for fine-textured or heavy soils, nor for situations of extreme over-irrigation.

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