1966] FRENCH AND BLAKE: TILLAGE FOR POTATOES 375

Transcription

1 1966] FRENCH AND BLAKE: TILLAGE FOR POTATOES 375 NEWS AND REVIEWS PRIMARY TILLAGE FOR POTATOES 1 G. W. FRENCH AND G. R. BLAKE 2 Cultivation and tillage methods for potatoes fall into four categories: a) initial loosening of the soil, b) secondary, preplant tillage, c) pre-emergence tillage, and d) post-emergence tillage. This paper deals with the first two categories. It is generally accepted that plowing is necessary for initial loosening of the soil, though there are few data to support this. Jacob and Russell (4) found on Long Island, New York, that disking produced lower yields than plowing. They did not identify the previous crop nor the soil type, though the soil was probably sandy loam in texture. Several researchers have found no response to cultivation where the weeds were controlled by hoeing or scraping (5, 6, 8). With herbicidal weed control, more than one cultivation was found to be unnecessary on sandy loam or loamy sands in New Jersey (1). Ridging is believed to be beneficial on fine-textured soil and/or where precipitation is great (3), but ridging is seldom necessary to produce high yields (3, 7, 9). In 1958, 1959 and 1950, Blake, French and Nylund (2) conducted experiments designed primarily to test various secondary, pre-emergence and post-emergence tillage practices on fine textured soils, high in organic matter content, in the Red River Valley of Minnesota-North Dakota. Primary tillage (initial loosening) was uniformly fall plowing of wheat stubble. They found that no secondary, preplant tillage gave as high Red Pontiac yields as any tested other treatment. Where weeds were controlled by an herbicide there was no yield advantage to three cultivations over one cultivation. The experiments reported here were designed to investigate the effects of primary tillage on potato yields, incidnce of clods at harvest time, digger draft, and quality of tubers. METHODS AND MATERIALS This investigation of the effects of primary tillage practices on potato production was initiated in the fall of 1960 with the first planting being made in the spring of The experiment was repeated in and Each year the plots were established on land previously in spring wheat. After combining wheat, no implement of any kind was used on the land prior to application of the experimental primary tillage treatments. The primary tillage treatments are listed below: 1--No primary tillage of any kind. Potatoes were planted in the undisturbed wheat stubble. 1Paper No presented at the Annual Meeting of the American Society of Agricultural Engineers at Fort Collins, Colo., June 1964, on a program arranged by the Power and Machinery Division. =Respectively, Agricultural Engineer, Red River Valley Potato Research Center, AERD, ARS, USDA, Grand Forks, N.D., and professor, Department of Soll Science, University of Minnesota, St. Paul. This article is r~printed with authors changes from the TRANSACTIONS Of the ASAE (vol. 8, no. 2, pp. 246, 247 and 248, 1965), the Transactions of the American Society of Agricultural Engineers, Saint Joseph, Michigan.

2 376 AMERICAN POTATO JOURNAL [Vol Deep tillage in the fall. This treatment was applied with a tractormounted implement using chisel points spaced 11 in. apart. The soil working depth was approximately 10 in. 3--Plow with a moldboard plow to a depth of 6 in. in the fall. 4 Deep tillage in the spring. Except for time of application, this treatment was identical with treatment Plow with a moldboard plow in the spring to a depth of 6 in. No secondary preplant tillage was used. The above described experimental treatments constituted the only tillage applied prior to planting of the potatoes. Treatments 2 and 3 were applied in October each year. Treatments 4 and 5 were applied one day before planting, except in 1962, when planting was delayed four days due to rain. Plots were located at the Red Valley potato growers research farm, five miles south of Grand Forks, N. D., on Bearden silty clay loam, a different experimental range being used each year. The soil is a lacustrine calcium carbonate Solonchak, with an organic matter content of about 6.5 percent and a ph of 8.0. The soil is nearly level and is moderately poorly drained. Fertilizer elemental analysis ( conventional) was applied in two bands by belt distributors on the planter. All plots received equal amounts of fertilizer in any one year. The application rates were uniform for treatment in any year, being 350, 430, and 600 lb per acre, respectively, for Planting was accomplished with an assisted-feed, two-row potato planter. Two 6-in. sweeps were attached to the tractor-mounted toolbar for the purpose of insuring uniform penetration of the furrow openers. These sweeps were 38 in. apart, in line with the furrow openers and were adjusted to a working depth of about three inches. Certified Red Pontiac seed potatoes were used each year. "B" size (average weight, 189 oz) whole tubers were planted 12 inches apart in rows spaced 38 inches. Early weed growth was destroyed by the furrow openers and covering disks on the planter. Even in those treatments (1, 2, and 3) receiving no tillage in the spring, weed control presented no difficulty. Early weed growth between the rows was eliminated by the first cultivation, which was applied before emergence of the potato plants each year. Cultivation was not an experimental factor, nor was there any predetermined schedule followed. The timing and implement used was based on prevailing weed growth. All plots, in a given year, received identical pre-emergence and post-emergence tillage, i.e., one pre-emergence cultivation, a regular cultivation, and a final hilling of the rows. Plots were dragged two times with a spike-tooth harrow in 1962 and with a springtine weeder in 1963 between the first and second cultivations. Fungicides and insecticides were uniformly sprayed on all plots as needed. The experimental design consisted of five treatments randomized in each of eight replications. Plots were 25 ft long in the direction of the rows and 63.7 ft in width (20 rows). Twelve rows, at least one row removed from concentraetd sprayer traffic, were harvested from each plot. Seedbed preparation was accomplished with the tractor and implements traveling across the area perpendicular to the intended direction of the rows. Planting was continuous from plot to plot, potato plants

3 1966] FRENCH AND BLAKE: TILLAGE FOR POTATOES 377 being removed from a 3-ft buffer between treatments prior to tuber development. Potatoes were harvested with a two-row, open-throat potato digger equipped with a driven 7~-in square rod blade-substitute and a side-. delivery windrower. A canvas strip 3 by 10 ft was mounted on a roller beneath the windrower in such a way that it could be tripped during digging. As it unrolled along the row, potatoes, clods, and loose soil carried over the digger apron were caught for sampling. Potatoes were removed and clods were separated from vines by pouring them in a wire picking basket for weighing. Digger draft was indicated on a pressure gauge actuated by a specially designed hydraulic hitch. Penetrability was measured with a Meyenburg continuous recording force-depth penetrometer midway between the potato ridge and the furrow. April through September precipitation varied considerably during the experimental period as shown in Table 1. The times of applying the spring tillage and planting are shown in Table 2. TABLE 1.--Precipitation (inches) April through September at experimental site Departure Departure Departure Total from normal* Total from normal* Total from normal* April May June July August September Totals *Departures from normal are based upon climatological data recorded at University of North Dakota station. TABLE 2.--Dates of performance of spring applied field operations. Operation Deep tillage or plowing... May 22 June 7 May 7 Planting... May 23 June 11 May 8 First cultivation... June 9 June 13 June 3 Harvested... Oct. 4 Oct. 3 Sept. 12 TABLE &--Yield of potatoes as related to primary tillage. (cwt/acre) Three-year Treatnlent average No tillage a 192a 131a 163a Deep till, fall a 129a 155ab Plow, fall a 195a 105 c 150 b Deep till, spring a 188a 12lab 156ab Plow, spring a 158 b 113 bc 139 c *Means in a column not followed by the same letter are significantly different. Means followed by the same letter are not significantly different.

4 378 AMERICAN POTATO JOURNAL [Vol. 43 RESULTS AND DISCUSSION Effect of tillage treatment on soil water at planting time Soil samples were taken each year near planting time. There was a trend toward higher moisture content in the plots which received no fall tillage than in those that had been deep-tilled or plowed in the fall. Except for the 0 inch to 4 inch depth, the differences did not prove to be statictically significant. Relative rates of plant emergence Stand counts were made on several dates in 1961 and 1962 after substantial emergence of plants was apparent. Multiple stems from a single tuber were counted as one plant. A slight negative relationship between relative emergence rate and soil water content was noted in The higher 0-4 inch water content may have resulted in lower soil temperatures that delayed early emergence. In 1961, early stand counts revealed significantly lower emergence with no primary tillage. A temperature effect of surface residue may have also resulted on the no-tillage treatment. At any rate, there was no effect of treatment on ulimate emergence in 1961 and Clods carried over digger apron Clods carried over the digger apron were weighed in 1962 and Clod measurements were planned in 1961, but there were virtually no clods associated with any of the treatments that vear. There were wide variations in amounts of clods between replications of the same treatment. This suggests that clod formation is strongly influenced by factors other than preplant tillage. Undoubtedly, soil water content at harvest time accounts for some of the variaions. In 1962, notillage and fall-applied-tillage resulted in significantly feewr clods than resulted from the application of tillage treatments in the spring. In 1963, the differences in amounts of clods did not prove to be significant. Digger Draft A direct-reading hydraulic gauge with a maximum pressure indicator was used in conjunction with a hydraulic hitch to measure draft. It was apparent that the draft varied considerably as the tractor and digger traversed a single plot. The only practical indication that could be recorded similarly for each plot was the maximum draft. The maximum-pressure indicator was reset while the tractor and digger were stopped between plots. In each of the years, the draft associated with no tillage and spring tillage was higher than for fall tillage, though only in 1962 did the differences in draft prove to be statistically significant. The highest average nmximum draft was only 12 to 13 percent above the lowest average draft in each year, a difference of relatively little importance. No valid comparisons between years can be made since the depth adjustment was not necessarily the same from year to year. The draft ranking is similar to penetrability ranking. Penetration Force Force required to penetrate the soil with a pointed probe at constant velocity was measured once in 1961 and 1963 and twice in Trends were the same at all sampling times with only minor variations in treatment rankings for time of sampling and depth. No preplant tillage

5 1965] FRENCH AND BLAKE: TILLAGE FOR POTATOES 379 gave high penetrometer force, spring plowing low, with other treatments intermediate. Yield of Potatoes Potatoes were hand-picked and weighed in the field. Since no effect of secondary preplant tillage on tuber size distribution had been found in a previous sudy (2), potatoes were not size graded. Potato yields are shown in Table 3. The no-tillage treatment produced as high yields as any other treatment in all years. Indeed there was a trend for this treatment to outyield others in all years. As an average for the three years, plowing either in the fall or the spring, gave significantly lower yields than no preplant tillage. Spring plowing gave generally lower yields in all years than other treatments. Fall plowing varied with year; in 1962 it gave the highest and in 1963 the lowest yield of all treatments and years. There was also a tendency for lower soil moisture on fall-plowed plots at planting time in all years. It is speculated that the relatively lower yield for fall plowing in 1963 may have been related to moisture deficiency in view of the very low May and June rainfall in that year. Conversely, in 1962, a year of high May rainfall, the lower water content of fall-plowed plots was not a disadvantage to yields for fall plowing in that year. Three-year average yields show that plowing, especially in the spring, resulted in lowered yield. And, indeed, farmer practice on these soils trends decidedly toward some kind of heavy field cultivator or deep-tillage tines as a substitute for moldboard plowing. SVZdMARY In the three years this experiment was conducted, omitting primary pre-plant tillage for potatoes following wheat the previous year, gave as high yields as any of four other treatments. Early emergence rates seemed to be adversely affected by the no-tillage treatment, but final emergence was not affected. There was some indication that deep tillage or plowing in the spring resulted in more clods at harvest time. Potato digger draft was not markedly affected by primary tillage treatment. Plowing in fall or spring was detrimental to yield as compared to no tillage, except that fall plowing gave good results in a year of high May rainfall. Although there was a trend toward lower yields with deep tillage than with no tillage, differences among these three treatments were not statistically significant. In 1961 and 1962, planting of all five of the primary-tiuage treatments was accomplished with no unusual difficulty. In 1963, considerable difficulty was experienced in planting plots which had not been plowed. The amount of straw was much greater than in the two preceding years and straw frequently clogged the furrow-opener disks. Some difficulty was caused by straw during the first cultivation. Later, cultivations were carried out without interference by the straw on any of the treatments. Excessive amounts of straw have been known to induce scab (10). In the present experiments, little straw came in close proximity to the seed tubers in the unplowed plots. During successive cultivations, most of the straw was incorporated in the ridge above the zone of tuber growth. Virtually no scab was noted in any of the treatments.

6 380 AMERICAN POTATO JOURNAL [Vol. 43 Weeds were controlled entirely by mechanical means. It was apparent that early weed growth was much greater on the unplowed plots prior to planting of the potatoes. As stated before, weeds in the rows were eliminated by the furrow openers of the planter. Weeds remaining in the middles were subsequently eliminated by cultivation. After the second cultivation, there were no apparent differences among treatments in respect to weed control. Complete control was achieved each year by cultivations applied uniformly to all plots. It is emphasized that the results herein described apply to Bearden silty clay loam under the climatic conditions of the Red River Valley of Minnesota-North Dakota. While it is probable that minimum-tillage principles are universally applicable, some adjustments may be required to fit local soil and climatic conditions. LITERATURE CITED 1. Blake, G. R. and R. J. Aldrich Effects of cultivation on some soll physical properties and on some potato and corn yields. Soii Sci. Soc. Am. Proc. 19: Blake, G. R., G. W. French and R. E. Nylund Seedbed preparation and cultivation studies on potatoes. Amer. Pot. J. 39: Hardenburg, E. V Efficiency factors in cultivation of potatoes. Amer. Potato J. 10: Jacob, W. C. and M. B. Russell The effect of tillage practices on the yield of Irish Cobbler potatoes. Amer. Potato J. 29: Lombard, P. M Comparative influence of different tillage practices on the yield of Katahdin potato in Maine. Amer. Pot. J. 13 : Merkle, R. G. and G. J. Irvin Some effects of intertillage on crops and soils. Pa. Agr. Exp. Sta. Bull., Moore, G. C The effects of certain methods of potato cultivation on growth and yield and accompanying soil conditions. Amer. Pot. J. 14: Thompson, H. C., et al Cultivation experiments with certain vegetable crops on Long Island. New York (Cornell) Agr. Exp. Sta. Bull Werner, H. D Cultivation of potatoes under western conditions. Amer. Potato J. 10 : Sandar, N Control of russet scab in potatoes. No. Dakota's Agr. Exp. Sta. Bi-monthly Bull. May-June,reprint No. 462.