The winter of 1989/90 experienced high winds which created substantial topsoil loss. Windbreaks might aid in reducing top soil loss in these times. A study is reviewed in this paper regarding attempts to discover if windbreaks placed at varying distances, enhanced corn and potato yields. Thinning, fertilizer application and root pruning were applied in this study

Chaput, L. J.

Tuskan, Gerald A.

NDSU Libraries Institutional Repository

Field Windbreak Management and Its Effect on Adjacent Crop Yield APreliminary Investigation L.J. Chaput and G.A. Tuskan The devastating effects of high wind on North Dakota top­soil was witnessed throughout the state during the winter of 1989-90. Fields unprotected by crop stubble or windbreak plantings were vulnerable to extensive wind erosion. Wide­spread planting of single-row field windbreaks has been done in the past and continues today to help reduce such erosion. Field windbreaks do play an important role in pre­venting the loss of valuable topsoil. One criticism of field windbreaks, however, is that these plantings can reduce crop yields immediately adjacent to the windbreak (Greb and Black, 1961; Frank et al. , 1974; lahar and Brandle , 1978) . Trees may compete directly with crops for moisture and nutrients, resulting in decreased plant height and re­duced yield . Windbreak management may proVide a way to minimize competition between trees and crops (Frank, 1979; Um­land, 1979). The follOWing study was initiated in the spring of 1989 with the objectives of 1) implementing prescribed management practices on selected single-row field wind­breaks and 2) monitoring crop yields at prescribed distances away from the windbreak. MATERIALS AND METHODS Two mature, healthy, single-row fie ld windbreaks were selected for this investigation. The first , located near Ab­saraka on Gardena sandy loam soil , was a 27-year-old, 36 feet high green ash (Fraxinus pennsyluanica Marsh.) wind­break, interplanted with American plum (Prunus americana Marsh.). The second was a 20-year-old, 30 feet high Siber­ian elm (Ulmus pumila L.) windbreak located at the Red River Valley Potato Research Farm south of Grand Forks on Bearden clay loam soil . A 2, 400 feet length of trees in each windbreak was divided into four 600 feet sections, one for each of the four corresponding cultural treatments : thinning, fertilizing, root pruning and contra!' The width of these four treatment blocks, located on the windward side of the wind­break, was determined by calculating the average height of each windbreak and multiplying that value by 10.5 . This proVided the necessary width in each treatment block to allow the collection of yield data at four prescribed distances away from the windbreak (lH , 2H, 5H and 10H) . These distances corresponded to IX, 2X, 5X and lOX the average height of each windbreak. Chaput is research specialist and Tuskan is associate professor, Department of Horticu lture and Forestry . Thinning Manual thinning was done at the Absaraka site between May 1-4. Green ash with multiple stems originating from ground level were cut back to a single stem. Final spacing for the green ash in the thinned section was approximately 9 feet between stems. On each of the remaining stems , all lower limbs were removed to a 6-foot height above ground. All of the American plum (P/unus americana Marsh.) under­story plants in the thinning treatment were removed at ground level using a brush cutter. The cut stumps were sprayed with 2,4-0 to prevent regrowth. A small percentage of plum did resprout. These were again removed. The S iberian elm windbreak at Grand Forks was thinned be­tween May 8 -10, using the same thinning criteria as de­scribed for the green ash windbreak. Thinning the Siberian elm windbreak to 9 feet between stems was difficult since the distance between trees was more variable, ranging from 2 feet between trees in some sections and up to 12 feet in other sections where trees had died out. The Siberian elm windbreak did not have an understory species . Final spacing between trees was approximately 9 feet. Fertilizer Soil was sampled in the 600 foot x 380 foot fert ilizer treat­ment block at depths of 0 to 6 inches, 6 to 24 inches, and 24 to 48 inches at the Absaraka site which was to be planted to corn, and 0 to 6 inches and 6 to 24 inches at the Grand Forks site which was to be planted to potatoes . Composite samples from the various depths were analyzed at the NDSU Soil Testing Lab for macro- and micronutrients, pH and organiC matter content. Analysis resu lts were used to determine levels of nutrients to apply for each crop in­volved. At the Absaraka site a 37-13-0 N-P-K granular fer­til izer was un iformly applied to the ferti lizer treatment block with a Tandy drop spreader fertilizer attachment. At the Grand Forks site 'a 30-75-60 N-P-K granual fertilizer was commercially applied to the fertilizer treatment block with a T erragator drop spreader fertilizer implement. Root Pruning A 24 inch long, Single-blade, three-point mounted imple­ment was used to prune tree roots in the root pruning treat­ment. A double pass was made at a distance eqUivalent to three-fourths the average height of each tree row (.75H) on the windward side of each windbreak. The first pass was made at a 12 inch depth, and the second pass was made in the same trench in the reverse direction at the final depth of 24 inches . Control A single control block was used for comparisons to the ap­plied treatments. The control plots received none of the 26 above treatments. Standard farm practices were implemen ­ detected for plants per acre, number of ears per plant, aver ­ted at each location for each crop. age ear diameter, kernel depth, kernel rows per ear. percent stem lodging, percent root lodging, or percent ear drop . Yield Measurements 'Garst 8939' hybrid fie ld corn was planted on May 15 at the Absaraka site and the potato cultivar 'Monona' was planted on May 17 at the Grand Forks site . Routine cultiva ­tion was done at both sites across all treatments to control weed populations . There were 16 plots per treatment (4 d istances X 4 replicates). Four distances from the windbreak were chosen as target strips to monitor crop yield : I H , 2H, 5H and 10H. The corn was hand-harvested on October 19. Ears from a 20 foot length of row from each of two adjacent rows in each plot were harvested, weighed and dried down to 4 percent moisture content. Data included : plants per acre, number of ears per plant , total wet weight , total dry weight, test weight, hundred kernel weight, average ear length, average ear diameter, kernel depth) kernel rows per ear , kernels per row, percent stem lodging, percent root lodging and percent ear drop. Yield per plot in bushels per acre was calc ulated at 15 .5 percen t fie ld moisture . Potato samples were harvested on September 15. A mechanical harvester was used to harvest the tubers from a hundred foot length of row from each plot. Tubers were weighed and total weight per plot was recorded . Yield per acre was calcu­lated. RESULTS Corn Yield Composite yields were combined across the four dis­tances for each treatment. S ignificant differences were found in yields between the thinning treatment (91 bushels per acre) and the control (67 bushels per acre) .. Yields. for the thin ning treatment were not significantly greater than yields from the fert ilizer or root pruning treatments (Table 1). Hundred kernel weights and test weights for a ll three treatments were Significantly greater than the control, with the fertilizer treatment producing the highest hundred kernel weight and the thinning treatment producing the highest test weight. Average ear length for the thinning treatment (6 .8 inches) was significantly greater than the control (6.4 in ­ches). No significant differences among treatments were Table 1_ The effects of thinning, fertil izing and root prun­ing in a 27-year-old, single-row green ash field windbreak on the yields of the corn cul t ivar 'Garst 8939' at a single site near Absaraka, N_D.1 Test Hundred Average Yield/Plot Weight Kernel Ear Treatment (bu/acre)2 (#/bu) Weight (gm) Length (in) Thinning 91.1 a3 56.9 a 18.9 a 6.8 a Fert ilizing 86.7 ab 56.3 a 19.3 a 6.5 ab Root Pruning 80.8 ab 56.1 a 18.7 a 6.5 ab Control 67.4 b 54.3 b 16.3 b 6.4 b 1	Non.signi ficant differences among treatments were fou nd for plants per acre, number of ears per plant , average ear diameter, kernel depth, kernel rows per ear, kernels per row, percent stem lodging, percent root lodging or percent ear drop. 21ndividual values in each column represent combined data across the four distances for each treatment. Composite yields were combined across the four treat­ments for each distance. Test weights compared in relation to the distance from the windbreak indicated sign ifican tly greater test weights for the plots immediately adjacent to the windbreak compared to weights taken 10 times farther from the windbreak , suggesting a beneficial effect from the trees (Table 2). Average ear length from plots harvested at the 10H distance was signficantly greater than the 1H distance (Table 2). Distance 5H produced the greatest number of kernels per ear followed by 10H and 2H . No significant dif­ferences among distances were detected for plants per acre, number of ears per plant , yield per plot, hundred kernel weight, average ear diameter, kernel depth, kernel rows per ear, kernels per row, percent stem lodging, percent root lodging, or percent ear drop. There were no significant treatment by distance interactions for any of the measured variables. Table 2. The effects of distance from a 27-year-old, single­row green ash field windbreak on the yields of the corn cul tivar 'Garst 8939' at a single site near Absaraka, N.D.1 Test Average Yield/Plot Weight Ear Kernels/ Distance (bu/acre)2 (#/bu) Length (In) Ear 1H 68.4 a3 56.7 a 6.2 b 497 b 2H 83.2 a 56.3 ab 6.5 ab 542 b 5H 9004 a 55.5 ab 6.8 a 608 a 10 H 84.0 a 55.1 b 6.8 a 598 ab 1Non.significant differences among treatments were found for plants per acre, number of ears per plant, average ear diameter, kerne l depth, kerne l rows per ear, kernels per row, percent stem lodging, percent root lodging or percent ear drop. 21 ndividual values in each column represent combined data across the four distances for each treatmen t. 3Column means followed by diffe re nt letters are signifi can tl y different at p ~ 0.05 based on Student·Newman·Kuels test. Potato Yield Potato yields ranged from 74 hundredweight per acre for the root pruning treatment to 57 hundredweight per acre for the thinning treatment (Table 3). There were no significant differences in yield among the three treatments and the con ­trol. Extreme soil variability coupled with erratic alkalinity levels throughout the site confounded the treatments, result ­ing in very irregular treatment effects. There was a signifi ­cant difference in yields among the four distances. Plots at IH had the lowest yield (45 hundredweight per acre), signif­icantly lower than the other three distances (66, 70 and 85 hundredweight per acre for distances 2H, 5H and 10H, re­spectively) (Table 4). Regression analysis identified a signif­icant relationship between plot yieid and distance from the windbreak, accounting for approximately 50 percent of the variability in yield. There were no significant treatment by distance interactions for yields per plot. 3Column means followed by di fferent letters are significantly different at p ~ 0.05 based on Student·Newman·Kuels test. 27 Table 3. The effects of thinning, fertilizing and root prun· ing in a 20-year-old, single-row Siberian elm field windbreak on the yields of the potato cultivar 'Monona' at a single site near Grand Forks, N.D. Treatment Root Thinning Fertilizing Pruning Control Yield/plot 1 57 a2 66a 74 a 69 a (hundredwe ight per acre) 1 Yield/plot represents combined data across the four distances for each treatment. 2Means fol lowed by the same letter are not sign ificantly different at P~0.05 based on Student·Newman·Kuel s test. Table 4. The effects of distance from a 20-year-old, single­row Siberian elm field windbreak on the yields of a potato cultivar 'Monona' at a single site near Grand Forks, N.D. Distance 1H 2H 5H 10H 2Yield/Plot 1 45 c 66 b 70 b 85 a (hundredweight per acre) 1 Yield/plot represents combined data across the four treatments at each distance. 2Means followed by different letters are significantly different at p~ 0.05 based on Student·Newman-Kuels test. DISCUSSION Field windbreaks had a large effect on yield expressed as plot differences at the various sampling distances away from the windbreak. The effect could not be generalized . For most variables measured in the corn study , the windbreak had no effect on yield . Some variables, however, displayed reduced yields adjacent to the windbreak while other vari­ables displayed enhanced yields adjacent to the windbreak. Favorable changes in microclimate associated with the prox­imity of the wi ndbreak may account for the enhanced yields (Bouchet et a I, 1963· Brown and Rosenberg, 1971; Kort, 1988). With other variables the greatest yields occurred near mid-fie ld. This may be a response to better snow and mois­ture distribution across the field caused by the windbreak (Scholten, 1988). The benefits of improved microclimate and better snow distribution are unique to field windbreaks as a conservation tool and were apparently unaffected by the applied management pra tices in 1989, the year prac­tices were implemented . The test windbreak management practices also influenced crop yields , particularly for those variables affected by wind­break proximity. Generally, the management treatments produced greater yie lds than did the controls. In the green ash windbreak, thinn ing produced the greatest yields. Thin­ning not only reduces tree to crop competition, it also im­proves snow and moisture distrubtion in subsequent years (Frank, 1979; Umland, 1979; Scholten, 1988), factors not present in the year of implementation. Of the three treat­ments applied to the green ash windbreak , root pruning typically produced the lowest yields. In the Siberian elm windbreak however, the root pruning treatment produced the highest yield, though not significantly different than the control. The extreme soil variability and irregular alkalinity levels associated with the Grand Forks site tended to con­foun d treatments, resulting in plot to plot variability within replications within treatments. Under improved circum­stances the root pruning treatment may prove to be the most beneficial treatment at the Grand Forks site, because Siber­ian elm has one of the most aggressive root systems of any windbreak species (Umland, 1979) . In 1990 , additional yield data will be collected from the field on the leeward side of the same two windbreaks . Sampling techniques to reduce soil variability will be used to !mprove the correlation between yield and management treatment or sampling distances from the windbreak. Mon­itoring crop yields on the leeward side of the windbreak should produce a greater yield difference between the thin­ned treatment and the other treatments, especially in years with normal snowfall, when thinning and branch elevation should allow more uniform distribution of snow loads across the field. Single-row field windbreaks are perennial tree plantings which provide an aspect of soil protection unavailable from other conservation methods. Field windbreaks generally produce an overall increased yield (Kort, 1988) , yet they can compete with adjacent crops to reduce yields. Prelimin­ary results from this study examining two field windbreaks indicate that windbreak management practices such as thin­ning and root pruning may minimize these compe itive ef­fects without jeopardizing the unique conservation aspects of field windbreaks. REFERENCES Bo uchet, R. J . , S . DeParcevaus and A Aroox . 1963. Improving crop yield by decreasing potential evapotranspiration. Ann is . Agron . 14:825-833. Brown , K.W. and N.J. Rosenberg . 1971. Turbulent transport and energy balance as affected by a windbreak in an irrigated sugar beet field. Agron . J . 63:351-355. Frank, AB. 1979. Crown pruning Single-row field windbreaks. Great Plains Ag. Coun. Pub . 9 2:113-119. Frank , AB., D.G . Harris and W.O. Willis . 1974. Windbreak influ­ence on water relations , growth and yield of soybeans . Crop Sci. 14:761-765. Greb , B.W . and A.~. Black . 1961. Effects of windbreak plantings on adjacent crops. J. Soil and Water Conserv. 16 (5) :223-227 . Kort, J . 1988. Benefits of windbreaks to field and forage crops. Agric . Ecosystems Enviro n. 22 :23: 165- 190. Scholten, H. 1988. Snow distribution on crop fields. Agric. Ecosys­tems Environ. 22/23:363-380 . Umland, E .R . 1979. Root pruning as a management technique . Great Plains Ag . Coun. Pub!. 92: 10 7-111. Zohar , Y .E . andJ .R. Brandle . 1978. Shelter effects on growth a nd yield of corn in Nebraska . La-Yaaran 28:11-19 . 28 

Field Windbreak Management and Its Effect on Adjacent Crop Yield

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