Bowden, Robert L.

Rooney, W. L.

Shroyer, James P.

Thompson, Curtis R.

Kansas State University

Kansas Agricultural Experiment Station Research Reports Volume 0 Issue 12 Keeping up with Research Article 69 1974 Interseeding Alfalfa into Declining Alfalfa Stands W. L. Rooney James P. Shroyer Robert L. Bowden See next page for additional authors This report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright 1974 Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. K-State Research and Extension is an equal opportunity provider and employer. Follow this and additional works at: https://newprairiepress.org/kaesrr Recommended Citation Rooney, W. L.; Shroyer, James P.; Bowden, Robert L.; and Thompson, Curtis R. (1974) "Interseeding Alfalfa into Declining Alfalfa Stands," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 12. https://doi.org/10.4148/2378-5977.7306 Interseeding Alfalfa into Declining Alfalfa Stands Keywords Keeping up with research; 3 (April 1974); Kansas Agricultural Experiment Station contribution; no. 34; Alfalfa; Interseeding; Autotoxicity; Declining Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. Authors W. L. Rooney, James P. Shroyer, Robert L. Bowden, and Curtis R. Thompson This research report is available in Kansas Agricultural Experiment Station Research Reports: https://newprairiepress.org/kaesrr/vol0/iss12/69 INTERSEEDING ALFALFA INTODECLINING ALFALFA STANDSW.L. Rooney, J.P. Shroyer,R.L. Bowden, and C.R. ThompsonlProducers have attempted to thicken declining alfalfastands by interseeding alfalfa into them, often with little orno success. This lack of success is due to a variety of factors,including autotoxicity; water stress; and disease, weed, andinsect pressures. Mature alfalfa plants produce compoundsthat inhibit the germination and growth of seedling alfalfa(autotoxicity). Established alfalfa also provides an environ-ment for pests and diseases that can harm alfalfa seedlings.If water becomes limiting, the seedlings are unable to com-pete with established alfalfa. For these reasons, researchershave concluded that interseeding alfalfa into existing standsoften will not succeed.Because of the difficulties in establishing a new alfalfastand in Kansas, considerable interest in interseedingremains. In recent years, this interest has increased becauseof reports in several farm magazines that the practice couldbe successful if high rates of fungicide were used to controlseedling disease. Our objectives were (1) to test the feasibil-ity of seeding alfalfa into established alfalfa stands in Kansasand (2) to determine if high rates of fungicide had any effecton seedling establishment in declining stands.This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.ProceduresSix on-farm locations were selected, three in northeastKansas and three in southwest Kansas. At each site, thestand of alfalfa had declined to a point where the producerwas considering destroying it and establishing a new stand.The experimental design was a randomized complete blockwith four replications, and a commercially available alfalfacultivar was seeded at a rate of 12 lb\acre. Experimental plotsize varied but was not less than 10 ft x 60 ft.Northeast Kansas Tests. The three sites used werelocated in Riley County and were nonirrigated. Each locationincluded untreated plots and applications of the recom-mended rate and twice the recommended rate of Apron seedfungicide. Plots were planted on April 1, 1994 using analfalfa no-till drill with 7-inch row spacing. At the time ofplanting, the existing stand was in an early vegetative growthstage (<15 cm tall and no buds). Within each replication,seedling and existing plant stands were counted in five ran-domly selected sample sites approximately 10 ft apart withina replication. At each sample site, existing stand counts(number of crowns/ft2) were taken for a 2 ft2 area, andseedling counts (number of seedlings\ft2) were taken for a1 ft2 area within the area counted for existing stand.Seedlings and existing stands were counted on April 22, fol-lowed by a second seedling count on May 13. Final countsof, existing stands and seedlings were taken on July 13 atonly one location.Southwest Kansas Tests. Interseeding trials wereconducted in Gray, Haskell, and Clark counties. The Grayand Haskell County trials were irrigated; the Clark Countytrial was nonirrigated. Each location included untreated plotsand applications of the recommended rates of Apron. Plotswere planted on April 8, 1994 using a drill with 2-inch rowspacings. At the time of planting, the existing stand was inan early vegetative growth stage (<15 cm tall and no buds).Sampling sites were selected using the same methodologydescribed above. At each sample site, existing stand countswere taken for a 10.5 ft2 area, and seedling counts weretaken for a 1 ft2 area within the existing-stand count area.Seedlings and existing stands were counted on April 20, May2, and May 10 for the Gray, Haskell, and Clark County trials,respectively. The Clark County location was lost because ofdrought stress, but second seedling counts at the Gray andHaskell County locations were taken on June 23 and 24.Analysis. Within each region, the effects of location andfungicide treatment on seedling emergence and survival weretested. Significant differences among treatment means weredetected using Fisher’s protected L.S.D. Regression analysiswas used to determine if seedling survival was affected byexisting stand density. The initial seedling count, secondThis publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.Table 1. Effects of location and fungicide treatment on alfalfa stand count means innortheast Kansas field trials.Existing Stand Seedling Stand Seedling StandLocation April 22 April 22 May 13plants/ft2Central Riley County 2.1 15.0 8.2Western Riley County 1.7 14.1 10.3Northern Riley County 2.3 15.9 6.5L.S.D. (P< .05) .4 n.s. 1.3Fungicide Treatment2 x Recommended Rate–Apron 2.1 15.5 8.9Recommended Rate–Apron 2.0 14.8 8.3Untreated 2.1 14.9 7.9L.S.D. (P< .05) n.s. n.s. n.s.Table 2. Effects of location and fungicide treatment on alfalfa stand count meansin southwest Kansas field trials.Existing Stand Seedling Stand Seedling StandLocation April/May* April/May* June 23/24plants/ft2Haskell County 1.4 7.6 1.3Gray County 1.0 19.3 4.2Clark County 1.2 11.3 —**L.S.D. (P < .05) .3 4.0 1.4Fungicide TreatmentRecommended Rate–Apron 1.2 11.6 1.8Untreated 1.2 13.9 1.9L.S.D. (P< .05) n.s. n.s. n.s.* Haskell County, May 2; Gray County, April 20; Clark County, May 10.** Stand failed because of drought and was removed from the study.seedling count, and the proportion of seedlings survivingwere regressed independently against existing stand densityfor each location.ResultsNortheast Kansas Tests. All three locations receivedadequate rainfall to successfully establish an alfalfa stand.Emergence at all locations was good. Seedling location(relative to existing alfalfa plants) seemed to have little effecton germination. In fact, some seedlings germinated directlynext to existing plants. Combined analysis indicated no sta-tistical difference between locations or fungicide treatmentsfor the April 22 seedling stand counts (Table 1). Analysis ofthe May 13 seedling stand counts indicated that statisticaldifferences existed between locations, but no significant dif-ferences were observed for fungicide treatments (Table 1).Regression analysis indicated no correlation between April22 seedling stand counts and the existing stand density.However, strong negative correlations were observedbetween May 13 counts of seedling stands and existingstands. The proportion of seedlings surviving from the firstto second counts was correlated negatively with existingstand as well (Fig. 1). The same trend was observed in theJuly counts of seedling stands and existing stand densities atone location (Fig. 1).Southwest Kansas Tests. Environmental conditionshad significant effects on seedling stands at two of the threelocations. In the nonirrigated Clark County trial, initial ger-mination was good, but drought killed the seedlings. At theHaskell County site, heavy weed pressure (kochia and grass)reduced initial and subsequent seedling densities, whichbiased the effects of the existing stand. Combined analysesof the three locations indicated significant differences inseedling density between locations, but fungicide treatmentsdid not affect seedling density (Table 2). Because of droughtand weed problems in the Clark and Haskell County trials,regression analysis for the western region was completedonly for the data from the Gray County trial. As wasThis publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.May 13, 1994Figure 1.July 13, 1994Regression of alfalfa seedling stand variablesagainst existing stand density for the centralRiley County location.observed in the northeast Kansas locations, no correlationwas detected between initial seedling stand and existingstand, but negative correlations were detected between theJune 23 counts of seedling stands and existing stands andbetween the proportion of surviving seedlings and the exist-ing stand.DiscussionIn two of six locations, alfalfa seedling establishment in anexisting stand failed for the same reasons that newlyestablished alfalfa stands fail. In the other four locations, anewly seeded stand would have been established successfullyin the absence of established alfalfa, whereas in the presenceof an existing stand, seedling mortality was quite high andseedling numbers were insufficient to replenish the existingstand.In all locations and on all seedling count dates, fungicidetreatments did not improve the survivability of alfalfaseedlings in an existing stand. Apron is a systemic fungicidethat is used to control early seedling diseases such asPythium and Phytopthora. Any benefit from seed treatmentswith Apron will be observed in the first 3 weeks after plant-ing. We saw no such benefits from treatments at any location.However, fungicide-treated seed is still recommended for anyalfalfa plantings to control seedling diseases.Although the data collected in this study could not beused to identify the specific cause of seedling death, diseaseand insect damage was evident on young seedlings. Symp-toms of autotoxicity also were observed in the trials.This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.Seedlings adjacent to existing plants were yellow and stuntedby the second count date. At the one location whereseedlings were counted on July 13, any surviving seedlingswere still stunted and small. Previous field and lab researchhas shown that autotoxicity can contribute to the decrease inseedling numbers and vigor.ConclusionsNone of the six alfalfa stands in this study wereinterseeded successfully to a satisfactory stand level. Clearly,fungicide seed treatments do not improve seedlingemergence or survival in established alfalfa stands. The sur-vivability of seedlings was correlated negatively with theexisting stand density. For every additional crown/ft2,seedling alfalfa survival was reduced by approximately 10%.Given that seedling counts were taken very early, furtherattrition could be expected as the season progressed, andthis was observed at the one northeast Kansas locationwhere seedling density was measured in July (Fig. 1) . There-fore, survival of any significant numbers of seedlings inexisting stands is highly unlikely. Although limited examplesof success with interseeding alfalfa into declining stands mayexist, the practice is likely to fail and is not recommended inKansas.lAlfalfa Geneticist, Dept. of Agronomy; Extension CropsSpecialist, Dept. of Agronomy; Extension Plant Pathologist,Dept. of Plant Pathology, Kansas State University, Manhat-tan; and Extension Crops and Soils Specialist, SW KansasResearch-Extension Center, Garden City, respectively.Trade names are used to identify products. Noendorsement is intended, nor is any criticism implied ofsimilar products not named. Products or product useswithout label registration are mentioned for informationalpurposes only and not as recommendations.Contribution no. 95-451-S from the KAES.This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.

Interseeding Alfalfa into Declining Alfalfa Stands (1995)

https://newprairiepress.org/cgi/viewcontent.cgi?article=7306&amp;context=kaesrr

Interseeding Alfalfa into Declining Alfalfa Stands (1974)

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