Corn (Zea mays L.) Production in a Grass/CIover Living Mulch System by Philip R Greyson Submitted in partial fùlfillment of the requirements for the degree of Master of Science at Nova Scotia Agricultural College Truro, Nova Scotia, in cooperation with Dalhousie University Halifax, Nova Scotia March, 1998 OCopyright by Philip R. Greyson 1998 National Library Bibiiothèque nationale du Canada Acquisions and Acquisitions et Bibliographie Services services bibliographiques The author has granted a non- L'auteur a accordé une licence non exclusive licence dlowing the exc1usive permettant à la National Libmy of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de rnicrofiche/film, de reproduction sur papier ou sur format électronique. 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TABLE OF CONTENTS TABLE OF CONTENTS LIST OF TABLES vii LIST OF FIGURES LIST OF ABBREVIATIONS xi ABSTRACT xii .- - ACKNOWEDGMENTS xii1 BJTRODUCTION 1 LITERATURE REVIEW 2.1 Corn 2.2 Living Mulches 2.2.1 Mulch suppression 2.2.1.I Chernical suppression 2.2.1.2Mechanical suppression 2.2.1.3 Combined mechanical and chernical suppression 2.3 Soil Physical Properties 2.3.1 Soil moisture 2.3 -2 Soi1 temperature 2.3.3 Soil nitrogen response OBJECTIVES METHODOLOGY 4.1 Background and Experimentai Design 4.2 Treatment Factors 4.2.1 Living mulch treatments 4.2.2 Control treatments 4.2.3 Nitrogen treatments 4.2.4 Imgation treatments 4.2.5 Straw mulch treatments 4.3 Field Preparation and Sampling 4.3.1 1995 Protocol 4.3.2 1996 Protocol 4.4 Statisticai Analysis 4.4.1 Yield and mulch analysis 4.4.2 Irrigation andysis 4.4.3 Frost analysis 4.5 Meteorological Conditions RESULTS 5.1 Corn Yields and Harvest Index 5.2 Imgation 5.3 Corn Growth Parameters 5 -4 Living Mulch 5.4.1 Mulch totals (between-row) 5.4.2 Mulch totals (within-row) 5.4.3 Living mulch composition 5.5 Frost Effects 5.6 Soil Moisture DISCUSSION 6.1 Corn Yields 6.2 Nitrogen Effects 6.3 Imgation 6.4 Soil Moisture 6.5 Frost 6.6 Straw Mulch 6.7 Methodology Improvements 6-7Conclusions LITERATURE CITED LIST OF TABLES Table 1 Summary of treatrnent combinations including treatment designation, nitrogen rate and mulch suppression description Table 2 Schedule of irrigation and average amount of irrigation water (L) applied to CONTROL and TILWHERB treatments in 1995 and 1996 Table 3 Surnrnary of field activities for 1995 and 1996 Table 4 Average total corn yield (kg DM ha-') and harvest index (HI) for 1995 and 1996 as affected by mulch suppression and nitrogen (N"). 39 Table 5 Total corn yield (kg DM ha-') averaged over rnulch suppression treatments in 1995 and 1996 under imgated and rainfed conditions. 40 Table 6 Final corn heights and number of days £tom seeding to silking for 1995 and 1996 as affected by mulch suppression and nitrogen (N). 4 1 Table 7 Between-row mulch dry matter (kg DM ha-' ) on five sampling dates as afEected by mulch suppression and nitrogen (IV) in 1995. Table 8 Between-row mulch dry matter (kg DM ha-' ) on four sampling dates as affected by mulch suppression and nitrogen (N) in 1996 Table 9 Within-row mulch dry matter (kg DM ha" ) on five sarnpling dates as afEected by mulch suppression and nitrogen (N) in 1995. Table 10 Within-row dry mattw(kg DM ha-' ) on four sampling dates as af5ected by mulch suppression and nitrogen (N) in 1996. Table 1 1 Mulch composition (%) on two sampling dates as affected by mulch suppression and nitrogen (N) in 1995. Table 12 Mulch composition (%) on four sampling dates as afTected by mulch suppression and nitrogen (N) in 1996. Table 13 Frost damage scores as affected by mulch suppression and nitrogen (N) for the fiost event on June 22, 1996. vii Table 14 Soi1 resistance to penetration (bars) under mulch and no mulch (CON'TROL) in October 1996. LIST OF FIGURES Figure 1 Layout of expenmental plots in the Brookside field in 1995 and 1996 (See Table 1 for treatrnent definitions.). Experimentai units are 8 rn X 3.1 m. Figure 2 Average May-September mont hly precipitation (mm) for 1995 and 1996 in Brookside, N.S. compared to 30 normal. Figure 3 Daily maximum temperatures fiom seeding to first Auturnn fiost in 1995 for Brookside, N.S. Figure 4 Daily minimum temperatures from seeding to first Autumn fiost in 1995 for Brookside, N. S. Figure 5 Daily precipitation fiom seeding to first Auturnn frost in 1995 for Brookside, N. S. Figure 6 Daily maximum temperatures from seeding to first Autumn fiost in 1996 for Brookside, N.S. Figure 7 Daily minimum temperatures fiom seeding to first Autumn frost in 1996 for Brookside, N.S. and showing the fiost event of June 22. Figure 8 Daily precipitation fiom seeding to first Auturnn frost in 1996 for Brookside, N. S. Figure 9 Corn development for mulch and no-mulch treatments in 1995 as afEected by heat unit accumulation. Error bars are equal to + 2 S.E. Figure 10 Corn development for mulch and no-mulch treatments in 1996 as afEected by heat unit accumulation. Error bars are equal to t 2 S.E. Figure 1 1 Volumetric soil moisture (0-1 5 cm soil depth) under mulch and conventional tillage measured during the 1996 growing season. Figure 12 Volumetric soil moisture ( 15-25 cm soil depth) under mulch and conventional tillage measured during the 1996 growing season. Figure 13 Volumetnc soil moisture (50 cm soil depth) under mulch and conventional tillage measured during the 1996 growing season. 5 1 LIST OF ABBREVIATIONS AWC available water capacity CD calendar day CHU con heat unit DM dry weight of four harvested plants (kg) DMK kemel dry matter (kg) DMWP whole plant dry matter (kg) FC field capacity FDS fiost damage score HI harvest index HRL harvested row length (m) LA leaf area (m) LAI leaf area index L& incoming longwave radiation LT reflected longwave radiation N nitrogen -03 ammonium nitrate m3 amrnonia PDM proportion dry matter PW proportion of minimally damaged plants pMOD proportion of moderately damaged plants pSEV proportion of severely damaged plants PWP permanent wilting point RCBD randornized complete block design RW row width (0.76in) SM soi1 moisture s3c incoming shortwave radiation ST reflected shortwave radiation TDR time domain reflectometry wwt wet weight of four plants ww2 wet weight of plants in harvested area Treatment factors TILL tillage treatment consisting of a 30 cm wide tilled stnp HERB herbicide treatment consisting of a 30 cm wide herbicide application TILL/HERB combination of a 30 cm wide tilled strip and a 30 cm wide herbicide band CONTROL conventionai tillage and weed control STRAW treatment with a straw mulch placed over the living mulch Abstract Living mulches are low growing swards of vegetation that are used to reduce soil erosion, to conserve soil moisture, and to control weeds when grown with row crops. They may, however, also compete with the pnmary crop for light, nutnents and water. Therefore they muR be suppressed so that the pnmary crop is not severely affected. They have been used primarily in vegetable crop production, but numerous attempts have been made to use them with field crops such as maize and wheat. The current study examined the effects of difTerent methods of mulch suppression on silage corn (Zra muys L.) in Truro, N.S. during 1995 and 1996. Silage corn was grown in a living mulch composed of white clover (Tnfoiizm repens L.) and mixed grasses. The mulch was suppressed with herbicide bands (giyphosate and atrazine), tilled strips, or a combination of both. Corn was planted into the suppressed strips and the mulch in between the rows was mowed early in the season to reduce competition. Control plots with conventional tillage and herbicide use (no rnulch) were also planted. Where both methods of suppression were used on the mulch, corn yields were not significantly different (p>0.05) fiom yields in the unmulched control plots in 1995, but were reduced by 40% in 1996. Where only one method of mulch suppression was used (either mechanical or chemical) corn yields in plots with living mulch were reduced by 39 to 72% compared to the unmulched control plots. Yields in the mulched plots were 27 % lower in the second year of the study than in the first year. This reduction rnay have been due to the efects of a fiost in late June of 1996 which caused signifiant damage to corn in the mulched plots, but little darnage in the unmulched plots. Higher soi1 moisture levels in the mulched plots may have caused lower soil temperatures, which in turn made the corn in the mulched plots prone to fiost damage. In addition to the increased risk of frost damage, the living mulch also delayed corn emergence and development. While there may be some reductions in herbicide use with living mulch, the nsk in cool temperate climates of delayed development and reductions in yield rnay Iimit the use of living mulches to cool season crops. Acknowledgments 1 would like to thank a number of individuah and organizations for support given to me during the course of this projea.