Growth and weed suppression ability of common and new cover crops in Germany

doi:10.1016/j.cropro.2014.04.022

Crop Protection

Volume 63, September 2014, Pages 1-8

https://doi.org/10.1016/j.cropro.2014.04.022 Get rights and content

Highlights

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We evaluate the growth and weed suppression ability of common and new cover crops.
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Cover crops need fast growth and soil coverage for superior weed suppression.
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Tartary buckwheat and forage radish are well suited as cover crops in Central Europe.
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Cover crop plots also show a reduced weed density in spring.

Abstract

Cover crops have a wide-ranging influence on the agroecosystem and create multiple benefits for farmers. A major benefit of cover crops is the suppression of weeds during fall and winter, which can help to reduce soil tillage and herbicide use. However, only a small number of cover crop species are currently grown in Germany. To enlarge this number, four new cover crop species including tartary buckwheat, forage radish, red oat and grain amaranth were tested in comparison with common cover crop species such as white mustard, oilseed radish and phacelia. Emergence, soil coverage, dry matter production and weed suppression ability was assessed for all cover crop species. White mustard emerged faster than all other cover crops and produced the highest amount of shoot dry matter at both locations in southwest Germany twelve weeks after planting (WAP). Oilseed radish was the only cover crop that reduced the weed dry matter in all experiments eight WAP. Phacelia was able to reduce weed density by 77% at Meiereihof twelve WAP. Tartary buckwheat offered the highest soil coverage four WAP, produced the greatest shoot dry matter eight WAP and reduced weed dry matter by more than 96% at Meiereihof and Ihinger Hof twelve WAP. Forage radish produced the highest root dry matter and reduced spring weed density by more than 81% in all experiments. Red oat and grain amaranth emerged slowly, produced less biomass than other cover crops and did not suppress weed growth. The results show that tartary buckwheat and forage radish are well suited as new cover crops in Germany due to their fast growth and good weed suppression ability.

Introduction

Cover crops influence the agroecosystem in many positive ways. They protect the soil from wind and water erosion (Baets et al., 2011, Parlak and Parlak, 2010), capture, recycle and redistribute nutrients, especially nitrate (Hooker et al., 2008), increase the soil organic matter (Ding et al., 2006), reduce leaching of herbicides (Potter et al., 2007), provide a habitat for beneficial insects (Tillman et al., 2004), suppress weeds and volunteer crops and produce additional forage often resulting in higher yields of subsequent crops (Blanco-Canqui et al., 2012). Cover crops can suppress weeds and volunteer crops either by competition for light, water and nutrients or the release of allelopathic substances from living or decomposing plant tissue (Bezuidenhout et al., 2012, Creamer et al., 1996). For significant weed suppression, a rapid emergence, intensive soil coverage and dry matter production of cover crop are required (Brennan and Smith, 2005).

In the last decades, diversity of cover crop species in Germany has rather been low. White mustard (Sinapis alba L.) and oilseed radish (Raphanus sativus L. var. oleiferus) have been cultivated because of their high biomass production and capability of certain varieties to reduce the populations of phytopathological nematodes in crop rotations including sugar beets (Beta vulgaris L.) and potatoes (Solanum tuberosum L.) (Smith et al., 2004). They also decrease the risk of nitrate losses due to leaching (Wyland et al., 1996) and provide good weed control (Brennan and Smith, 2005). Phacelia (Phacelia tanacetifolia Benth.) is commonly grown as cover crop because it is not related to any main crop in Germany and hence not expected to be a host of important pests and crop diseases. Phacelia is mostly used in crop rotations including canola (Brassica napus L.). Phacelia also attracts bees and delivers nectar and is able to prevent nitrate leaching and suppress weed growth (Brant et al., 2009). Common cover crops require sufficient soil water, moderate temperatures and good seed-bed preparation for quick emergence and vigorous growth within the first few weeks after planting. However, growing conditions are often less favorable after harvest of annual grain crops. Therefore, new cover crop species are required that are more tolerant to unfavorable growing conditions such as drought and compacted soils but still guarantee vigorous growth in fall.

Among those potential new cover crops, tartary buckwheat (Fagopyrum tataricum L. Gaertn.) may be well suited for cultivation under short-term and unfavorable environmental conditions due to its fast emergence and strong growth within the first few weeks after planting. Tartary buckwheat is closely related to common buckwheat (Fagopyrum esculentum Moench) and shows similarities in its morphology and growth rate (Matsuura et al., 2005), however leaves of tartary buckwheat are arrow-shaped and shoots are more branched than of common buckwheat (Campbell, 1997). Buckwheat species are well known for their high competitive ability that enables them to suppress even perennial weeds (Bicksler and Masiunas, 2009). Another potential new cover crop species is forage radish (R. sativus L. var. longipinnatus), which has already been investigated as a summer annual cover crop in the Mid-Atlantic region of the USA (White and Weil, 2010). Forage radish is able to cover the soil surface completely within a few weeks after sowing and produces high shoot- and root dry matter that results in excellent weed suppression (Lawley et al., 2011). The third potential new cover crop for Germany is red oat (Avena byzantina K. Koch). Red oat is closely related to common oat (Avena sativa L.) and is cultivated especially in the south of Brazil for grain and forage production and as cover crop in no-tillage systems (Martinez et al., 2010). Until now, little is known about growth and weed suppressing ability of red oat as cover crop in Europe. Also cultivation of grain amaranth (Amaranthus cruentus L.) as cover crop has only been investigated in few studies before. Boer et al. (2008) and Mennan et al. (2009) found that grain amaranth produces equal dry matter to common cover crops in Turkey and Brazil.

The objective of this study was to evaluate the growth and weed suppression ability of common and new summer annual cover crops after harvest of cereal grains such as wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) to find new suitable cover crops for cultivation in Germany.

Section snippets

Experimental sites

Field experiments were conducted at the experimental stations Ihinger Hof (48°74′N, 8°92′E, 478 m altitude) in 2010 and 2011, Meiereihof (48°71′N, 9°21′E, 435 m altitude) in 2011 and Trossin (51°61′N, 12°81′E, 120 m altitude) in 2011. At Ihinger Hof and Meiereihof in the southwest of Germany, soil type was a Haplic Luvisol. Soil texture at Ihinger Hof was “Clay Loam” with a soil mineral nitrogen (N_min) content in topsoil before cover crop seeding of 18.1 kg ha⁻¹ in 2010 and 17.5 kg ha⁻¹ in

Weather conditions

In 2010, weather conditions were very similar to the long-term average in August, while from September until November weather was relatively cold and rainy. During the second year, weather was characterized by good growing conditions with high temperatures and sufficient soil water in fall at all locations. At Ihinger Hof and Meiereihof, temperatures in fall were 0.5 °C–2.4 °C above the long-term average. Especially September was characterized by warm and sunny weather with daily temperature

Cover crop emergence and soil coverage

There were only small differences in cover crop emergence among the experiments as a result of similar temperatures during the germination process. Temperature was the main factor influencing the required time for germination and emergence due to sufficient water availability at the time of sowing (Schneider and Gupta, 1985). The rapid emergence of Brassica species was also observed in former studies and seems mainly to be a result of fast water uptake due to a high surface to volume ratio of

Conclusions

White mustard and oilseed radish were the most promising common cover crops in this study to suppress weeds. Tartary buckwheat and forage radish were the most effective new cover crops in terms of weed control. Both species emerged relatively fast, covered the soil quickly and produced high amounts of shoot and root dry matter. Red oat and grain amaranth reduced weed growth only at one site and were less effective at the other location. Further research is required for a final estimation of

Acknowledgment

We thank the Saxon State Office for Environment, Agriculture and Geology (LfULG), especially Anja Schmidt for the great support at the experimental location Trossin. Thanks are also given to the field and laboratory personnel from the department of weed science and the experimental station Ihinger Hof. Furthermore, we gratefully acknowledge Katharina Anne Kesenheimer for her outstanding support during the realization of the experiments.

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View full text

Growth and weed suppression ability of common and new cover crops in Germany

Highlights

Abstract

Introduction

Section snippets

Experimental sites

Weather conditions

Cover crop emergence and soil coverage

Conclusions

Acknowledgment

Eur. J. Agron.

Geoderma

Field Crops Res.

Agric. Ecosyst. Environ.

Cover crops and their erosion-reducing effects during concentrated flow erosion

Catena

Very early detection of canopy presence by seeds through perception of subtle modifications in red:far red signals

Funct. Ecol.

Root and shoot competition intensity along a soil depth gradient

J. Ecol.

Cover crops of oats, stooling rye and three annual ryegrass cultivars influence maize and Cyperus esculentus growth

Weed Res.

Canada thistle (Cirsium arvense) suppression with buckwheat or sudangrass cover crops and mowing

Weed Technol.

Differential response of weed species to added nitrogen

Weed Sci.

Summer cover crops fix nitrogen, increase crop yield, and improve soil-crop relationships

Agron. J.

Biomass, decomposition and soil cover by residues of three plant species in central-western Brazil

Rev. Bras. Cienc. Solo

Competition of some summer catch crops and volunteer cereals in the areas with limited precipitation

Plant Soil Environ.

Winter cover crop growth and weed suppression on the central coast of California

Weed Technol.

Buckwheat. Fagopyrum esculentum Moench. Promoting the Conservation and Use of Underutilized and Neglected Crops

Mechanisms of weed suppression in cover crop-based production systems

Hortscience

Root mass for oilseed and pulse crops: growth and distribution in the soil profile

Can. J. Plant Sci.