Publication 360, Fruit Production Recommendations: Cover Crops

Excerpt from Publication 360, Fruit Production Recommendations 2010-11,
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Table of Contents

1. Introduction
2. Grasses
   • Spring cereals
   • Winter cereals
   • Warm season grasses
3. Legumes
4. Non-legume broadleaves
5. New and emerging cover crops
• Table 3-17. Selecting a Cover Crop (PDF 70 kb)
• Table 3-18. Characteristics of Cover Crops (PDF 83 kb)
6. Other topics in Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops
   • Assessing Nutrient Needs
   • Soil Organic Matter
   • Soil pH and Liming
   • Nitrogen
   • Phosphorus
   • Potassium
   • Calcium
   • Magnesium
   • Micronutrients
7. Ch. 3, Soil Management, Fertilizer Use, Crop Nutrition & Cover Crops - PDF 189 kb
8. Related Links

Introduction

Cover crops play a major role in soil management by providing ground cover to reduce erosion and by adding organic matter to improve or maintain the soil. Plant cover crops immediately after harvest to get the most benefit from the cover crop investment. While broadcast application and incorporation of cover crop seed works well to establish cover crops, direct seeding or drilling will ensure faster and more even establishment.

Knowing what you want to achieve with a cover crop will help you select the best one for the job. See Table 3-17. Selecting a Cover Crop, below and Table 3-18. Characteristics of Cover Crops, below. Cover crops can be divided into three groups based upon plant types: grasses, legumes and non-legume broadleaves.


Grasses

Grasses have fine, fibrous root systems that are well suited to holding soil in place and improving soil structure. Grass species suitable for cover crops are fast growing and relatively easy to kill (either chemically, mechanically or by winter temperatures). Grasses do not fix nitrogen from the atmosphere, but they can scavenge large quantities of residual nitrogen left in the field after harvest. Wind strips are usually created from overwintering grass cover crops.


Spring cereals

Spring cereals are well suited for late summer and early fall plantings. Under good growing conditions, spring cereals produce the greatest amount of crop biomass, and provide good ground cover. Once well established, spring cereals are relatively tolerant of frost. Do not attempt to establish spring cereals late in the fall however, as the growth will be limited.


Winter cereals

Winter cereals are highly versatile cover crops. They can be planted in summer and will tiller and thicken due to their need for a cold treatment before flowering. They can also be planted in fall for soil cover. Winter cereals generally overwinter well providing winter and spring erosion protection. These grasses can be used to create spring wind barriers or residue mulch, or they can be killed early with herbicide to minimize residue cover at planting.


Warm season grasses

Warm season grasses like sorghum and millet are best suited for planting into the warmer soils of late June, July and early August. They are very sensitive to frost. Root growth is extensive and the top growth lush. Be prepared to mow these grasses to keep stalks tender and prevent heading. Do not mow closer than 15 cm to ensure regrowth. Some nitrogen may need to be applied to achieve optimal growth.


Legumes

Legume cover crops can fix nitrogen from the air. They then supply it to the succeeding crop, as well as protecting the soil from erosion and adding organic matter. The amount of nitrogen fixed varies between species. Generally, more top growth indicates that more nitrogen is fixed. Ontario research has suggested that legume cover crops, such as red clover, are also effective at scavenging residual nitrogen from the soil.

Nitrogen release from legumes can be inconsistent. Account for this when calculating crop fertilizer needs. Excess nitrogen release late in the season could lead to excessive vegetative growth in fruit crops.

Some legume species, such as alfalfa or red clover, have aggressive tap roots that can break up subsoil compaction, but this requires more than one season's growth.


Non-legume broadleaves

These broadleaf crops cannot fix nitrogen out of the air but they may absorb large quantities from the soil. Growth will be poor if soil nitrogen levels are low or if compaction is severe. These crops are not winter-hardy, so additional control measures are not normally required. Do not allow these crops to go to seed, as the volunteer seedlings can become a significant weed problem.

New and emerging cover crops

Every year new crops are evaluated as cover crops. Often these species are from different parts of the globe and may not be well adapted to Ontario growing conditions. For more information on new and well known cover crop species, see the soil management section of the OMAFRA website or look at the regional pages from the Midwest Cover Crop Council.

Table 3-17. Selecting a Cover Crop (PDF 70 kb)


Function of the Cover Crop	Best Choice for Cover Crop
Nitrogen production	Red clover or vetch
Nitrogen scavenging	Fall uptake - oilseed radish and other brassicas, oats Winter/spring uptake - rye, winter wheat
Weed suppression	Oilseed radish and other brassicas, winter rye Buckwheat
Nematode suppression1	Cutlass mustard Sudans/sorghums - Sordan 79, Trudan 8 Pearl millet - CFPM 101 Marigold - Crackerjack, Creole Oilseed radish - Adagio, Colonel
Soil structure building	Oats, overwintered winter rye
Compaction elimination	Alfalfa, sweet clover
Biomass return to soil	Fall - oats, oilseed radish Summer - millets, sorghum, sudan
Erosion protection (wind or water)	Winter rye, winter wheat, ryegrass (well established)

¹ Nematode suppression is specific to the variety of cover crop and the species of nematode.

Table 3-18. Characteristics of Cover Crops (PDF 83 kb)
Table 3-18a. Grasses
| Broadleaf Legumes | Non-legume Broadleaf |

Grasses	Spring cereals	Winter wheat	Winter rye	Sorghum sudan	Pearl millet	Ryegrass
Seeding Rate kg/ha1	100-125	100-130	100-125	50	4	12-18
Seeding Time	Mid-Aug-Sept	Sept-Oct	Sept-Oct	Jun-Aug	Jun-Aug	Apr-May or Aug-early Sept
Min. Germination Temp. C (F)	9 (48)	3 (38)	1 (34)	18 (65)	18 (65)	4.5 (40)
Nitrogen: Fixed (F) or Scavenged (S)2	S	S	S	S	S	S
Overwintering Characteristics	killed by heavy frost	overwinters very well	overwinters very well	killed by frost	killed by frost	annual, Italian partially survive; perennial over-winters
Building Soil Structure	good	good	very good	good	good	very good
Weed Suppression	good	good	very good	good/fair	good/fair	fair/poor
Nematode Rating3 Lesion/rootknot	+/-	+/nh	+4/nh	nh3/-	nh3/nh3	-/-
Growth Rate	very fast	fast	very fast	very fast	fast	slow establishment
Root Type	fibrous	fibrous	fibrous	coarse fibrous	coarse fibrous	fibrous

 

Table 3-18b. Broadleaf Legumes
| Grasses | Non-legume Broadleaf |

Broadleaf Legumes	Hairy vetch	Red clover	Sweet clover	Soybeans	Field Peas
Seeding Rate kg/ha1	20-30	8-10	8-10	40-50	40-100
Seeding Time	Aug	Mar-Apr	Mar-Apr	Aug	Jul-early Sept
Min. Germination Temp. C (F)	15.6 (60)	5 (41)	5.5 (42)	8 (46)	5 (41)
Nitrogen: Fixed (F) or Scavenged (S)2	F/S	F/S	F/S	F/S	F/S
Overwintering Characteristics	overwinters	overwinters	overwinters	killed by frost	killed by heavy frost
Building Soil Structure	good	good	good	poor	poor
Weed Suppression	fair/poor	fair	fair	good/fair	good/fair
Nematode Rating3 Lesion/rootknot	++/+	++/+++	-/-	+/+	-/-
Growth Rate	slow establishment	slow establishment	slow establishment	fast	fast
Root Type	tap with secondary fibrous	weak tap/ fibrous	strong tap	tap	weak tap/fibrous

 

Table 3-18c. Non-legume Broadleaf
| Grasses | Broadleaf Legumes |

Non-legume Broadleaf	Buckwheat	Oilseed Radish6	Other Brassicas6 i.e. mustard, forage radish
Seeding Rate kg/ha1	50-60	10-14	varies with spe-cies
Seeding Time	Jun-Aug	Mid-Aug-early Sept	Mid-Aug-early Sept
Min. Germination Temp. C (F)	10 (50)	7 (45)	5-7 (41-45)
Nitrogen: Fixed (F) or Scavenged (S)2	S	S	S
Overwintering Characteristics	killed by first frost	killed by heavy frost	species depend-ent, many killed by heavy frost
Building Soil Structure	poor	fair	fair
Weed Suppression	very good	very good	very good
Nematode Rating3 Lesion/rootknot	+++/nh	-3/-3	-3/-3
Growth Rate	fast	fast	fast
Root Type	weak tap/fibrous	moderate tap	moderate tap

Nematode Rating Codes: - = poor or non-host; + = ability to host; nh = non-hosts.
¹ 100 kg/ha = 90 lb/ac.
² Oilseed radish, buckwheat and the grasses do not fix nitrogen from the air but are scavengers of nitrogen from soil and manure applications.
³ Varietal differences in cover crop species may affect nematode reaction.
⁴ Rye whole season rating would be higher.
⁵ Some diseases caused by Pythium and Phytophthora can be more severe after legume cover cropping.
⁶ Oilseed radish and other Brassica crop residues can be toxic or allelopathic to subsequent crops if the following crop is planted too closely after incorporation of the cover crop. Allow the cover crop residues to break down or desiccate before planting the next crop.

Related Links

• OMAFRA Publication 611, Soil Fertility Handbook
• Soil Management
• Soil Fertility & Crop Nutrition
• Soil Water Management
• Best Management Practices: Soil Management
• Cover Crops
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 75: Guide To Weed Control