Development of Annual Medics as living mulches for Commercial Pumpkin
Production.
Principal Investigator:
Richard M. Riedel, Plant Pathology Dept., Ohio State University
Christian A. Wyenandt, Plant Pathology Dept., Ohio State University
Introduction:
Cover crops are used in high-input agronomic and vegetable production systems to reduce soil erosion, fungicide use, plant disease, and weeds. Cover crops have also been shown to increase soil organic matter, nitrogen availability, and moisture. Traditional cover crops, such as hairy vetch (Vicia villosa) and winter rye (Secale cereale), widely used in tomato production have been used in pumpkin production with limited success. Traditional fall-sown cover crops, such as hairy vetch and winter rye, are typically killed by herbicide applications, mowing, and mechanical undercutting prior to spring planting. Pumpkin growers in Ohio have asked for alternative cover crops that could be spring or fall-sown and require less input than the traditional cover crops. Annual medics (Medicago spp.), native to Australia, have been studied as forage crops in the upper Midwest. Annual medics with their less invasive, dense, low growth habits and drought tolerance make them potential candidates as spring-sown living cover crops or fall-sown winter-killed cover crops in pumpkin production.
Objectives:
1. Selection of annual medics as living mulches with horticultural qualities suitable for use as cover crops for commercial pumpkin production.
Materials and Methods:
Plots in a randomized complete block design with 14 treatments (4 reps) were set up at two research farms in Columbus and Piketon, OH. The treatments included: no cover (control), rye, rye + hairy vetch, oat, oat + vetch, vetch, snail medic, burr medic, barrel medic, medic mix, 2 non-dormant alfalfas (Pioneer 5929 and WL711), medic + oat, and medic + vetch. Late May and early September seeding of 10' x 20' plots were done with a walk behind drill seeder and a hand-held broadcast seeder, respectively. Broadcasted seed was lightly incorporated with a rake. Since very little information is available spring seeded treatments included a high and low seeding rate for each. Spring high and low seeding rates were as follows: control, oat (90 and 60 lbs/A), oat + hairy vetch (50 lbs each/A and 25 lbs each/A), rye (90 lbs/A and 60 lbs/A), rye + hairy vetch (50 lbs each/A and 25 lbs each/A), hairy vetch (50 lbs/A and 30 lbs/A), snail medic (30 lbs/a and 20 lbs/A), burr medic (20 lbs/A and 12 lbs/A), non-dormant perennial alfalfa (WL711) (30 lbs/A and 20 lbs/A), non-dormant perennial alfalfa (Pioneer 5929) (30 lbs/A and 20 Lbs/A), medic mix (20 lbs each/A and 15 lbs each/A), medic + oat (25 lbs/A and 70 lbs/A), medic + oat (12.5 lbs/A and 40 lbs/A), medic + rye (25 lbs/A and 70 lbs/A), and medic + rye (12.5 lbs/A and 40 lbs/A). Cover crop height was measured at 3 and 6 weeks after spring planting to determine growth rates (table 1.1).
Results and Discussion:
Due to a very hot and dry summer cover crop growth was slow and weed pressure very high. A mid-July application of 2,4-DB @ 3 pts/A reduced weed populations as well as killed the rye, rye + vetch treatments. Due to the weed populations and lack of cover crop growth all spring-seeded treatments were mowed down. Interestingly, the Medicago spp. were unaffected by the herbicide application. This suggests that annual medics could be used in conjunction with an early 2,4-DB application (probably 2-3 weeks after cover crop seeding) and still act as a living cover crop if weed pressure is potentionally high. Weed control could then be obtained without having an effect on June pumpkin plantings. Observational data indicates medics may exhibit better growth potential under cooler temperatures. All low seeding rates for fall of 1999 were dropped because observational data suggested rates were much to low to produce adequate biomass and compete with weed pressure. Seeding rates were increased in some fall treatments for the same reasons (table 1.2). Fall-seeded cover crop treatments established much quicker and more uniformly than spring-seeded treatments. This was most likely due to reduced weed competition and cooler temperatures. Data from our preliminary study suggests that spring and fall-sown cover crops may be successfully incorporated in commercial pumpkin production. Fall cover crop treatments look very promising and new spring-sown cover crop plots will be established this coming April. Cover crop biomass will be collected from fall (1999) and spring-seeded (2000) cover crop treatments this summer at pumpkin planting and this fall at harvest. This data will give us a better understanding which of the fall and spring-sown cover crops are able to produce an adequate amount of biomass to last the entire pumpkin production season. The pumpkin cv. 'Magic Lantern' , a compact, bush-type variety will be seeded in cover crop treatments this summer and should give us a better understanding on how cover crops will affect soil water / plant relations, fruit quality, and fruit disease development.
Table 1.1 Seeding rates and cover crop heights at 3 and 6 weeks after planting (WAP) of
spring-sown cover crops in 1999 at Waterman Horticultural and Natural
Resources Laboratory, Columbus, OH.
| Height | Height |
| (cm) | (cm) |
| Scientific Names | Seeding Rate (lbs/A) | 3 WAP | 6 WAP |
| Control | none | |
| Avena sativa |
90 |
2.8 |
7.2 |
| Avena sativa / Vicia villosa |
50 & 50 |
2.4 / 1.6 |
7.2 / 2.8 |
| Secale cereale 'Amor' / Vicia villosa |
50 & 50 |
2.2 / 1.5 |
2.8 / 2.0 |
| Vicia villosa |
50 |
1.8 |
2.4 |
| Medicago scutellata - Snail Medic |
30 |
1.2 |
3.2 |
| Medicago polymorpha - Burr Medic |
20 |
0.8 |
2.4 |
| Medicago truncalata - Barrel Medic |
20 |
0.84 |
1.6 |
| Medicago sativa Pioneer 5929 |
30 |
1.5 |
2.6 |
| Medicago sativa 'WL711' |
30 |
1.5 |
2.8 |
| M. scutellata, polymorpha, truncalata |
20 |
~1.0 |
~2.0 |
| M. scutellata / Avena sativa |
25 & 70 |
1.1 / 2.6 |
2.8 / 8.0 |
| Secale cereale 'Amor' |
90 |
2.3 |
3.6 |
| M. scutellata / Secale cereale |
25 & 70 |
1.1 / 2.5 |
2.4 / 3.2 |
Table 1.2 Cover crop seeding rates for fall of 1999 at Waterman Horticulture and
Natural Resources Laboratory, Columbus, OH.
| Treatment | Scientific Names | lb/A |
| UTC |
| none |
| Oat |
Avena sativa |
90 |
| Oat/Vetch |
Avena sativa / Vicia villosa |
50 & 50 |
| Rye/Vetch |
Secale cereale 'Amor' / Vicia villosa |
50 & 50 |
| Vetch |
Vicia villosa |
50 |
| Medic- Snail |
Medicago scutellata |
50 |
| Medic -Burr |
Medicago polymorpha |
40 |
| Medic - barrel |
Medicago truncalata |
40 |
| ND Alfalfa |
Medicago sativa Pioneer 5929 |
40 |
| ND Alfalfa |
Medicago sativa 'WL711' |
40 |
| 3 Medics |
M. scutellata, polymorpha, truncalata |
20 ea. |
| Medic/Oat |
M. scutellata / Avena sativa |
40 & 70 |
| Rye |
Secale cereale 'Amor' |
90 |
| Medic/Rye |
M. scutellata / Secale cereale |
40 & 70 |
For further information contact Richard M. Riedel , Professor, Dept. of Horticulture & Crop Science, The Ohio State University or the Ohio IPM Office.
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