Technical Notes French Beans

French Beans: Role of this Summer Legume in Conservation Planning

Rani G. Kumar, Girish K. Panicker* and Franklin O. Chukwuma French, Snap or Kidney beans, Phaseolus vulgaris L., are some of the oldest-cultivated vegetables. This annual, fast-growing legume originated in South and Central America and spread to other parts of the world through the Spanish. Fully matured French beans are called Kidney beans, and French beans with climbing nature are known as runner beans (other names include flageolets and haricot beans). Being sub-tropical in origin, they are susceptible to frost and require a sunny and sheltered site with 61-86°F, for ideal growth. French bean is one of the most important crops in the Unites States and ranks fifth in acreage and seventh in value among the primary vegetables.

Purposes    

To conserve soil and water through the use of vegetation To maintain and/or to improve soil availability, quality, and soil nutrients To suppress weeds, reduce insect pests and diseases, and increase crop yield To improve soil tilth, soil organic matter, and soil structure

Planting: Early prepared seedbed, time of planting, certified seeds, evenly moist soil enriched with compost or fertilizer with a pH of 5.5 to 7 are vital for bountiful returns. June or July is the suitable time to plant. French beans are usually dwarf varieties. Sow seeds 2 inches deep and drop a seed about every 2-4 inches, with 6 to 9 inches within rows and 24 to 36 inches between rows.

One inch of water per week is essential for pod development and flowering. The flowers are equipped with both female and male organs and self-pollinating or can be pollinated by bees.

Harvest: Pods are ready to harvest within 45 days (dwarf varieties) to 70 days (climbing varieties) after planting. Pods should be regularly picked while tender and young to boost yield, and prolong flowering and harvest. Take precaution against Halo Blight disease during French Beans harvest. Remove only the top portion of the plant and leave the roots in the ground to decay and release nitrogen. Only fully matured beans are harvested for seed. The average yield recorded in a heavy soil is 11,500 lbs/acre.

2 Soil: French beans grow in a variety of soils but best results can be obtained with a minimum soil temperature of 60°F, weed free, well-drained, light sandy, medium loamy, heavy clay, neutral or slightly acidic soils, and consistent moisture. Alkali and salty spots should be avoided. In sandy soils, beans mature in shorter time than on heavier soils. Preparation of the soil before sowing with organic manure, leaf-mould etc. will improve fertility, retain moisture, and result in high yields. As a legume with deep-rooted nitrogen-fixing nodules, French beans minimize the necessity for nitrogenous fertilizers and leave extra residual nitrogen in the soil for the next crop.

Mulching is a beneficial and inexpensive technique used widely in crop production. It is a process of spreading layers of organic materials like straw, wood chips, hay, dried leaves, grass clippings, crop residues, etc. around the plants or on the soil surface to provide a better growing environment. Mulches, slowly but steadily, protect the soil from erosion, retain moisture, and reduce water usage. Besides, they stabilize extremes of soil pH, suppress weed growth, supply organic matter and humus, provide food and shelter for microorganisms, stimulate healthy root development, maintain soil fertility, and feed plant nutrients to the soil. Timing of mulching is vital because early application in the spring will interrupt production. Heat-demanding crops like French beans should be mulched after the soil has warmed up and this will prevent summer weeds.

Crop rotation is the traditional practice of raising cover crops as well as dissimilar crops in the same farm in a sequence, to benefit long and short-term soil fertility and soil structure. This cultural strategy is powerful in eliminating pests and diseases, minimizing weeds and reducing pesticide and fertilizer use. By way of shifting the approach of production and crops, crop rotation prevents soil deterioration, gives nutrients for successive crops, diminishes pest cycles, provides above-ground habitat for beneďŹ cial organisms, and increases biodiversity and steady production. Succeeding crops for French beans include vegetables like cabbages, broccoli, Brussels sprouts, kale, etc. Root crops such as carrots, beets, radish, parsnips, turnips and rutabaga are favorable preceding crops. Cultivating French beans in a rotation with companion crops like sweet corn, celery and potatoes is recommended.

Cover crops or Green manures are raised especially for taking advantage of their capability in improving yields, enhancing soil fertility, recycling nutrients, adding organic matter to the soil, preventing soil erosion, and suppressing weeds. These plants are economical and essential part of a rotation or an intercropping system. Cover crops modify soil structure, prevent soil deterioration, limit runoff and weathering effects, and develop better drainage by covering the ground. Organic farmers use green manures/cover crop as part of a crop rotation and as living mulch or surface mulch and afterward, they are plowed back into the soil. French beans can be grown as an annual cover crop and incorporated into the soil as a green manure.

Weed and Pest Control is necessary in agriculture production for protecting the crops from unwanted and problematic biological organisms. Plant diseases, pests, and weeds are eliminated or suppressed through cultural, biological, chemical or mechanical control. All these methods are jointly used in Integrated Pest Management to achieve success. Organic farmers prefer biological and cultural practices such as crop rotation or companion planting, intercropping, using certified seeds and right planting time, allelopathy methods, providing beneficial habitats, regular scouting, maintaining the environment clean, limiting pesticides and fertilizers, etc.

Beans are prone to many diseases and pests. Reduce halo blight with lime dusting and keeping the leaves dry. Ladybirds, beneficial insects, and Marigolds will help get rid of blackflies. Traps, row covers, and white geraniums (interplant) prevent Japanese beetle attacks. Aphids, Mexican bean beetles and eggs should be destroyed by handpicking, planting early and using organic

3 sprays such as Pyrethrum or Rotenone. Ample row spacing and water spraying are useful for repelling spider mites. Resistant varieties prompt removal of affected plants, and crop rotation will help avoid common mosaic virus and maggot flies. Raising French beans along with pestrepellant companion crops like potato and turnip is favorable for warding off Bean Leaf Beetle.

Disking is a beneficial cultivation method globally practiced in crop production. Organic growers use this traditional procedure a month in advance of sowing or planting French beans. Disking improves the farm land, promotes ridging and surface mulching effect, and encourages vigorous crop growth. Through disking, farmers are able to control weeds, destroy pest and disease habitat, make a uniform bed for planting, loosen and aerate soil, minimize compaction, and conserve fertilizers. Disking encourages fast decay of crop residues and manures, and allows water and nutrients flow deep into the plant roots. The right timing of disking is critical because it affects the vegetative growth and yield, positively or negatively. Disadvantages of disking include dust, soil degradation, loss of crop residue and soil, and cost of labor. Disking wet soils leads to soil compaction, lower yields, and limited root development.

Residue Management: Crop residue management is an integral part of any conservation program. Residue cover protects the soil against soil erosion and increases infiltration capacity.

Decomposition of crop residue depends on carbon and nitrogen content and the placement of the residue. Incorporated residue decomposes faster than the residue applied on the surface. Surface residue management is the most popular erosion control practice in use today.

The fresh residue mass of French beans ranges from 20,500 to 21,000 lbs/acre (4,510 to 4.620 lbs/acre of dry residue). This residue contains 39.9% carbon and 2.49% nitrogen. French beans return 1,800 to 1,840 lbs of carbon and 112 to 115 lbs of nitrogen per acre from the biomass, excluding the root nodules. This crop has thick vegetation with more than 50% canopy cover after 40 days of emergence. The canopy cover ranges from 70 to 91% after 50 days of germination.

The maximum percent canopy cover recorded is 92 on a heavy soil. Leaf area index goes up to a maximum of 2 after 50 days of emergence and the percent canopy cover goes down after 70 days of planting. The maximum root depth recorded in a heavy soil is 19 inches. The percentage of fresh plant residue cover recorded after final harvest is 31.

________________________________________________________________________ Published by Cooperative Extension, School of Agriculture, Research, Extension, and Applied Sciences, Alcorn State University, Mississippi, in collaboration with the USDA/NRCS. Alcorn State University is deeply grateful to the USDA/NRCS for providing funds for this publication. * Corresponding author.