Do Rotations Matter within Disease Management Programs?

As agricultural land becomes more scarce, existing farms become more specialized, and land closest to roadside markets increases in value, in part due to the advertisement-value of growing some crops where they can be seen and/or harvested by customers, an increasing number of farmers are considering shorter rotations for some of their plantings. Indeed, it can be very tempting to shorten rotations. What would happen if one were to ignore rotations, that is, if one were to plant the same crop in the same field year after year? This was done in Penn State research fields for both tomatoes and for muskmelons. The results are summarized below in Table 1 (tomato early blight) and Table 2 (muskmelon/cantaloupe Alternaria blight).

Table 1. Defoliation associated with Alternaria early blight on tomatoes after growing tomatoes in the same field for 1, 2, 3, and 4 successive years).

Successive Years	% Defoliation when 5% Fruit were Ripe
Year 1	3
Year 2	30
Year 3	74
Year 4	70

Table 2. Date when Alternaria blight first appeared on muskmelons (cantaloupes) for successive years after muskmelons were grown repeatedly in the same field (from 1977 through 1981).

Successive Years	Years Grown	First Date when Alternaria Blight was first observed	# Days before August 8	# Days after June 1
Year 1	0	August 8	0	69
Year 2	1	August 3	5	64
Year 3	2	July 29	10	59
Year 4	3	July 25	14	55
Year 5	4	July 18	21	48

The results provide a clear indication of the value of rotations relative to diseases caused by pathogens that can survive either in soil or in association with refuse from diseased plants. Many vegetable diseases are in this category.
Traditional wisdom and common-sense, combined with results such as those presented in tables above, tell us that rotations are important. Interpretation of results from various field, greenhouse and lab studies, and observations by many plant pathologists, suggest a minimum number of years that a grower should avoid growing crops affected by specific diseases (See Table 3). All vegetable growers should consider this information seriously as they plan crop rotations within their disease management programs.
Table 3. Minimum years to avoid crops susceptible to specific diseases.

Vegetable	Disease	Period without a susceptible crop
Asparagus	Fusarium wilt & root rot	Indefinite; do not plant without fumigation
Beans	Root rots	3 years; use grain crops, including sweet corn in rotation
	White mold, Sclerotinia	3 years; avoid tomato, potato, lettuce,cabbage, celery, carrot
	Anthracnose	2 years
	Bacterial blight	2 years
Beets	Cercospora leaf spot	3 years
	Root rots	3 years; use grain crops, including sweet corn in rotation
Cabbage-related plants	Clubroot	7 years; avoid turnip, radish; adjust pH to 6.8 or above
	Fusarium yellows	Many years
	Blackleg	3-4 years; avoid turnip
	Black rot	2-3 years; avoid turnip
	White mold	3 years; use grains crops, including sweet corn in rotation
Carrots	Leaf blights (fungal & bacterial)	2-3 years
Celery	Leaf blights	2 years
Corn, sweet	Smut	2-3 years
	Yellow leaf blight	3 years
	Northern leaf blight	2 years
Cucumber	Scab, GSB, & leaf spots	2 years
Eggplant	Verticillium wilt	4-5 years; avoid tomato, potato, pepper, strawberry, brambles
	Fruit rots	3 years
Lettuce	Bottom rot (Rhizoctonia)	3 years
	Drop, Sclerotinia	3 years; avoid tomato, potato, beans, cabbage, celery, carrot
Muskmelon=cantaloupe &Watermelon	Leaf spots, GSB, & scab	2+ years; avoid other cucurbits
	Fusarium wilt	4+ years; watermelon Fus. wilt is different
	Gummy stem blight (GSB)	2 years; avoid muskmelon, pumpkin, squash
	Fusarium wilt	4+ years; muskmelon Fus. wilt is different
Onion	Leaf blights	1-2 years
Parsley	Damping-off	3 years
Parsnip	Leaf spot & root canker	1 to 2 years
Peas	Root rots	3 to 4 years
	Fusarium wilt	4 to 5 years
Peppers	Bacterial spot	2 years
	Phytophthora blight	3 years; avoid tomato, eggplant, cucurbits
Potato	Verticillium wilt	3-4 years without tomato, eggplant, pepper
	Sclerotinia stalk rot	4 years; avoid tomato, lettuce, beans, cabbage, celery, carrot
	Rhizoctonia canker	2-3 years; best with 2 yr. grass or 1 yr cereal
	Silver Scurf	2 years; primarily from seed tubers
	Early blight	2 years; avoid tomato
	Pythium leak; pink rot	4 years
	Common scab	2-3 years; no root crops; adjust pH to 5.2 or below
Pumpkin, & Winter squash	Angular leaf spot	1-2 years
	Black rot (GSB)	2+ years; avoid muskmelon, watermelon, and other cucurbits
	Fusarium crown and fruit rot	3 years; avoid other cucurbits
	Phytophthora blight	3 years; avoid tomato, pepper, eggplant, and other cucurbits
	Scab	2 years
Radish	Clubroot	7 years; avoid turnip, cabbage-related plants; adjust pH to 6.8
Turnip	Clubroot	7 years; avoid radish, cabbage-related plants; adjust pH to 6.8
Spinach	Downy mildew & white rust	2 years
Sweet potato	Black rot & scurf	3 years
	Pox (soil rot)	Few years; reduce soil pH below 5.2
Tomato	Bacterial canker	3+ years
	Bacterial spot	2 years; avoid pepper
	Bacterial speck	1 year
	Early blight	2 years; avoid potato
	Anthracnose	2-3 years; avoid potato
	Septoria leaf spot	1-2 years
	Fusarium wilt	3 years
	Verticillium wilt	Several years; longest possible; avoid potato and eggplant

Article adopted from Vegetable MD Online For original article

Mother Nature deplores a vacuum

Crop rotations help prevent the buildup of weeds adapted to a particular cropping system. Certain weeds are more common in some crops than others. Pigweed, lamb’ squarter, common ragweed, velvetleaf, cocklebur, foxtail species, and crabgrass are found in summer-cultivated crops such ascorn. Mustards, wild oat, wild garlic, chickweed, and henbit are associated with fall-sown small grains. Pastures often contain perennial weeds such as ironweed and thistles. Changing crops changes the cultural conditions (planting date, crop competition, fertility, etc.) that a weed must tolerate. Rotating crops also often means that a different set of management tools (especially herbicides) will be used. The overall success of crop rotation in managing weeds depends on the ability to control the weeds in each crop grown in the rotation.

Rotation will prevent a weed species from becoming dominant in a field but will also maintain a diversity of weed species in the same area.  Crop rotation historically was very important for managing weed problems. Today, rotation is used more for managing diseases and insects than weeds. Rotation requires the farmer to have additional knowledge and to use additional equipment to manage the various rotational crops. Even with an abundant supply of fertilizers and diverse herbicides that make it possible to minimize the need of crop rotation for weed control, there are still sound reasons to rotate crops for environmental and pest management reasons. For example, corn rotated with soybeans consistently yields more than corn grown continuously in the same field. Rotation of vegetable crops is important to avoid buildup of soil diseases that reduce crop yields. However, rotation is not an option with long-term perennials such as orchards, forest trees, nurseries, and perennial forages. Some of the benefits of rotation can be retained in monoculture cropping systems by the selection of a variety of herbicides, especially those differing in mode of action, and the use of various cultural practices, especially cultivation.

Herbicide diversity and cultivation help prevent the development of resistant weed populations that are adapted to an unchanging herbicide program and crop.  Problems tend to arise when farmers do not rotate their crops and pest management strategies in an integrated manner. For example, in the past the corn–soybean rotation avoided the buildup of corn rootworm in the corn cycle, as rotation for 1 year to soybean broke the insect life cycle. However, the insect has adapted to these cropping strategies to be able to survive on soybean and has once again become a major corn problem. Similar examples are available in weed control. With the availability of a variety of glyphosate-resistant crops, there will be a tendency to continually use glyphosate for weed control even as we rotate crops. This is poor management, and it will become necessary to rotate herbicide-resistant crops with nonresistant crops to avoid a buildup of weeds not well controlled by glyphosate. The same holds true for herbicides that inhibit branch chain amino acids and can be used in many of our major acreage crops. There is a law of nature that holds true for agriculture that one should always remember: “Mother Nature deplores a vacuum.” Repeated use of any successful pest management practice without appropriate integration with a variety of other tactics and rotation over time will result in that tactic’s selecting for its own extinction. There are many good examples of this phenomenon in weed science, and they are called herbicide-resistant weeds

All About Coriander

Dr. K. T. Chandy, Agricultural & Environmental Education

I. Introduction

Coriander (Coriandrum sativum) is a minor aromatic annual condiment and spice crop. It is native to Mediterranean region and commercially grown in India, Morocco, ex-USSR, USA, Hungary, Poland, Rumania, Mexico, etc. India is the largest producer of coriander in the world. It is being cultivated in an area of about 3 lakh hectare. The important states in which it is grown in India are Rajasthan, Andhra Pradesh, Tamil Nadu, Madhya Pradesh, Maharashtra, Gujarat and Karnataka. Its leaves and fruits are used in flavouring food and to suppress offensive odours in pharmaceutical preparations. Its fruits are exported to an extent of Rs 35 million. It is a highly remunerative crop. 

II. Climate

Coriander is a tropical crop. It can be successfully grown on a wide range of climatic conditions but it thrives well in sunny locations. A temperature range between 15°C to 25°C is suitable for its seed germination and between 10°C to 25°C is favourable for its vegetative growth. A dry and cold weather favours higher seed production. Cloudy conditions at flowering and fruiting stage increases pest and disease incidence.

III. Soil

Coriander can be grown on all types of soils. Under irrigation when sufficient organic matter is available in the soil and under rainfed conditions, black cotton soils, having high water holding capacity are the best soils suitable for its growth. It can grow on a wide range of soils from sandy loam to black clayey soils, also in slightly alkaline (PH 8.0) and non-saline soils. 

IV. Varieties

Important varieties of coriander are described below.

1. CO-3

This variety was developed at Coimbatore as pure line selection. It has high yield potential, dual purpose and is less susceptible to wilt and grain mould. The grain is medium in size, brownish yellow in colour having 0.4% oil. It matures in 90 days, yielding 640 kg\hectare.

2. CS-287

This variety was developed at Coimbatore by recurrent selection from CS-6 variety of Andhra Pradesh. It is a short duration variety having small bold grains. It is tolerant to wilt and grain mould. Suitable for rainfed tracts, it matures in 78 days yielding 510 kg\hectare.

3. Lam Sel. CS-2

This variety was developed at Guntur by mass selection. It is a medium tall, bushy type variety with more number of branches. It is a grain purpose variety, tolerant to pests and diseases with good quality grain having 0.4% oil. It matures in 110 days yielding 1300 kg\ hectare.

4. UD-20

This variety was developed at Jobner. It is a medium tall plant with bold grains. It matures in 100-110 days yielding 1175 kg\ hectare.

5. Pusa Selection-360

It is recommended for Rajasthan and Maharashtra states. Plant height is about 60 cm. It produces large number of umbellets per plant and yields about 40 g of grains\plant. It yields about 1250 kg\hectare.

6. UD-21

This variety was developed at Jobner (RAU). Medium tall variety which matures in 90 days, produces about 21 umbels with 75 umbel lets per plant. It yields about 700 kg\hectare.

7. Cimpo 8-33

This is a new promising variety introduced from Bulgaria. It is late maturing with taller growth habit. It has fine seeds, rich in essential oil-content (1.3 per cent). It matures in 180-190 days yielding 18-20 quintals of grains per hectare.

8. CO-2

CQ-2 is a popular dual purpose and a widely cultivated variety. It is suitable for culinary purpose as well as for production of grains. It gives a leaf yield of 100 quintal\ hectare in 40 days after sowing and 6-8 quintal of grains per hectare in 100

days. The essential oil content is. moderate i.e. 0.3 to 0;48 per cent.

9. Morrocan

Medium sized seeds with high oil content. Yields about 10-12 quintals grains per hectare, maturing in 150 days.

10. Gwalior No-5365

It is a medium-tall short duration variety, maturing in 85 days with bushy type branches. It is free from powdery mildew disease due to its early maturing habit. Hence it is recommended for areas where dew fall is high.

11. Russian varieties

Strains like A-26, A-247, A- 704 and Roose have been developed in Russia. These are high yielding varieties, with high essential oil contents.

V. Field Preparation

Under rainfed conditions the land is ploughed 3-4 times with the onset of monsoon. Ploughing and harrowing continues whenever it is possible during rainy season to remove the weeds and other plant residues. Fields are kept open to absorb maximum lain water. After rainy season, ploughing is followed by planking to conserve the soil-moisture required for sowing.

Under irrigated conditions, the fields are irrigated after rainy season is over and previous kharif crop has been harvested. It is ploughed 2-3 times, harrowed to collect weeds and stubbles and finally planked to conserve soil moisture for sowing. After sowing, field beds and water channels are made. 

VI. Manures and Fertilizers

Application of 10-15 tonnes of well rotten farmyard manure at the time of last ploughing one month before sowing is beneficial. In addition to it, 20 kg nitrogen, 30 kg phosphorus and 20 kg potash per hectare in the form of fertilizers is recommended for a good crop under rainfed conditions. For irrigated crop, the nitrogen should be increased to 60 kg per hectare and it should be split into two equal doses. First one is applied as basal dose and the second one about 45 days after sowing.

VII. Irrigation

Coriander sown under rainfed conditions or on black cotton soils require mostly no irrigations. But otherwise, number of irrigations for light soil vary with seasonal rains. Normally 3- 4 irrigations are required during whole crop period. First one at two-leaf stage i.e. 30 days after sowing, the second at branching or flowering stage i.e. 75 days after sowing and the third at seed filling stage i.e 110 days after sowing. It is beneficial to maintain sufficient available soil moisture at the time of flower irrigation stage.

VIII. Seed and Sowing.. .

Important aspect of sowing coriander are described here.

1. Selection of seed

About 12-15 kg of seed is required for sowing in one hectare. The seeds are split into halves by rubbing before sowing. The split seeds germinate a little earlier than other seeds. Soaking the seeds in water for 12-14 hours and drying them in shade for 12 hours also helps to obtain quicker germination.

2. Seed treatment

Before sowing, seeds are treated with suitable fungicides like Thiram at the rate of 2.5 g per kilogram seed as a measure against stem gall disease.

3. Spacing and sowing

The seeds are sown in lines with a spacing of 25 cm between rows and 15 cm between plants. Three to four seeds are sown per hill, later on thinned to two plants per hill. Some times seeds are sown by broadcasting and after that they are mixed with the soil using rake. Seed gem1inates in about 10-12 days.

4. Time of sowing

The best period for its cultivation is from October to February. An irrigated crop is raised in June-July and September-October. 

IX. Weed Control

Weed control, with the help of hand hoe or khurpi is advantageous, as it (1) removes the weeds thoroughly and gently, (2) produces mulch to conserve soil moisture as is the requirement of rainfed condition, (3) improves soil aeration, and finally (4) thinning and spacing of plants is also done while hoeing. Under irrigated condition, additional one or two hoeings sometimes are given to reduce the weed menace.

X. Insect Pests

A number of insect pests are found to attack coriander. Some important pests are discussed here.

1. Aphids

Aphid (Hyadaphis coriandra) is a prominent pest damaging the crop by sucking the cell sap from inflorescence (umbel) in February and March, To control aphids (1) grow relatively resistant varieties like UD-20, Pusa Selection 360 etc., (2) spray the crop before flowering with Endosulfan or Phosphamidon or Monocrotophos @ 0.03 per cent, and (4) predators like Coccinellai repunctata, Menochilus sexmaculatus and Adonia variegata control the aphids by feeding on them.

2. Brown wheat mite

The brown mite (Petrobia latens) appears; during the first week of March. It can be controlled by spraying before flowering with Endosulfan or Phosphamidon or Monocrotophos 0.03 per cent.

Many other insects, causing minor damage to coriander crop are Lucerne caterpillar (Spodoptera exigua), pentatomid bug (Agnoscalis nubila), surface grass hopper (Chrotogonus trachypterus), white fly (Bemisia tabica), green peach aphid (Myzus persicae) and thrips (Thrips tobaci). These can be effectively controlled by spraying Monocrotophos or Nuvacron I0.05 per cent at 10 -15 days interval, or Kelthane (Dicofol) at the rate of 3 ml per litre of water or spraying 0.05 per cent Dimecron or Rogor. 

XI. Diseases

Among diseases, powdery mildew, wilt and stem gall are important. To control these diseases (i) spray wettable sulphur 0.25 per cent at flowering stage, and subsequently at 15-20 days interval or dust the crop with 20-25 kg sulphur per hectare. This will control the powdery mildew disease effectively. There are no direct control measures available for wilt disease. However, selection of disease free seeds, seed treatment with fungicides, use of crop rotation, etc. are some of the preventive measures suggested to control the wilt disease. Stem-gall disease is also difficult to control. Some preventive measures suggested to control this disease are (i) sowing seed of resistant varieties like UD-41 or Karan, (2) treating seed with Agrosan GN @ 2.5 g/ kg seed before sowing, and (3) use of 3-4 years crop rotation.

XII. Harvesting

Harvesting of coriander for seed is done when 75 to 80 per cent of seed capsules in the umbel turn yellow. Delay in harvesting should be avoided, since it will cause shattering of seeds during harvesting. Plants may be harvested during early hours of the day to reduce loss due to shattering and harvested plants may be cured in shade to get good colour to the final fruit produce and to avoid loss of flavour.

XIII. Threshing

The seeds are extracted by beating with a wooden stick and are winnowed and cleaned. To minimize moisture content, they are dried in open bright sunlight and stored in polythene bags.

XIX. Mixed Cropping

The plants of coriander do not create any problem in space and competition for sunlight, hence can very well be grown as mixed crop, or sow a few lines in crops like wheat, linseed, rapeseed and mustard, sugarcane, potatoes, winter vegetables etc. 

XV. Crop Rotation

Coriander crop can be sown after the harvest of kharif crops. Therefore, it can be grown in various combinations.

1. Paddy-coriander-wheat : 2. Maize-coriander-sorghum, 3. Cotton-coriander-maize , 4. Maize-coriander-green manuring -potato –sugarcane (ratoon), 5. Bajra-coriander-wheat-maize

Since it is a short duration crop, it makes adoption of cropping with most of the crops.

1. Maize-coriander-moong, 2. Soyabean-coriander-iobia, 3. Maize-coriander-cbeena.

XVI. Unfavourable Climate

Heavy rains and wind climates are not suitable for its growth. Fluctuations in atmospheric temperature immediately after germination cause wilting and poor crop stand. Heavy rains and frost during plant growth period cause rotting. High humidity at the flowering and fruiting increases pest and disease incidence and causes poor seed set.

XVII. Medicinal Value

The leaves and tender stems of coriander are used for the treatment of ailments like dyspepsia, flatulence and piles. The dried seeds are said to have diuretic, aphrodisiac properties. Coriander is also used as an ingredient in many Ayurvedic medicines prescribed for curing ailments concerning indigestion, diarrhea, dysentery, cold and urinary troubles. It has pleasant aroma and, therefore, used to arrest offensive odours in pharmaceutical preparations. Fruits are also used in medicines as stimulant, carminaitve, stomachic and heart tonic. 

XVIII. User's Products

Leaves and fruits of coriander plant are fragrant. The pleasant aroma is due to an essential element called d-linalol or cordianderol. The oil content ranges from 0.1 to 1.3 per cent in dry seeds. The dried ground fruits are used as condiment and is a major constituent of curry powder for flavouring curries and soups. The whole or ground fruits are also used to flavour food like sauces, pickles and confectionery. The essential oil obtained by distilling the fruits is used in perfumes, soups, candy, cocoa, chocolate, tobacco, meat, products, alcoholic beverages and to mask offensive odours in pharmaceutical preparations. The leaves and tender sterns are used raw in salad and are rich source of vitamin C and A. Besides, their culinary uses they are also used for the treatment of ailments like dyspepsia, flatulence and dried seeds are used in various medicines. The oil in western countries is used for flovouring liquors like gin, beverages and variety of foodstuffs. It is also used for the synthesis of citrol from linalol which the oil contains and subsequent synthesis of vitamin' A' from citrol. Besides essential oil, the seeds contain 21 % of fatty oils which are used in the manufacture of soaps. Coriander is exported to countries like Malaysia, Singapore, Australia and Central European countries to earn foreign exchange worth Rs.35 million every year.

XIX. Economics of Cultivation

Most of the coriander growers do not maintain farm record or accounts properly, so it is very difficult to make out whether the enterprise is at loss or profit. This is due to the ignorance of proper method of cost benefit calculations. Given below is a format for determining the cost benefit of coriander cultivation. From this format a grower can choose, whatever is applicable to him. 

A. Fixed cost "

1. Cost of the land Rs
2. Cost of farm building storage structure, etc. Rs
3. Cost of fencing Rs
4. Cost of the clearing, leveling and bunding Rs.
5. Cost of machines, implements instruments and other accessories Rs.
6. Cost of other permanent or semi-permanent structures Rs

 

B. Recurring cost

1.    Cost of seeds Rs

2.    Cost of manures and fertilizers Rs

3.    Cost of insecticides, fungicides and weedicides Rs

4.    Cost of farm power Rs

5.    Transportation Rs

6.    Cost of farm labour (paid and unpaid) Rs

a.    Cost of land preparation Rs

b.    Cost of Irrigation Rs

c.    Cost of Weeding Rs

d.    Cost of application of fertilizers and manures Rs

e.    Cost of application of insecticides and fungicides Rs

f.     Cost of other intercultural operations Rs

g.    Harvesting and threshing Rs

h.    Processing Rs

i.      Storing Rs

j.      Any other Rs

7.    Interest on fixed cost (@ 10%) Rs

8.    Rent or revenue paid for land Rs

9.    Depreciation

a.    Farm structure Rs

b.    Farm implements Rs

10.  Repair and maintenance Rs

11.  Crop Insurance Rs

12.  Total recurring cost Rs

 

Income

1.    Grain yield Rs

2.    Green crop sale Rs

3.    Any other Rs

Gross income Rs

Net profit = Gross income -Total recurring cost

Purchase value -Junk value

Depreciation = ----------------------------------------

Life span

Remark: Junk value is calculated only on those articles that are saleable after their life span. Life span of building and machinery is 15 years and 10 years, respectively.