What Is Intercropping and Relay Cropping? Suitable Crops and the Technique of Intercropping Maize with Potatoes

Planting means cultivating plants, including the cultivation of various crops, forest trees, fruit trees, flowers and grasses, medicinal and ornamental plants, and so on, including food crops, cash crops, vegetable crops, green manure crops, fodder crops, forage grasses, etc. So what is intercropping (relay cropping)? Which crops can be intercropped? What are the techniques for intercropping (relay cropping) maize with potatoes?

What is intercropping (relay cropping)?

Growing two or more crops in the same field at the same time, spaced apart in rows at a certain ratio, is called intercropping. The two intercropped species have a long period of joint growth. Intercropping often involves tall crops and short crops grown together.

Which crops can be intercropped?

1. Cotton + maize: Intercropping maize in cotton fields can lure insect eggs and reduce damage to cotton seedlings. Sowing 1 row of maize every 10 m in the cotton field (50-60 hills per mu, 2-3 plants per hill) can effectively improve the ecological structure of the cotton field, luring cotton bollworm and Asian corn borer to lay eggs, thereby reducing the number of eggs laid on cotton seedlings. In cotton fields intercropped with maize, the number of eggs laid on cotton seedlings is reduced by 60%-70% on average.

2. Cotton (or rapeseed) + garlic: Intercropping garlic with cotton or rapeseed can repel pests and reduce insect eggs. The bactericidal substance volatilized by garlic——allicin——has a pungent odor that can make aphids harming cotton or rapeseed “retreat three&rdquo, and the occurrence of the second generation of cotton bollworm on cotton is also significantly reduced, while other pests also “flee at the wind&rdquo. According to surveys, in intercropped fields no chemicals were used to control seedling aphids and cotton seedlings did not curl their leaves, while in monocropped fields under the same conditions seedling aphids were controlled twice and the highest rate of curled-leaf plants still reached 25%-28%; in intercropped fields the second generation of cotton bollworm had only 12 eggs per 100 plants, while in monocropped fields the number of eggs per 100 plants was above 500.

3. Cotton + wheat: Wheat-cotton relay cropping, this planting arrangement is very favorable for controlling aphids at the cotton seedling stage. Because of the barrier effect of wheat, wheat-relay cotton not only directly affects the migration of cotton aphids, but the cotton field temperature is also about 1°C lower than that of a monocropped field, and combined with the effect of natural enemies in the wheat rows, seedling aphids can be controlled without pesticide application.

4. Cotton + mung bean: Cotton-mung bean intercropping. In May and June, cotton plants in monocropped fields are small, which is not conducive to natural enemies hiding and perching; in intercropped fields mung bean grows quickly, and the field microclimate is favorable for natural enemies to survive and reproduce, while bean aphids are good food for natural enemies, so the number of natural enemies increases and cotton pests are reduced, generally allowing 1-2 fewer control rounds.

5. Cotton + sorghum: Intercropping sorghum in cotton fields. Planting a small amount of sorghum beside the cotton furrows can lure natural enemies such as spiders, aphidid wasps, hoverflies, ladybugs, and minute pirate bugs to suppress the occurrence and damage of pests such as cotton aphids and cotton bollworms.

6. Maize + cucumber: Intercropping cucumber with maize can reduce the occurrence of cucumber viral disease. Growing cucumber within maize rows can reduce cucumber mosaic disease by 61.6%. Maize stalks can also be used as cucumber trellis poles, saving money and labor.

7. Maize + sweet potato: The branches and leaves of these two crops grow one vertically and one horizontally, which is conducive to ventilation and light penetration and enhances photosynthesis.

8. Maize + pumpkin (or peanut): Intercropping pumpkin or peanut with maize can effectively reduce Asian corn borer damage. Pumpkin nectar can attract the parasitic natural enemy of the Asian corn borer——the black egg wasp, and through the parasitic action of the black egg wasp, the damage of the Asian corn borer can be effectively reduced. In addition, intercropping peanut with maize can also significantly reduce the damage of the Asian corn borer. Maize has pointed leaves and peanut has round leaves, so planting them together will not block each other's light and improves light energy utilization.

9. Maize + hot (green) pepper: Intercropping maize with hot (green) pepper can reduce hot (green) pepper diseases. Due to the shading effect of maize, pepper sunscald and viral disease are reduced by 72% compared with monocropped fields; planting maize and green pepper in alternate rows can reduce green pepper viral disease by 56.9%.

10. Maize + Chinese cabbage: Intercropping Chinese cabbage with maize can reduce many diseases of Chinese cabbage. In fields where Chinese cabbage is intercropped with maize, because the field air temperature is 0.5°C lower and the ground temperature is 2°C lower than in monocropped fields, Chinese cabbage viral disease is reduced by more than 20%, white spot disease is reduced by 18%, and the occurrence of Chinese cabbage soft rot and downy mildew is also significantly reduced.

Appendix: Technique for intercropping (relay cropping) maize with potatoes

1. Select good varieties. For maize, choose high-yield, disease-resistant, highly adaptable hybrid varieties such as Huidan No. 4, Changcheng 799, Jiyuan No. 1, and Beiyu 16. For potatoes, choose high-yield, disease-resistant, highly adaptable varieties such as Hui-2, Hezuo 88, Zhongdianhong, Shengli No. 2, and Xin 85.

2. Sow at the right time. Maize uses 2 kg of seed per mu and is sown on April 15-20; potatoes use 110 kg of seed per mu and are sown on March 15-25.

3. Planting specifications. Intercrop two ridges of potatoes with two rows of maize, that is, 2:2 intercropping. Maize is ridged at 200 cm, with two rows of maize planted, of which the small row spacing is 40 cm and the plant spacing is 18-20 cm, with 3,300-3,700 plants per mu; potatoes are planted as two ridges within the wide rows of maize, with a row spacing of 80 cm and a plant spacing of 30 cm, with 2,200 hills per mu. That is, in a 2 m wide strip, the distance between the two potato ridges is 80 cm, the distance between the two maize rows is 40 cm, and the distance between potatoes and maize is 40 cm.

4. Apply sufficient base fertilizer. Combine nitrogen, phosphorus, and potassium. At sowing, broadcast base fertilizer along the furrow in the maize row furrows, with 50 kg of calcium superphosphate, 5 kg of urea, and 5 kg of potassium sulfate per mu; broadcast base fertilizer along the furrow in the potato row furrows, with 30 kg of calcium superphosphate and 5 kg of potassium sulfate per mu. Or use 30-40 kg per mu of a 10:5:10 ternary compound fertilizer as base fertilizer.

5. Scientific topdressing. Combine timely topdressing with intertillage and earthing up. For maize, apply seedling fertilizer at the 5-leaf stage, with 10 kg of urea per mu; apply jointing fertilizer at the 7-8 leaf stage, with 15-20 kg of urea per mu; apply ear fertilizer at the 9-10 leaf stage, with 20-25 kg of urea per mu; each fertilization should be combined with intertillage and hoeing or intertillage and earthing up. For potatoes, after full emergence, apply topdressing early in combination with intertillage and hoeing or intertillage and earthing up, with 5-10 kg of urea per mu.

6. Pest and disease control. (1) Underground pests: when maize emerges, spray per mu with 2.5% Kung Fu or 2.5% Decis at a 1:1000 dilution. (2) Asian corn borer or aphids: this can be combined with the control of maize northern and southern leaf blight, spraying per mu with 2.5% Kung Fu or 2.5% Decis at 1:1000 dilution together with 18% Yejing at 1:2000 dilution, 40% Fuji No. 1 at 1:1000 dilution, or 75% tricyclazole at 1:5000 dilution for preventive spraying, once every 7 days, for 2-3 consecutive times; (3) Potato late blight: at the potato rosette stage, spray with 58% metalaxyl-mancozeb wettable powder or 70% mancozeb wettable powder at a 1:500 dilution for control, once every 7 days, for 2-3 consecutive times.