Green High Yield and Efficient Cultivation Technique of Rape for Both Vegetable and Oilseed Utilization

Nian LIU, Tianze TANG*, Yan ZHU, Qixin FAN, Daqing MENG, Yingchun LI, Zhifan LI, Jun CHEN

1. Mianyang Academy of Agricultural Sciences, Mianyang 621023, China; 2. Crop Characteristic Resources Creation and Utilization Key Laboratory of Sichuan Province, Mianyang 621023, China

Abstract This paper introduces a set of green, high-yield and high-efficiency cultivation technique of rape for both vegetable and oilseed utilization, including selection of suitable varieties and sowing methods, seedling raising, timely transplanting, field management, pest and disease control, timely harvest, drying rapeseed into storage and so on. The technique not only improves the yield of rape, but also enriches the citizens’ vegetable basket and farmers’ pocketbook.

Key words Vegetable and oil-seed utilization; Rape; Cultivation technique

1 Introduction

Rape is a main oil crop in China and the largest oil crop in Sichuan Province[1-3]. In recent years, in order to meet people’s increasing needs for a better life, the multi-functional utilization of rape has been constantly explored, mainly including oil, industrial, vegetable, fertilizer, feeding, honey and ornamental functions[4-7]. Rape for both vegetable and oilseed utilization means that the main stem or branch flower stalk is picked for food in the bolting stage, and the rapeseed is harvested for oil extraction in the mature stage[8-9]. Oilseed rape flower stalk is crisp and sweet, rich in VC, calcium, selenium, zinc and other nutritional elements, which has gradually become a delicious food on people’s table and is loved by people since it can improve immunity, prevent osteoporosis and improve constipation[10-11]. Double-low rapeseed oil has the lowest saturated fatty acids content and the highest unsaturated fatty acids content, with reasonable composition of polyunsaturated fatty acids. In addition to oil and protein, it is rich in a variety of functional ingredients, such as sterol, vitamin E, β-carotene, plant polyphenols,etc.These active ingredients play an important role in human health, making it the "healthiest bulk edible oil". Previous studies showed that picking tender flower stalk in the bolting stage not only was beneficial to the construction of high-yield population, but also promoted the increase of rapeseed income. The experimental study of Mianyang Academy of Agricultural Sciences showed that rape for both vegetable and oilseed utilization could promote the secondary branching of rape plants and increase rapeseed yield due to the removal of apical dominance after tender flower stalk picking. Therefore, green high yield and efficient cultivation technique of rape for both vegetable and oilseed utilization is a practical high-yield technology summarized through scientific experiment and practice, which is of great significance to the increase of rape yield and farmers’ income.

2 Selection of suitable varieties

The selection principle of rape varieties for both vegetable and oilseed utilization is mainly as follows: excellent quality, high yield, good resistance and wide adaptability, such as Mianyou 32, Guohaoyou 8, Guohaoyou 5,etc.

3 Selection of sowing methods

To achieve high yield of tender flower stalk, the best sowing method of rape for both vegetable and oilseed utilization is seedling raising and transplanting. Liuetal.[12]studied the effects of different sowing and flower stalk picking methods on the yield and economic benefit of "Guohaoyou 5", a rape variety for both vegetable and oilseed utilization, and found that the best sowing method for Guohaoyou 5, as the rape variety for both vegetable and oilseed utilization, was transplanting. The individual rape in transplanting mode grew vigorously and the rape flower stalk was thicker. Due to the late sowing date, the growth of direct sowing rape was weak and the rape flower stalk was thin.

3.1 Selection and preparation of enough seedbedsAt least 66.7 m2of rape seedbed is needed for each 667 m2of transplanting field.

3.2 Seedling raising

3.2.1Seedling bed preparation. The fields with better fertility and convenient drainage and irrigation are chosen for planting. Clubroot is prevented and underground pests are treated in seedling bed. The seedbed land should be finely prepared and adequate base fertilizer is applied. Before land preparation, fresh lime is evenly broadcasted at the dose of 100 kg/667 m2and mixed into the soil to prevent clubroot. 2 kg of "Phoxim" is mixed with 10 kg of fine soil and broadcasted evenly every 667 m2to prevent and control underground pests. 50 kg of rape special fertilizer was evenly broadcasted per 667 m2seedbed and mixed into the soil as a base fertilizer.

Rape seedbed requires flat surface and fine soil. The ridge-bed is usually opened at the width of 1.5-2.0 m, with the surface width of 1.3-1.8 m, and the ditch width of 0.2 m; the enclosure furrow is 0.3 m deep and the median furrow is 0.2 m deep.

3.2.2Timely early sowing. Rape for both vegetable and oilseed utilization is generally sown on September 10 to 20, better early than late. Seeds are selected before sowing, and sick grains, empty grains and small grains are eliminated. When sowing, every 100 g of seeds can be mixed with 500 g of urea, and then broadcasted evenly for many times. A small amount of straw can be used to cover the seeds, so as to facilitate the neat and consistent emergence of seedlings.

3.2.3Seedbed management. Watering is performed at least once a day before emergence, and bed management should be strengthened after seedling emergence. First, uniform seedling and final singling should be carried out as early as possible. Second, top dressing should be conducted rationally. After each uniform seedling, fecal water and appropriate amount of ammonium phosphate (3-5 kg per 667 m2) can be applied once for top dressing. Third, seedlings are controlled by chemicals. According to the seedling status, 20-30 g of paclobutrazol can be diluted with 30 kg water and evenly sprayed per 667 m2seedling bed, which can control seedling flourishing, promote root development, avoid tall seedlings, cultivate strong seedlings, and enhance the resistance to lodging after transplantation. Forth, the diseases should be prevented and treated in time. The seedbed is inspected at any time according to the needs, and the diseases such as rape cataplexy, downy mildew and damping off should be timely controlled. If there are some insect pests such as flea beetle, they can be controlled by beta-cypermethrin or other similar insecticides in time. Aphids can be timely controlled by aphicides.

4 Timely transplanting

Generally in the middle of October, when the seedlings are about 30 days old with 5-7 leaves, strong seedlings are selected and transplanted with soil. Before field transplanting, artificial or mechanical methods should be adopted to prevent excessive weeds or green rice stubble, and clean up debris such as excessive and long straw on the soil surface; or glyphosate is applied for chemical weeding or greening of rice stubble 7 d prior to transplanting. Then ditches and ridge-beds are opened for transplanting, to facilitate drainage and field management. The suitable transplanting density is 6 000-8 000 plants/667 m2. For late sowing and late planting seedlings, the transplanting density should be appropriately increased, generally 8 000-10 000 plants/667 m2. After field planting, some seedlings are kept under the same water and fertilizer management to fill the gaps with seedlings.

5 Field management

5.1 Check seedlings and fill leakAfter the seedlings turn green and survive, they should be inspected in time. The sparse space should be filled with standby seedlings, to ensure the number of seedlings and improve the yield. Water should be irrigated permeably after replanting.

5.2 Intertillage weedingIntertillage scarification can not only eliminate weeds, but also loose soil, which enhances soil aeration performance and improves soil temperature, conducive to root growth. After transplanting, the first intertillage is carried out, mainly with shallow hoeing, and the intertillage depth is 4-5 cm. The second intertillage is carried out before overwintering; 10-15 kg/667 m2urea and 5-10 kg/667 m2potassium are first broadcasted, which are mixed into the soil during intertillage; meantime, hilling is carried out. In the following spring when the temperature rises to more than 3 ℃, the third intertillage is carried out to improve the ground temperature and promote the growth of rape root system.

5.3 Rational fertilizationAt 10-15 d post field planting, 5-8 kg/667 m2urea is diluted with 1 000 kg water for foliage dressing. Before overwintering, 10-15 kg/667 m2urea and 5-10 kg/667 m2potassium are broadcasted. After picking flower stalk, urea can be topdressed at the dose of 5 kg/667 m2.

5.4 Appropriate irrigationIf winter and spring are dry with little rain, watering should be timely carried out, to promote the normal growth of double low rape. When watering, the ditch will be filled with water to 2/3 of the depth, and waterlogging should be drained as the border surface is moist. Ditches are timely cleaned in spring to ensure no waterlogging in the field and reduce the occurrence of pests and diseases.

6 Timely picking flower stalk

When the flower stalk is 35-40 cm tall, 25-30 cm of flower stalks are picked and about 10 cm flower stalks are remained. The main flower stalks are picked, followed by branch flower stalks. The flower stalk picking should be no later than February 10, otherwise the rapeseed yield will be affected. After flower stalk picking, 10 kg/667 m2urea is applied.

7 Prevention and control of diseases and pests

7.1 DiseasesSclerotiniasclerotiorumis a common disease of rape. Measures should be taken to prevent the disease in time, such as ditching for drainage and reducing soil moisture. The period from plant bolting to early flowering is the best control period forS.sclerotiorum, which can be controlled by 50% procymidone WP 1 000 times dilution, or 40% dimethachlon WP 100-150 g/667 m2or 25% prochloraz 100 g/667 m2diluted with 30 kg of water. The agents are sprayed once every 5-7 d for consecutive 2-3 times. The agents should be sprayed by motor sprayer on lower stem and upper branches and leaves, in order to obtain better control effects.

7.2 PestsCabbage caterpillar and aphid are major pests of rape. Physical control is the major measure, supplemented with biological control. According to the phobotaxis of aphids, the alate aphids could be killed by hanging medium yellow sticky trap in rape field with a hanging density of 30-50 pieces/667 m2. Pesticides with high efficiency and low toxicity should be used for chemical control; 20 g/667 m210% imidacloprid can be diluted with 20 kg water to control aphids, or 5% beta-cypermethrin EC 1 000 times dilution can be sprayed to kill cabbage caterpillar.

8 Timely harvest

Artificial or mechanical harvesting is mainly adopted for rape. Artificial harvest is generally employed when more than two thirds of the siliques are yellow brown in the rape field and silique grains at the base of main axis have the inherent color of seed; the rape plants are cut down and dried in the field for 5-7 d before threshing. Mechanical harvesting is divided into combined harvesting and subsection harvesting. Combined harvesting is performed after all siliques are completely withered and yellow. Subsection harvesting is generally adopted when more than two thirds of the siliques are yellow brown in the rape field and silique grains at the base of main axis have the inherent color of seed; the rape plants are cut down and dried in the field for 5-7 d before threshing by a harvester.

9 Drying rapeseed into storage

At the end of harvest, methods such as drying should be adopted immediately to reduce water content, remove impurities, prolong seed storage time, and prevent mildew caused by high temperature and humidity that will affect oil extraction rate. When the moisture content of the grain drops to below 9%, grains are winnowed thoroughly, bagged and put in storage.