Rape is a cruciferous plant with pivot and profound root. When its main root encounters obstacles to deepen, it is capable of developing secondary roots.
1. Taxonomy and Origin
The origin of this crop seems to be in Asia Minor. Subsequently it was cultivated throughout the Mediterranean, in such a way that Greeks and Romans cultivated this plant for food and for medicinal purposes.
2. ECONOMIC IMPORTANCE AND GEOGRAPHICAL DISTRIBUTION
Rape is a traditional oilseed crop in many European countries like France, Germany, England, Poland, etc. Globally, the largest producers are Canada (14.164.500 tons in 2011), China (13.426.012 tons) and India (8.179 million tons).
The cultivation of rape plant takes a considerable importance due to the increase in demand that is being carried out by the biodiesel industry as well as its price. Rapeseed oil is a commodity of interest for this industry, which has resulted in increased planting areas. Moreover, rape is used to obtain oil for human consumption, flour and feed.
Rape has been regarded for years as a marginal crop, with average yields around 1500kg/ha. However, in recent crop seasons, there have been significant increases in yields, mainly due to the planting of new varieties and hybrids, as well as the use of more specific growing techniques.
- An annual herbaceous plant which can be extracted oil from its seeds.
- Rape is a cruciferous plant with pivot and deep root. When the main root encounters obstacles to deepen, it can easily develop secondary roots.
- The stem is erect with a size of approximately 1.5m.
- The leaves are petiolate. The lower leaves are characterized by serrated margins while upper leaves are heart-shaped.
- The flowers are small, yellow and grouped in terminal clusters.
- The fruits are pods and the number of seeds per pod is 20-25 depending on the variety. Ripe pods are dehiscent and the sutures are opened with blows or when they are dried in the sun. The grains fall to the ground.
- The seeds are spherical, 2 to 2.5 mm in diameter and, once they mature, their colour is reddish brown or black. The composition of rapeseed is:
Rapeseed consists of a major proportion of oil (39%).
4. EDAPHOCLIMATIC REQUIEREMENTS
- Temperature: it does not tolerate temperatures below -2ºC from seedling to rosette stage. In this state, it can tolerate up to -15ºC. The cold may even enhance root development.
It should be known that low temperatures together with short-day periods delay ripening and during flowering, high temperatures are not suitable because they shorten the cycle and the grains would not be of high quality.
- Water needs: Rape can develop from 400mm rainfall if they are well distributed. It is a crop that can resist winter drought and suffers with waterlogging.
- Irrigation: 2-3 irrigations are recommended with total water applied between 120-200mm for maximum grain yield. Approximately 30% of the water should be applied from nascence period until the beginning of flowering and the remaining 70% from the start of flowering to maturity.
- Soil: The rape plant prefers deep soils with silty-clay textures with good aeration and drainage. The pH range of 5.5-7 is desirable but can be grown in any type of soil; it can even support a certain degree of soil acidity.
5. PROPAGATION AND VEGETAL MATERIAL
The success of the crop will depend largely during planting period. It should be kept in mind that planting should be done as early as possible so that the rape plant reaches the rosette stage (6-8 true leaves) before the arrival of winter frost. Therefore, it is recommended that the planting time in Spain is in September. However, if the chosen planting time is in the spring, it should be from late January to mid-February.
There are two types of rape varieties: winter type and spring type, differing in the necessary hours-cold for flowering. The results confirm that the varieties with higher yields have an average flowering cycle between 115-120 days. Delight, Williams, Aurore and Sary varieties are highlighted with production yields between 3500-4000kg/ha.
In rape growing, nitrogen is a very important nutrient and it is even considered to be the basis of its production yield. This nutrient is responsible for increasing the number of pods and their corresponding grains. With regards to phosphorus and potassium consumptions, it should be borne in mind that the input of these elements increases during flowering and from the nascence period to flowering respectively. Sulfur input is also important as it requires a sustained uptake throughout the whole cycle and this increase during the grain formation process.
It is important to decide the date of harvest accurately as this will affect grain yield and oil quality. The parameters that are commonly used to determine this date are grain moisture (should be around 9%) and /or the whitish color of the seeds.
It is recommended to do the harvest during the early hours of the morning or in afternoon, avoiding the hottest hours which is when the shelling is greater.
8. PESTS AND ILLNESSES
Rape stem weevil (Ceuthorrhynchus napi): The larvae of this insect deforms the stem of rape, which is curved and often splits at some length. Severely attacked plant flowers later and its seeds do not ripe well. Chemical treatment is not often used to control this pest.
Terminal bud weevil (Ceuthorrhynchus picitarsis): Adults are harmless, but the larvae destroy the terminal bud and force the plant to produce side shoots.
Silique weevil (Ceuthorrhynchus assimilis): Adults bite young siliques and larvae gnaw the seeds, which can cause a significant decrease in the harvest. Moreover, these injuries can also be gateway of illnesses during wet seasons.
Cecydomia (Dasyneura brassiceae): The larvae of this insect destroy completely the siliceous.
Meligethes sp: Adults are responsible to crack the buttons of the rape; the younger the buttons, the more severe the attacks. When flowering begins, the damage decreases. The larvae scarcely cause damage.
Rape flea beetle (Psyllodes chrysocephala): Adults appear in autumn rapes fields, usually shortly after nascence, nibbling the smaller leaves and can destroy many plants.
Cabbage flea beetle (Phylotreta sp.): Adult insects hibernate overwinter in the soil from September and appear in April.
Black spots (Alternaria sp.): This disease causes some elongated spots on the stem and petioles. It requires an environment with high humidity and temperatures above 18°C. The rain spreads its spores within the same plant or other nearby plants, and the wind is responsible for transporting over long distances. Control method: use resistant varieties and destroy the remains of previous crops.
Phoma lingam: This disease occurs when there is dew or rain and when temperatures are close to 15-18°C. This fungus can live on the ground for 3 years, so the crop should not be repeated in that span of time.
Gray rot (Botrytis cinerea): It is caused by a fungus that forms sclerotia in plant residues on the ground. Damaged parts are coated with gray or brownish rust. Preventive measures: do not plant in too wet grounds and destroy crop residues.
Clubroot (Plasmodiophora brassicae): The first symptom of this disease is temporary wilting of leaves, later; the plant development is delayed relative to the other and may end up dying. Generally, this illness is not present in soils with pH equal to or greater than 7.
Sclerotinia sclerotiorum: The attacked plant is covered with mould or whitish fuzz.
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