Elevated demand for food owing to increase in population and changes related to diet habits are putting enormous pressure on agriculture for higher production. In order to fulfill the food requirements of herhuge population, Pakistan is spending billions of dollars to import food commodities, out of which costly edible oil is the solitary largest food item. Pakistan is facing an acute shortage of edible oil. Its demand in Pakistan is increasing with increase in population while production of edible oil is not increasing at the same rate. In 2011 total requirement of edible oil in Pakistan was 2.9 million tons while local production stood at 662 thousand tons which was 23% of total availability of edible oil in the country. Remaining 77 % was compensated through imports. Oilseed rape (Brassica napus L.) has been recognized as one of the most important oil crops. At the present Brassicas is the third most important source of the edible vegetable oil world-wide. Pakistan is the third largest importer of edible oil in the world. During 2011 Pakistan’s edible oil imports were 1.7 million tons having worth of US$.1.65 billion. In order to become self-sufficient in edible oil as well as to save precious foreign reserves spent in importing the edible oil, efforts should be made for boosting up the current production level of oilseed crops. The shortage of edible oil can be overcome through vertical expansion, like use of high yielding varieties, crop rotation to prevent aphid attack, availability of quality seed which should be cheap and having less shattering percentage and best IPM and managerial practices.
There are three main classes of oilseed crops in Pakistan i.e. Conventional (Rapeseed, mustard, groundnut, sesame, linseed and castor bean), non-conventional (sunflower, soybean and safflower) and non-true oilseed crops (cotton, corn). Out of these oilseed crops, canola and sunflower have the real potential to reduce this import bill of edible oil sector. Sunflower has performed very well over the years for bringing down the import bill but canola is facing certain problems in the field. Canola crop is mostly grown in rain-fed and semiarid areas of Pakistan, where availability of water is one of the most essential limiting factors disturbing plant growth and development. Major problems related with canola are shattering, non-availability of good quality seed, production of local hybrids aphid attack and lodging. We may overcome the lodging problem through maintaining row to row and plant to plant distances and also making the plants stronger by plant topping. One of the main reasons of low domestic production is that canola has the same season as of wheat which is our staple food. Currently canola is grown on 142 thousand acres producing 70 thousand tons of seeds and 27 thousand tons of oil.
In Pakistan Rapeseed have numerous uses. The seed is normally used as oil for cooking processes. Canola has the potential to fit well in the present cropping systems because of its premium quality oil. Canola (Canadian Oil low in Acids)varieties are also called double zero, double low varieties. The seeds of canola are used to produce good quality edible oil that is fit for human consumption because it has lower levels of erucic acid than traditional rapeseed oils and produces good quality livestock feed because it has reduced levels of the toxic glucosinolates. Canola meets the standards of these toxic components by having less than 2% of erucic acid in its oil and less than 30 μ mol of glucosinolates in one gram of its dry meal obtained after oil extraction. Erucic acid and glucosinolate are considered toxic for both human and animals’ health and have bitter taste. Like sunflower, corn and, soybean, canola oil have low saturated fats as well as like every vegetable oil, it have no cholesterol. Canola is an outstanding break crop for wheat, and its value is thought to be appropriate in part to the to suppress soil-borne cereal pathogens through biocidal compounds discharged by decayed and rottened roots tissues, that reduce disease infections in following crops sown at that area.
There is need to work on increasing the yield of canola by the application of methods which are expected to be non-petrochemical, naturally eco-friendly, cheaper and easily accessible such as normal plant spacing and suppressing apical dominance to promote secondary branches and ultimately yield. The higher economic benefits from canola crop in terms of grain and edible oil can attract the farmer community towards this crop. Canola is a very flexible and elastic plant that can adjust to a wide choice of plant spacing for its ability to increase branches that result in to more pods formation. It has thus the ability to compensate by using yield components at various plant densities. Plant densities govern yield components and consequently the yield of an individual plant.
Plant spacing is an essential agronomic aspect as it is believed to have special effects on interception of light during which photosynthesis takes place that is the energy production medium. Plant spacing also influences the rhizosphere and photosphere exploitation by the plants particularly when spacing is insufficient and the plants bear clustering together. Optimum plant spacing provides the suitable plant density for best possible yield. Spacing has effects on the growth and yield components of the plant so plant population is very essential for achieving optimum crop growth and yield in irrigated conditions. If plant population is high, then net photosynthesis process of the crop will be affected because of less light penetration in the canopy of crop and increase in the competition for available nutrients which will affect dry matter production and grain yield crop. Generally, there is a practice to maintain plant density and spacing according to the conventional planting methods rather than requirement of variety and hence high crop yield is not possible. Adequate plant population at satisfactory plant space facilitates the proficient use of resources. It is one of the common practices among the farming community that they keep plant population of canola very high.They usually do not go for thinning out for maintenance of row-row or plant-plant spacing and ultimately the plant population. These densely grown crops lead to very thin and weak plants that become prone to lodging at later stages. The most common goal of plant spacing is to produce more yields on a given piece of land by making use of resources that would otherwise not be possible by conventional crop production technology. Improved varieties of canola hybrids are capable of yielding higher when grown under optimum plant spacing and fertility level.