Choking

• Most types of weeds grow much quicker and require much less care than any type of intentional crop. As a result, their growth in a field overtakes the seeded crop in years when they have proliferated extensively. They seize the available soil space and nutrients and make it much more difficult for the crop to establish at any sort of reasonable growth rate. Many of the seeded plants will not even survive if the weeds are too bad. This is sometimes called "choking out" a crop.
  
  

Final Crop

• If you don't control the weeds properly in a crop, harvest time can be a truly disastrous mess. This is especially true of oilseed, cereal and pulse crops rather than things like vegetables. When a combine harvests these types of crops if weed populations are high, it also takes in a high percentage of weed seeds. The result is a product contaminated with weed seeds.
  
  

Revenue

• Weeds cause a loss of revenue to the farmer because the cost of controlling them is considerable. Pre-working the soil costs fuel and causes wear and tear on the equipment. Spraying the fields for weeds is one of the major costs farmers have to contend with every year. The cost of herbicide combined with the cost of fuel for the sprayer or the cost of hiring a spray pilot account for a major annual expenditure.
  
  

Corrupted Seed Stock

• Unless they are planting seed that has a contract forbidding the carry over of seed stock, most farmers keep seed from their crop one year to replant the next. If a crop is full of weeds, that seed is unsuitable for planting. The result will either be a terribly weed- infested field in the following year, or an additional cost for the farmer when he has the seed cleaned well to remove all traces of any harvested weeds.