FARMING WITHOUT CHEMICALS

  • Written by Andrew Davis
  • Posted on May 26, 2022
  • Articles

If we are to feed the world’s population, we must produce as much food over the next fifty years as we have done throughout the history of humanity, all without wrecking the planet.  With priorities of climate change mitigation and reversing the decline of wildlife as well as providing food, can that be achieved by farming without the use of chemicals, synthetic fertilisers and pesticides?  That was the question for debate at the recent meeting of the Countryside Forum.

 

The answer is no or, at least, not yet.  Scientists are making huge strides in research but it may be twenty years before we can produce enough food without extensive use of nitrate fertiliser and pesticides.  Global yields would fall by 40% if we were to cut out pesticide use now, 45% from weeds, 30% from insects, 20% from disease and 5% from other causes.  But, by exploiting emerging technologies and integrated pest management, we can reduce their use and impact on the environment.

 

Starting with crop nutrition, I was shocked to learn that nutrient use efficiency is only 66% and that has increased from 30% in 1961.  That means that a third of the fertiliser applied to crops is wasted, volatilised into the air as greenhouse gases or washed into watercourses leading to diffuse pollution.  Of course, the Holy Grail of crop production would be for cereals and other crops to have the nodules on their roots containing bacteria that fix atmospheric nitrogen as legumes and pulses do.  Scientists at Rothamsted Research and elsewhere having been working on this for some years and are convinced that it is possible but is still ten to twenty years in the future.

In the meantime, we must make sure that we minimise loss by integrated crop management and precision agriculture, only applying the right amount of fertiliser at the time the crop can use it.  Gene editing can improve the nutrient use efficiency of the crop and there are soil borne bacteria that can fix nitrogen or make phosphate more available to the plant.  The use of fertiliser supercharges the soil biome, encouraging the microorganisms to break down organic matter, which has led to the degradation of soils.  Increasing organic matter is a critical priority and one way to do that is by rotation of crops.  Growing legumes and pulses in the rotation improves soil fertility and organic matter content.

Plant protection products are under huge pressure with many being banned or withdrawn due to the EU’s adherence to the precautionary principle based on hazard rather than risk, neonicotinoid insecticides for example.  This has led to an increase in time and cost to develop a new pesticide, now put at £300 million and eleven years.  Manufacturers are understandably reluctant to invest that time and money if the chemical is likely to be banned after a few seasons.

Fortunately, there are alternatives that are increasingly being developed.  For weed control, there are mechanical means, for example, light robotic machines hoeing between rows or zapping weeds with lasers.  The Small Robot Company has launched Tom, Dick and Harry; Tom is a surveillance tool that gathers information about the crop, its nutritional needs and weed, pest and disease pressures, Dick has a laser to zap the weeds whilst Harry can sow seeds.

Biological products are bioprotectants or biostimulants.  The former are natural products that can be applied to crops to control pests, weeds and diseases.  Elicitors stimulate plant defence mechanisms, for example Ressivi reduces viral multiplication in crops.  Pheromones are the natural chemicals released by organisms to attract or repel their fellows.  Within the next five to ten years it should be possible to synthesise insect pheromones that warn a specific insect to stay away from the crop.  Biostimulants include the bacteria in the soil that can make phosphate more available to the plant or others that can fix nitrogen and act as growth promoters.  Phosphites reduce stress in the plant which leads to more nitrate uptake and less wastage.

Companion cropping has been developed more in areas such as Africa than in the UK.  For example, when growing a crop that is susceptible to a particular pest, growing a strip around it of another species that is not attractive to the pest can offer a level of control.  Growing a legume as a companion crop can provide nitrate and improve soil fertility.  A strip of wild flowers or a beetle bank through the middle of an arable crop can act as host to predatory insects to control others such as aphids.

Perhaps the most common use of companion cropping in this country is now oilseed rape production.  Since the ban on neonicotinoid insecticides, farmers have struggled to combat the damage caused by cabbage stem flea beetle.  By adjusting the sowing rate of new hybrid varieties and by growing in a mixture with companion species, some progress has been made.  Common mixtures include buckwheat to provide a protective canopy, fenugreek with its deterrent odour and berseem clover to add nutrients.

The starting point for all these innovations is a sound soil structure and fertility.  Farmers need to grow a far broader rotation of crops to include legumes, pulses and green manures.  Gene editing, likely to be approved in this country in the near future, has huge potential and will produce new varieties with improved nutrient use efficiency and disease resistance in six years rather than twelve for conventional plant breeding.  We may not be able to produce enough food without synthetic fertilisers and pesticides just yet, but there will be a consistent reduction over the years as our scientists develop new techniques.