Productivity and efficiency

Net production / kJm^-2year^-1 = gross production - respiratory losses

• Net production: energy available to pass on to next trophic level

• Gross production: total solar energy that plants convert to organic matter

• Respiratory losses: plants use 20-50% of their energy for respiration

How to work out energy in biomass:

• Bomb calorimeter

• Dry out the biomass

• Burn it to release the chemical energy as heat energy and record it

How can humans (farmers) maximise efficiency (and why)?

For producers, arable farmers can adopt these methods:

• Greenhouses - artificial light, temperature

• Optimising planting distances

• Irrigation

• Fertilisers

• Selective breeding

• Fungicides/pesticides

• Fencing to exclude grazers

• Ploughing and herbicides to kill weeds

• Plant crops that store energy in edible form e.g. seeds, fruit, tubers

Livestock farmers can adopt these methods for primary consumers (grazers):

• Use of good quality feeds/food supplements

• Use antibiotics and vaccines to reduce disease

• Control predation with fencing or indoor animal husbandry

• Reduce competition for grazing e.g. rabbits, deer

• Indoor husbandry to reduce energy loss from movement or getting cold outside