Aiwhich Weeds Have Roots That Will Compete Most with the Carrots?

HELP

4 Weeds usually seem to grow faster than garden vegetables. The diagram shows some typical weeds and one vegetable.

Tom is trying to grow some carrots in his vegetable patch. Carrots grow best when they are about 10 cm apart.

aiWhich weeds have roots that will compete most with the carrots?

iiWhy will the carrots be affected by these weeds?

biWhich weeds have leaves that will compete most with the carrots?

iiWhy will the carrots be affected by these weeds?

ciSuggest two ways in which Tom could control the weeds.

iiWhich method will be cheapest for Tom?

CORE

2The diagram shows part of a food web based on a field of cabbages, next to a wood.

aiWhy would the farmer want to get rid of the grass and groundsel?

iiSuggest the quickest way that he could do this.

biWhat would happen to the number of starlings and skylarks if both weeds were removed?

iiWhy would this happen?

iiiWhy and how would this affect the number of thrushes?

ivWhy would this affect the cabbages?

cAn organic farmer might leave an unploughed strip all round the edge of the field. Explain why this might help to maintain the food web in its original state.

EXTENSION

4In some USA states the main agriculture is growing grain. This is done in huge fields often up to a kilometre square. All the hedges have been ploughed up to create these fields. Vast amounts of weedkiller are used to improve the grain yields. Vast amounts of fertiliser are spread onto the soil every year. These farms are in a part of the USA that experiences high winds in most years.

aExplain why these USA farms do not use an organic farming method to remove weeds.

bWhy is artificial fertiliser so important for these fields?

ciSuggest what has happened to the number and range of bird species in these parts of the USA, since such large fields were created.

iiWhy has this happened?

iiiThe number of small, seed-eating rodents such as field mice has increased during the same period. Suggest why this has happened.

dSince the large fields were created there has been a major loss of fertile topsoil in most years.

iSuggest a reason why this has occurred.

iiWhat will the farmers have to do now to prevent all the topsoil from being removed?

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