Although Britain depended on imports for over two thirds of its annual wheat, it was not initially affected by war. Germany's use of unrestricted submarine warfare in 1915 and 1916, and again from February 1917, resulted in massive losses of food imports to Britain. This reduction in imports was compounded by an earlier decision by many British farmers not to allow land to lie fallow on rotation, which in the long term decreased the productivity of agricultural land. In addition, a poor harvest in the US further reduced food imports and shortages became commonplace from 1915.
The President of the Board of Agriculture tried unsuccessfully to persuade Cabinet to impose price controls in March 1916. In November, a memo from the Secretary of State for War calling for 'an immediate imposition of agricultural controls' demonstrated the desperate nature of the crisis.
The resignation of Herbert Asquith as Prime Minister resulted in decisive change. David Lloyd George's new President of the Board of Agriculture, Rowland Prothero, intervened to an extent never attempted before in the agricultural sector. War Agriculture Executive Committees in each county were given the power to ensure higher productivity, direct the types of crops to be sown, and increase the amount of land under cultivation. Committees had considerable autonomy over their activities and the incentives they set. In addition, minimum prices were guaranteed for produce and minimum wages guaranteed for agricultural labourers. Rents for agricultural workers were also controlled.
The results were dramatic. The acreage of England and Wales under plough increased by 1.75 million acres by 1918 and productivity increased substantially. Sugar and meat were rationed from January 1918. However, bread never had to be rationed, not even during the crisis months of 1917, when the U-boat campaign reached its peak, nor during the German Spring Offensive of 1918.