Why did the Germans suffer starvation during World War I?

In WW1 Britain and Germany tried to starve each other into surrender by a naval blockade. In the longer run the British Navy was more successful at this ... Germany's agony was prolonged by its (for the time) modern and sophisticated chemical industry that enabled it to produce vast quantities of articial fertilizers, which raised the yield per hectare substantially. Without the work of Fritz Haber, Germany would probably have had to surrender much earlier.