The largest mean responses to nitrogen ranged from 2·1 cwt grain/acre in 1966 (2 cwt N/acre) to 3·6 cwt grain in 1968 (1–5 cwt N/acre). Responses to the largest dressings were increased by dividing them, the increases ranged from 0·2 cwt grain in 1968 to 4·0 cwt grain in 1966.

In 1968 1·5 cwt N applied in late May increased grain yield by 5·5 cwt, more than the response to any other amount applied either to the seed bed or as a divided dressing. Removing the growing point of the plant at the 4-leaf stage promoted tillering but lessened yield by 5·4 cwt grain. Removing the growing point of the plant after flowering increased yield by 2·1 cwt grain in 1966 and lessened it by 1·7 cwt grain in 1967.

CCC (2-chloroethyltrimethylammonium chloride) had no visible effect on growth and lessened yield by 1·9 cwt.

B9 (N-dimethylaminosuccinamic acid) greatly affected growth and shortened stems by as much as 30%, depending on how much and when it was applied.

B9 had inconsistent effects on yield. Without fertilizer nitrogen, it increased yield by 2·5 and 2·6 cwt grain in 1966 and 1968 but decreased it by 2·1 cwt in 1967.

The main effects of B9 on the components of yield were to increase the number of stems and pods/acre and lessen 1000 grain weight. Plants given B9 in 1968 produced half a million more grains/acre than untreated plants. 1·5 cwt N had similar effects to B9 on the components of yield in 1968. Stems and pods/acre were increased, but there was also a small increase in 1000 grain weight. Plants given 1·5 cwt N produced half a million more grains/acre than plants not given N. A further1·5 cwt N lessened number of stems/acre but this was more than compensated for by an increased number of pods/stem, leading to a further increase of 160000 grains/acre. The effects of season were large and exceeded the effects of any of the treatments.