Root growth and crop yield of two varieties of wheat grown under differing irrigation regimes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University
Root growth and crop yield of Gamenya, a standard height variety, and Karamu, a semi-dwarf, spring wheat were compared under 3 irrigation regimes: daily watering; infrequent (fortnightly) watering; and sub-irrigation, where water was introduced into the soil profile at 40cm, the plots being protected from rainfall. Root growth and development were similar between varieties apart from an indication that the Karamu root system was more extensive at depth. The three irrigation treatments grew distinctly different root systems which was probably due partly to soil compaction differences between the treatments rather than the spatial distribution of the soil water supply. Karamu outyielded Gamenya because of a higher grain weight per ear due to higher floret viability and greater grain weight. Yield differences between irrigation treatments, where the infrequently irrigated treatment was superior, was due to ear population differences related to the differing root systems. With daily irrigation Gamenya used more water, due possibly to the lower leaf water potentials developed in the crop. An inverted water potential difference between the ear and the flag leaf was observed during the middle of the day.