Increasing wheat yields in north-eastern Victoria by liming and deep ripping

Wheat grain yields, dry matter production and yield components were measured in a field experiment in north-eastern Victoria over 5 seasons where lime application and deep ripping had been carried out. The soil at the site was strongly acid (pHw 5.2 at 0-1 0 cm) and had a dense hardpan at 7.5- 17.5 cm depth. Grain yields (control yields 1981-85: 1.34, 0.25, 1.64, 2.36, 2.09 t ha-1) were increased each year by both lime (31-103% range) and deep ripping (11- 41% range), but the application of some lime was necessary to obtain benefit from deep ripping. The increased grain yield was mainly due to more heads per metre of row, although head size and grain weight were also increased by lime treatment. Lime increased the dry matter yield of roots and decreased the top to root dry matter ratio. Deep ripping increased the dry matter yield of roots at depth and also reduced root distortion where the hardpan had been shattered. In a drought season, deep ripping increased grain weight. Root disease was accentuated at the higher rates of lime.