Rice growth and post-rice mungbean in relation to two puddling intensities under glasshouse conditions

The effect of soil puddling on growth of lowland rice (Oryza sativa) and post-rice mungbean (Vigna radiata) was investigated using mini rice beds under controlled glasshouse conditions. Each mini rice bed was approximately 1 m(3) in size. Three different soil types were used: a well-drained, permeable loam; a hardsetting, structurally unstable silty loam; and a medium clay. Rice yields were reduced by low puddling compared with high puddling intensity on the loam but not affected on the heavier textured soils (silty loam and clay). Yield of mungbean was reduced on highly puddle, structurally unstable soil, indicating that puddling should be reduced on structurally unstable soils. Under glasshouse condition where crop establishment was not a limiting factor and plant available water in 0.65 m of soil was 100 mm, mungbean yields of >1 t/ha were achieved. However, under conditions where subsoil water reserves were depleted for the production of vegetative biomass during initial optimal growing condition, grain yield remained well below 1 t/ha.

Soil exploration by sorghum root systems in wide row cropping systems

Wide and ‘skip row’ row configurations have been used as a means to improve yield reliability in grain sorghum production. However, there has been little effort put to design of these systems in relation to optimal combinations of root system characteristics and row configuration, largely because little is known about root system characteristics. The studies reported here aimed to determine the potential extent of root system exploration in skip row systems. Field experiments were conducted under rain-out shelters and the extent of water extraction and root system growth measured. One experiment was conducted using widely-spaced twin rows grown in the soil. The other experiment involved the use of specially constructed large root observation chambers for single plants. It was found that the potential extent of root system exploration in sorghum was beyond 2m from the planted rows using conventional hybrids and that root exploration continued during grain filling. Preliminary data suggested that the extent of water extraction throughout this region depended on root length density and the balance between demand for, and supply of, water. The results to date suggest that simultaneous genetic and management manipulation of wide row production systems might lead to more effective and reliable production in specific environments. Further study of variation in root-shoot dynamics and root system characteristics is required to exploit possible opportunities.