TOOL TIME
A simple way to examine your soil structure BY VO THE TRUYEN | REGIONAL DEVELOPMENT OFFICER, VEGETABLESWA
TOOL
EXAMINING SOIL FERTILITY
WHAT DOES IT DO
EDUCATING GROWERS TO TEST SOIL STRUCTURE
WHO WOULD USE IT
ALL GROWERS
THE COST
FREE
MORE INFORMATION
TRUYEN.VO@VEGETABLESWA. COM.AU
FIGURE 1 SOIL PARTICLES TO FORM SOIL AGGREGATES AND THE ARRANGEMENT OF SOIL AGGREGATES TO FORM SOIL STRUCTURE
30
WA Grower WINTER 2020
Soil particles (sand, silt, clay, organic matter)
SOIL FERTILITY IS examined by three main things — soil structural, chemical and biological properties. With increasing cropping intensity, soils of vegetable farms are becoming more vulnerable to the threat of deterioration which make soils become unable to sustain good productivity. The problems are usually unseen below ground and difficult to assess properly, many fail to put them right. This article outlines vegetable growers with basic knowledge of soil structure and a simple way to examine it before providing guidance on how a better soil structure can be achieved and then maintained in the next articles. Soil structure is defined as the way the primary soil particles (sand, silt and clay) are combined and arranged with other solid soil components (organic matters, soil fauna) to form clumps or aggregates. The size, shape and arrangement of these soil solids and the spaces between them influences the soil’s capacity to retain and transmit air, water, organic and inorganic substances, and its ability to support root growth and development (Figure 1). Good soil structure is vital for sustainable agriculture. It limits gaseous exchange rates, for instance the gaseous form of soil fumigants in the treated soil profile. In the field trial on tomatoes and capsicum, the measurement of the biocidal breakdown
Soil aggregate
product of Metham sodium in the case of applications via strickle irrigation was higher on the upper 15cm than at 25cm, and 15–20 times lower at the edge than in the middle of the growing bed1. These greatly reduce the efficacy of soil fumigation practice to kill soil borne pests and weeds. The soil structure influences the movement and storage of water, soil temperature, respiration and development, nutrient cycling, resistance to structural degradation, and supports biological activity. For example, cracks between aggregates that are larger than 0.2mm can be seen. These pores will allow air movement, rooting and drainage. Cracks smaller than this only hold water or fertigation liquid due to capillary force, they don’t drain2.
Soil structure
