Re: Does the type of soil affect the growth rate of a pea plant?

Yes, soil can affect plant growth in many ways. Soil must provide plant roots 
adequate oxygen, water, and mineral nutrients. Soil also provides anchorage for 
the plant to keep it upright. Plant growth suffers if the soil cannot provide 
adequate water, oxygen, mineral nutrients and support. Soils can also restrict 
growth due to toxic levels of pH, mineral nutrients, salinity, pathogens, etc.

Soil effects on plant growth fall into three main categories, physical, 
chemical, and biological. Physical effects include soil aeration, soil water-
holding capacity, soil depth in pot, bulk density, and soil strength (the 
mechanical resistance to root growth). Chemical effects include soil pH, soil 
mineral nutrient levels, and soil salinity. Biological effects include 
pathogens, nitrification bacteria, mycorrhizal fungi, and nitrogen-fixing 
bacteria.

Experiments on soil effects on plants can be done in several ways. One approach 
is to use very different kinds of soils, such as an organic potting soil, a 
white, coarse builder's sand, and a garden loam, and determine how well potted 
plants grow in each one. In this type of experiment, provide optimal water, 
fertilizer, light, and temperature so the soil will be the main limitation to 
plant growth.

Another appraoch is to use the same soil but vary one parameter such as 
irrigation frequency (such as daily, 5 times per day, twice a week), soil pH, 
soil salinity, soil mineral nutrient level, or soil depth. To vary soil depth, 
you would need containers that vary in height but that all contain the same 
volume of soil. Soil aeration increases and water-holding capacity decreases as 
the soil height increases. The bulk density (g dry soil per unit bulk volume) 
can be altered by compressing the soil to different degrees.

Regardless of the experiment, it is desirable to have replication (a minimum of 
three pots per treatment) and measure plant fresh weight and dry weight at the 
end of the experiment. Height alone is not the best measure of plant growth.


References

Hershey, D.R. 1990. Container-soil physics and plant growth. BioScience 40:685-
686.

Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.

Bunt, A.C. 1988. Media and Mixes for Container-grown Plants. Boston: Unwin 
Hyman.


FUNDAMENTALS OF CONTAINER MEDIA MANAGEMENT : PHYSICAL PROPERTIES