An investigation of buried viable seeds under pastures of varying crop histories

Abstract

It is a common occurrence to find recently ploughed or surface cultivated areas periodically heavily infested with seedlings of various plants. These seedlings have their source in the buried seed populations often surprisingly large in both total numbers and in the number of species. These seeds have been lying in the soil for varying lengths of time and germinate on being given suitable environmental conditions. The severity of the infestation usually varies with the time of the year, often being heavy in certain months, so much so that in some cases the time of sowing of crops or pastures may be dictated by this consideration alone. But whatever efforts may be made to avoid the handicap that weeds present, it will always remain a problem at some period in the rotational life of an area.

The ability of many plant species to reappear in areas recently ploughed is due principally to dormancy of seeds. Hence once land has become clothed with a natural cover of vegetation it is virtually impossible for any agency to destroy it permanently, for many seeds that may shatter on the ground will remain in a dormant state and the small proportion of these that germinate in any year may reach maturity and add more seeds to those already present in the soil.

Samples were taken from fields under pasture for varying periods. Of the six fields examined, one has never been cropped and has been down in pasture for sixty years, while the other five have had different cropping histories. Details are given for the method used in taking core samples with Laboratory procedure in selecting representative samples from bulked soil. Statistical analysis shows the method used in the field was sufficiently accurate. The method used in separating seeds from the soil and subsequent drying, identification and extraction are discussed. Details of the germination techniques used and data showing how the various seed species respond to the different germination methods is given. The buried seeds are classified into arable, arable and pasture and pasture. Between fifty and sixty different species of seeds were identified, most of them were potential weeds. The results show that although most of the buried viable seeds found may be classified as Pasture species, the highest total populations with one exception were from the fields recently sown down after arable cropping. Confirmation has been given to the results of earlier investigations that many grasses must survive by means other than buried seeds.