SS01 A STUDY OF THE ORGANIC MATTER CONTENT OF MALTESE SOILS
 

Nine different soil series, from different parts of the Maltese Islands, together with an anthropogenic soil from a greenhouse were sampled. Soil level of aggregation and gravel content were measured using dry sieving methods in order to obtain a general idea on the structure of the soils. The level of organic matter was investigated using the Walkley Black method analysis for oxidizable organic carbon. Soil pH was recorded using the Electrometric method.
The level of organic matter increased as the loamy nature of a soil increased. Sandy soils with very loose, open structure together with clayey soils with a hard, very compact structure showed the lowest organic matter level. Except for the sandy soil, organic matter level decreased with soil depth. Greatest variations with depth were observed in uncultivated soils.
Cultivation showed a negative effect on organic matter level as soils belonging to the same soil series had less organic matter content when these were under cultivation, The addition of farm yard manure produced no statistically significant increase in soil organic matter level after a five month period from its application.
A negative correlation was observed between the level of soil organic matter and soil pH.
Research  Worker: Antoine Sacco
Project Supervisor: Prof. Anthony Scicluna-Spiteri
 

SS02 BORON – AN AGRO-ENVIRONMENTAL CONCERN

Boron is an important micronutrient in plant nutrition. It is essential at low concentration, becoming toxic at higher concentration, producing marked yield decrement. The range between deficient and toxic concentration levels is narrow and an understanding of boron sources and reactions in soils is necessary.
Boron is naturally present in most waters; including SASTP treated effluent. Irrigation water containing acceptable levels of boron may not induce toxicity immediately. The soil matrix adsorbs a fraction and the remaining portion is held in the soil solution. If use of boron containing irrigation water continues, the boron concentration in the soil solution may eventually equal that in the irrigation water. The soil matrix will not be able to adsorb increased amounts, with the potential danger that boron in solution eventually increasing in concentration to a level that is toxic to seedlings and boron sensitive agricultural products in general.
The study evaluated boron concentration in different matrices; soil, sewage treated effluent, rainwater, drinking water and compost. A significant total boron concentration difference between the area irrigated with sewage treated effluent (Area 1) and area not irrigated with such effluent (Area 2). Though the treated effluent was thought to be the cause of this marked difference, the sources of boron were found to include drinking water together with detergents and other boron containing products that end up in the sewage system.
The publication of standardisation orders on detergents and products that have the potential of being discharged into the sewage system, without the appropriate market and scientific research is potentially dangerous. Efforts should be made to obtain the necessary derogation against the full liberalisation of product importation so as to retain and improve the ban on the prevention of importation of boron containing detergents and products that end up in the sewage system. The study also sets future boron evaluation possibilities.
Research  Worker: Ray Camilleri
Project Supervisor: Prof. Anthony Scicluna-Spiteri
 
SS03 HEAVY METALS IN SOILS AMENDED BY COMPOSTED MUNICIPAL WASTE
 

A study was carried out to investigate possible increased availability of Zn, Cu, Ni, Pb and Cd from Municipial waste compost used as a soil conditioner in local soils.
Three metal fractions were selected representing the immediately available (aqueous and exchangeable) and the potentially available (organically- or carbonate-bound) metal species. A comparative study with regards to actual crops grown in composted and control fields was carried out to identify possible variances in uptake. Trends for each metal over a time period just following compost application, together with a speciation experiment for the aqueous metal fraction before and after composting were two other factors investigated in this study.
It appears that significant differences existed between metal availabilities in composted and control fields for the aqueous and exchangeable fractions. Significant differences in Potato tissue metal levels were also evident, but levels were below phyto- or zoo- toxic levels.
In contrast to the other metals, temporal variations in Cu fraction appeared to give a different trend for both the aqueous and exchangeable fractions in contrast to the other metals. The speciation experiment indicated that Cu exists mainly as organic species in the aqueous soil solution, while the other metals, except for Ni are mostly present as free ions.
Overall it appears that with a good quality compost and farmer management practices, the organic product should not be considered as being hazardous with regards to metals from both a phyto- and zoo - toxic point of view.
Research  Worker: Jonathan Vella
Project Supervisor: Dr. Tonio Desira Buttigieg
 

SS04 WATER HOLDING CAPACITY IN MALTESE SOILS

The objective of this dissertation was to find the soil water holding capacity of the four different types of Maltese soils, from different parts of the Maltese Islands. Soil samples at different depths were taken regularly and the moisture level was found in each case by drying the soil and calculating the percentage water content in each case. Once the moisture level stopped rising then the water holding capacity of that particular soil was found.

The water holding capacity of the soil increased as the percentage clay in the soil increased. On the other hand as the percentage sand increased, the water holding capacity decreased. Due to the differences in rainfall in the four sites, a rain gauge was placed in each field.

 Once the water holding capacity of each soil was found then one could calculate the maximum volume of water that can be held by the soil in that particular field, in order to prevent drainage of excess water.

 Factors which affect the water holding capacity of a soil were also discussed and these include organic matter, gypsum etc. In fact the addition of organic matter to the soil is one very important way of increasing the soil water holding capacity.

Research  Worker: Kevin Galea
Project Supervisor: Prof. Anthony Scicluna-Spiteri

  BACK TO RESEARCH