Highly Innovative Technique for soil solarization: a new approach in the Environment Respect (INTER)

Project leaders

Pasquale Mormile, Changrong Yan

Agreement

CINA - CAAS-not in force - Chinese Academy of Agricultural Sciences

Call

CNR-CAAS 2017-2019

Department

Physical sciences and technologies of matter

Thematic area

Physical sciences and technologies of matter

Status of the project

New

Research proposal

1. Introduction
In the last 15 years agriculture in South of Europe and China was marked by the increase of greenhouse productions to obtain vegetables that could be available for customers during all the year. This intensive cultivation means also many problems for soil pathogens that have to be eliminated before new crops. The control of weeds, pests and pathogens in such complex system requests the use of greater amount of fumigants (less effective of methyl bromide meanwhile phased out) and pesticides. On the other hand, the reduction of agrochemical use is one of the major challenges and moreover pesticides applications are not the best technical and economic problem solution due to the concern of customers and the very low residues levels requested by the most important retail organizations. Anyhow, the control of weeds, soil borne fungal pathogens and pests need soil treatments. The increasing public interest toward environment protection and human health prompted the research of agronomic strategies with low requirements of fungicides, fertilizers and herbicides. In this context, the research for alternatives control methods with high efficiency, low cost and limited environmental impact is an urgent requirement for an eco-sustainable agriculture.
The appropriate use of solarization is a nonchemical method that can provide excellent control of soil-borne pathogens in the field, greenhouse, nursery, and home garden. This method consists in covering the soil surface with a thin clear plastic tarp for several weeks to enhance accumulation of heat. The resulting high soil temperatures inactivate some of the soil microbe partially disinfesting the soil. Moreover the efficacy of solarization depends on the duration of soil cover that normally, to be effective, should exceed 50-60 days this influence the possibility of its large diffusion.
1.1 The state of the art about Solarization technique
Soil solarization is a well known agronomical practice used to sterilize the soil by heating it through solar energy. A good solarization is able to increase the soil temperatures at different depths up to eliminate the most part of pathogens accumulated during any crop cycle. This agronomical practice depends strongly on the temperature levels obtained, at different soil layers, during the solarization process. In other words, the higher are the temperatures the bigger is the solarization effect. The traditional solarization practice requires the use of a plastic film, with very good optical and thermal properties, covering the well wet field and a period long enough (4-5 weeks) in order to obtain a satisfying soil sterilization. Nevertheless, this not always is sufficient, mainly in some contests, where the times for solarization are very short and the results, pathogens elimination, are poor or insufficient. Also the use of inadequate plastic film could frustrate a good soil solarization, because the temperatures average levels during the whole period, are under the minimum threshold to eliminate very harmful pathogens, like Nematodes, that we estimated, according to the literature, about 42°C. The solarization technique could spread, not only in the so-called "sunbelt" area but also in many regions around the world, if a further implementation will be able to reduce the application times and, at same time, to increase the soil temperatures at different depths.
2. The idea
2.1 Description
The Proposal is to introduce an highly innovative method which is just an integration to the well known and common solarization method, used in agriculture to sterilize the soils after harvesting. The innovation consists in the use of a biodegradable black liquid to spray on the soil during the solarization practice, able to increase drastically the soil temperature at different depts. It works like the "black body" described in Planck theory: a body able to absorb, in our case, the most part of solar radiation (wavelength from 0,2 to 2,5 micron). From a physical point of view, this means that the soil temperature increases drastically in comparison with the traditional solarization. This guarantees a total sterilization of soil in shorter time. Our research proposal is aimed to study and test the best black materials to use in the next future during the solarization practice. The main features of this innovative product are to use a completely biodegradable black liquid material, easy to use and very cheap. We considered, as heat collector, a biodegradable black liquid, with dissolved carbon black powder, to spray on the soil at the end of irrigation that, according to the protocol for solarizing, is necessary for heat conduction, up to the internal layer of soil (30-40 cm depth). At the end of irrigation, it covers soil with a real thermal plastic film, able to block the IR radiation emitted from soil, in order to confine the most part of heat in the soil. As a consequence, it obtains a huge increasing of temperatures at different depths, during both night and day.

2.2 Cooperation
The activities planned for the joint research program are based on actions performed both in Italy and China, established and managed by the two scientific responsible, who month per month exchange obtained results, information and suggestions about the parallel work. This research work will be object of deepened analysis during the exchange of visits.
The continuous monitoring, of each activity performed in the two countries, is at base of the joint program and it represents an ideal condition to cooperate on common subjects and goals.
In occasion of visits exchanges, it is foreseen apart from exchange ideas and proposals for the activities in progress and for the future, firstly a direct implication of the visiting Chinese researchers to the tests planned year by year.
The final results will be object of a joint plan of dissemination, to the aim to give techno-scientific elements about the use of the new solarization method.

Research goals

The main goal of our proposal is to confirm, the enthusiastic results obtained up to now, and at same time, to improve the biodegradable black liquid employed previously and, finally, to transfer to Chinese partners of CAAS the acquired knowledge, involving, for the planed trials, farmers that need a natural method to sterilize soil without using dangerous chemicals. The scenario, that it will open, could represent a real revolution in agriculture with drastic changes that will have a great impact in the agronomical traditional practice, in the environmental safeguard and in the respect of the human health. Because we expected a confirmation of the positive results obtained up to now, and a further improvement of the new method, thanks to the materials (biodegradable black liquid and solarization film) more performant, we foresee, in two-three years, an enormous increasing of new solarization method and, at same time, a drastic decreasing of fumigation method, both in China and Italy.
According to the expectation, we will have a new solarization method that will guarantee a total soil sterilization, like fumigation but at cheaper costs. On the base of this real and concrete forecast, the main objective of our project is to introduce, both in Italy and China, our innovative soil sterilization practice in agriculture, that respects environment and safeguards human health. Further objective is to disseminate the results of trials in the two countries through different channels.

Last update: 20/04/2024