I would like to reflect on a very informative international seminar “Weather stations. Increasing the quality and quantity of fruit and vegetable harvests while reducing costs”, which was organized by jointed FAO/EBRD Project on August 30, 2023.
During the event, participants asked questions about the configuration of weather stations and possibilities of purchasing so-called modules, that is, programs that interpret information.
The configuration of weather stations depends on the purpose of use
If we would like to to know about weather conditions for spraying, then it is sufficient to determine the wind speed, air temperature and relative humidity, and a dew point temperature. To do this, it is enough to purchase an entry-level weather station.
If we want to use water more efficiently for irrigation, we will additionally need readings of soil moisture at different depths. This depth depends on the crop being grown and the depth of placement of the bulk of the plant’s root system. On farms with a large variety of crops, the number of soil sensors should correspond to the number of crops. It is also advisable to install separate soil moisture sensors in each zone of the field with irregular topography. If soil moisture sensors are for some reason unavailable to the farm, at least a precipitation sensor and a program for calculating the evapotranspiration coefficient are required.
In regions with a risk of soil salinity, it is important to know the EC readings (electrical conductivity, it reflects the total salt concentration). The higher the soil moisture, the lower the EC and vice versa. However, EC can increase immediately after the application of mineral fertilizers. The soil pH indicator, of course, is important, but it does not change much during the season. In any case, watering does not affect it, but the composition of the applied fertilizers can affect it, but locally, only in the root zone. If changes appear on the pH graph after watering, this means that the watering solution is getting on the sensor.
If we want to more effectively combat infections such as apple scab (Venturia inaequalis), potato late blight (Phytophtora infestans), grape mildew (Erysiphe necator formerly known as Oidium), then information about soil moisture becomes irrelevant, but it is important to know leaf moisture, in addition to temperature and humidity and precipitation. In turn, for modules that predict the development of a population of a particular insect (pests or predators), leaf moisture is not required.
For more accurate planning of sowing, it is useful to know the temperature of the soil. It should also be known when planning harvesting. For example, carrots harvested at soil temperatures below 12°C can’t be stored well for a long time, as they become more infected during the harvesting process. Thus, it is better to sell such batches quickly. Some soil infections (Fusarium spp., cruciferous clubroot Plasmodiophora brassicae) infect plant roots to a greater extent at soil temperatures above 15°C. Knowing the current soil temperature helps to plant or sow in time and reduce the risk or prepare for protective measures.
Information about the solar radiation is necessary for precise watering of plants in greenhouses and nethouses, especially when grown in a small volume of substrate. This information also makes it possible to predict the coloring of fruits in orchards. The solar radiation is a term widely used in modern greenhouse production, because weather stations have been used in high-tech greenhouses for more than 30 years, including in Ukraine, Georgia, Uzbekistan, Latvia, and Moldova.
And although some weather stations also provide information about the phase of the moon, in practical work this data may only be required in biodynamic agriculture.
So, first we need to decide why we need a weather station, what we want from it, and only then look for a suitable model.
Decision support systems
Growers know that a wormy apple does not mean that no chemicals were used in its cultivation; more often it means that plant protection products were used, but did not work. In order for treatment with plant protection products to be effective, it is important to correctly determine the time of spraying, that is, the moment when the organism we are fighting is most vulnerable. the most suitable chemical and weather conditions suitable for this particular chemical.
Typically, such decisions are made on the basis of experience, and previously made mistakes are often repeated – “we have always done it this way.” Decision support systems are computer programs that use mathematical models of the development of a particular harmful organism, helping to correctly carry out treatment with chemicals. Typically, their use does not reduce the number of treatments performed, since pests continue to develop as long as agro climatic conditions contribute to this. The use of these systems increases the efficiency of treatments, that is, it makes it possible to obtain higher quality products without exceeding the MAL (maximum allowed limit of pesticide residues).
Decision support systems are offered by different companies. Apple growers around the world are familiar with the RimPRO program, but there are other programs available. Typically such systems are offered on a subscription basis. The price of a subscription varies and mainly depends on how much research was required to develop a mathematical model of the development of a particular biological species. This is a hard work that scientists have been doing for years.
At the beginning you manage to do without your own weather station
Decision support systems operate on the basis of mathematical models taking into account actual weather conditions, including the accumulated sum of active temperatures, precipitation, etc., and they also take into account predicted weather conditions. In this case, data from all weather stations in a certain region are used. Therefore, the more weather stations there are, the more accurate the forecast of both the weather and the development of the population of a particular organism. Usually we are talking about harmful organisms, but with the increasing use of biological control in the open field crops, forecasts for the development of predator populations will also be required.
Many small farms cannot (or think they cannot) afford their own weather station, in which case the decision support system makes the calculation based on the available data. This is called a virtual weather station. Of course, such a calculation is not very accurate, but with some experience it is possible to use even such forecasts. For example, “The program promises rain tomorrow morning, which means it will start in the afternoon, and before that we will have time to apply fertilizer”.
Role of consultants
The program calculates forecasts for the development of populations of harmful organisms – infections or pests – taking into account regularly entered observational data. In an orchard, this may be the results of inspection of pheromone traps, in vegetable fields – the results of visual observations of plants. Both the degree of damage to individual plant organs (usually leaves) and their distribution are important. That is, is the entire leaf blade affected or just a few spots and is there one such plant in the field or are there many of them (how many?). It is precisely at this point that the subjective assessment of the observer plays a significant role, despite the fact that he must use the guidelines proposed by the company that developed the program. Damage that one observer would rate as a five on a scale of ten, another might rate as a three, since “they’ve seen worse.” Undoubtedly, once drone observations become common practice, the accuracy of forecasts will increase significantly, because the analysis of digitized images is much more objective.
It is necessary to enter data into the program about all treatments performed – date, product, its dose, amount of spraying solution used. This takes time, but it automates the maintenance of field history, which is especially convenient during inspector visits. And it is easier to determine the harvesting period that corresponds to all the waiting periods for the applied chemicals. This is important not only for GlobalG.A.P., but also for obtaining products that comply with the maximum allowed limits of all chemicals used.
Another problem of small farms is that there is often no one to carry out observations. The owner is forced to devote a lot of time to supply issues, product sales, communication with regulatory authorities and other things, so he gets directly into the field in fits and starts, only to carry out the necessary work.
The programs present their forecasts in the form of graphs, and this is where the hard part begins. Not every farm owner, and not even every agronomist, is able to understand what the graphs are telling him. Some programs comment on their recommendations, for example, “treatment with systemic chemicals is necessary,” “treatment with contact chemicals is recommended,” “treatment is not advisable.” These recommendations take into account both the stage of insect development or the extent of infection, and the weather forecast for the next 5-7 days.
However, not all decision support systems make such recommendations, and in this case, consultation with a specialist is necessary. In a number of countries, this service is actively offered by the Syngenta company; of course, its specialists recommend hemicals from this company to carry out the necessary treatments. In other countries, including Latvia, plant protection specialists regularly send recommendations to subscribers of the RimPRO program based on forecasts made by the program. We can say that they translate these forecasts into a language that the grower can understand. In this case, experts offer chenicals not from just one company, but the most effective (in their opinion) available on the market.
This approach seems more objective, but the skills of the consultants themselves are important. However, it is precisely firms offering professional, technological consultations that can significantly speed up the application of various decision support systems in orchards, vineyards and vegetable fields. And for the successful operation of such systems, weather stations will be required.
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