Argentina’s Agtech S4, developer of technology to reduce climate risk in agriculture, in its August Climate Report, prepared by Agronomist Carlos di Bella.
The main conclusion of the report is that there will be fewer frosts as a result of the increase in average minimum temperatures. This has a direct impact on our main winter crop, wheat.
A comparison with past data shows a trend towards an increase in the minimum average temperature, which would extend over the next 20 years, according to current climate forecasting models.
It is probable that in the future we will have more moderate average temperatures and more limited extreme values, especially in the dates of last frosts.
The increase in the flooded area is reducing the daily thermal amplitude and increasing the frost free period.
In short, even with a high variability in the intensity and dates of frost, it would be feasible that in the coming years the average minimum temperatures are higher.
How do frosts impact our main winter crop, wheat? Frost (< 0 ºC) has a very important impact on wheat production. Although they can cause damage in both vegetative and reproductive stages, it is in the latter where the greatest damage occurs mainly associated with sterility and abortion of formed grains (Barlow et al. 2015). The critical temperature for the damage to begin would be 2 hours of exposure to values between -4 and -6 ºC. For each degree of temperature decrease from -4 ºC up to 100% of the production could be lost. The relevance of this phenomenon is very important since wheat, with a world production of approximately 600 million tons, represents the third largest crop globally.
Is it possible to adapt to these situations?
Many try to adapt by changing the sowing date or by using crops that are more resistant to low temperatures. However, these decisions are made by analysing data for periods of the year of enormous variability and using very small time series as baseline information.
Both aspects inevitably affect the accuracy of the estimates. In fact, many times management decisions are based on very extreme situations that do not represent the enormous gradient of possibilities that could actually occur in the field.
How does change in land use and land cover impact frost on a regional scale? A key aspect is the impacts of changes in land use and land cover on the occurrence of frost. Houspanossian et al. (2016) found that flooding in the Pampean Region in recent decades reduced the incidence and length of the frost free period by at least two months. These results show the effect of the presence of large bodies of water on the thermal regime of their surrounding areas (Figure 1).
What is the current trend of the mean minimum temperature analysing past data?
Analyzing trends in past minimum temperatures (SMN 1961-2018), we see an increase in this variable in almost all of our territory, both in winter and in spring.
When consulting the information provided by the Agroclimatic Information Centre – CIAg (https://www.agro.uba.ar/heladas/), in terms of the average dates of first (FPH) and last frosts (FUH), our Pampas region oscillates between 1 April and 15 July in the first case (FPH) and between 15 July and 14 November for the second (FUH).
What are the minimum temperature forecasts for the coming decades?
Looking at the long-term forecasts, there is a general trend towards an increase in the minimum average temperature over the next 60 years. Likewise, if this monthly disaggregated information is taken for the next 20 years, the trend is similar: a marked reduction in the variability of the minimum temperature on the average dates of the last frosts (World Bank Group 2018).
Figure 1: Average frost-free period for the localities of Anguil (Interior not flooded), Pehuajó (Interior flooded) and Mar del Plata (Coastal not flooded) for periods with flooding (Grey bar: Years 1973, 1985-1988, 1997-2003, 2012) and periods without flooding (Black bar: Rest of the years). The duration of the frost-free period is indicated on the left of the bars. Adapted from Houspanossian et al.
– Barlow, K.M., B.P. Christy, G.J. O’Leary, P.A. Riffkin, J.G. Nuttall (2015). Simulating the impact of extreme heat and frost events on wheat crop production: A review. Field Crops Research, 171, 109-119.
– CIAg (https://www.agro.uba.ar/heladas/)
– Houspanossian, J; Sylvain Kuppel,.; Marcelo Nosetto,.; Carlos Di Bella,.; Patricio Oricchio,; Mariana Barrucand,; Matilde Rusticucci,.; Esteban Jobbágy, (2016). Long-lasting floods buffer the thermal regime of the Pampas. Theoretical and Applied Climatology DOI: 10.1007/s00704-016-1959-7
– National Meteorological Service (NMS) – https://www.smn.gob.ar/clima/atlasclimatico
– World Bank Group 2018 (https://climateknowledgeportal.worldbank.org/country/argentina)
WEATHER REPORT (CARLOS DI BELLA)
In its July 26 monthly report, SMN reported that the ENOS phenomenon is in the WEAK CHILD phase with a 62% probability of transition to Neutral Phase for the August-September-October quarter of the current year.
Taking into account these forecasts for Argentina, most of the rain forecasts for the next quarter are inclined towards a slight tendency to values above normal in the Mesopotamia Region, North Central and N of the province of Buenos Aires (Figure 1). In Brazil, forecasts are less coincidental. Some forecast a higher probability of above-normal precipitation in the S of Brazil; and others below-normal in the Mid-South portion of the country (e.g. Mina Gerais, Goias).
When associating these forecasts with the available products of soil water balance (e.g. USDA- USA) a particular situation becomes evident: Higher probabilities of occurrence, in one sense or another, accompany the availability of water in the soil (higher rainfall where water in the soil is abundant/excessive or lower rainfall in places with water limitations).
Figure 1: Climate forecast for quarter A-S-O 2019 integrating and interpreting climate forecasts from SMN (Argentina), IRI (USA), NME-NOAA (USA), CPTEC (Brazil).
Figure 2: Percentage of water in soil as of July 28, 2019 (USDA Source)