The oppropriate humidity level for crop cultivation

[renad_kassem]

?What is the oppropriate humidity level for crop cultivation
for soil and for the air

[GES DISC - jimacker]

Thank you for your question. We are working on providing a response and will reply shortly.

[GES DISC - jimacker]

Regarding your question regarding appropriate humidity and soil moisture levels for crop cultivation, this is a complex question to answer, as there are many different types of crops which have different optimum conditions for their cultivation. Growing conditions and growing seasons for crops vary widely. Agricultural scientists have also developed crops suitable for wetter and particularly drier conditions, such as arid regions near deserts.

Crops also vary in terms of the depth that their roots penetrate to acquire water for growth, with plants in arid regions generally having longer roots with deeper penetration than in wetter regions.

So, in order to determine what conditions are suitable for crop cultivation, it would be necessary to know what types of crops are being considered.

What the GES DISC can provide are data variables that can be used to assess conditions, both current and historical, that can affect crop cultivation. Humidity is one such variable, which can be obtained directly from satellite instruments or from models. However, humidity is not as directly related to plant growth and viability as a related variable, which is vapor pressure deficit (VPD). This may also be referred to as the water vapor pressure saturation deficit. VPD is directly related to evapotranspiration, and can be calculated as a function of temperature and humidity. (Tables of VPD for various combinations can be found online, but we cannot provide links to them as they are from commercial sources.) Studies have indicated that increasing VPD causes reduction in plant growth, notably in tropical regions where higher temperatures and humidity are expected.

This paper is an example:
• Anja Nölte et al. Sharp decline in future productivity of tropical reforestation above 29°C mean annual temperature. Sci. Adv.9,eadg9175(2023). DOI:10.1126/sciadv.adg9175

The GES DISC has humidity and temperature data variables and we will briefly describe how to use them to calculate VPD in a subsequent post. Evapotranspiration is also available.

Regarding soil moisture, the GES DISC does not have remotely sensed soil moisture, which can be acquired from the Soil Moisture Active Passive (SMAP) mission, https://smap.jpl.nasa.gov/. The GES DISC does have soil moisture data in the Land Data Assimilation System (LDAS) data products, including the Global LDAS (GLDAS) and North American LDAS (NLDAS). These data products provide surface and deeper layer soil moisture, including the important root zone soil moisture variable which is important to agriculture.

Our Giovanni data system (link) can be used to assess and quickly plot data variables of interest, including those mentioned above. I am providing links to the system which include three common keyword search terms so that you can assess these data variables.

https://giovanni.gsfc.nasa.gov/giovanni/#service=TmAvMp&starttime=&endtime=&dataKeyword=humidity
https://giovanni.gsfc.nasa.gov/giovanni/#service=TmAvMp&starttime=&endtime=&dataKeyword=Evapotranspiration
https://giovanni.gsfc.nasa.gov/giovanni/#service=TmAvMp&starttime=&endtime=&dataKeyword=soil%20moisture

[GES DISC - jimacker]

For crop cultivation a useful term to compute is the vapor pressure deficit ([url=ttps://en.wikipedia.org/wiki/Vapour-pressure_deficit]https://en.wikipedia.org/wiki/Vapour-pressure_deficit[/url]). The simplest way to calculate the vapor pressure deficit is to use the relative humidity and temperature, both of which are available from our Atmospheric Infrared Sounder (AIRS) datasets. First use the temperature to solve for the saturated vapor pressure (es) using Teten’s equation (https://www.weather.gov/media/epz/wxcalc/vaporPressure.pdf). Then with the relative humidity solve for the vapor pressure (e) and take the difference (es – e) to find the vapor pressure deficit for the air.