Today we will discuss precipitation and climate patterns and how they are expected to change.
The crop water balance equation states:
Precipitation (P) + Irrigation (I) = Runoff (R) + Deep Drainage (D) + Evaporation (E)+ Transpiration (T) ± Soil Water Content (∆S).
The water balance equation considers the crop and soil as a box with inputs and outputs, the inputs being P+I and the outputs R+D+ET and ∆S soil water in the root zone a storage component. The components of the water equation are expressed in units of depth (such as inches or cm of water). In the previous issues we discussed R, D, E, T and ∆S and today we will wrap it up with a discussion of our climate with a focus on precipitation, and how it is expected to change in the future.
Annual precipitation averages roughly 40 inches in Pennsylvania, although it varies between regions (Figure 1). Air movement is typically from the west to the east, so clouds will move in that direction most of the time. Orographic effects (lifting and lowering of airmasses when air flows over mountains) cause higher precipitation west and lower precipitation east of the Allegheny mountains, and higher precipitation in the Poconos. The effect of large water bodies can also been seen – Humidity from Lake Erie causes increased precipitation in the northwest, while the effect of proximity to the Atlantic Ocean results in higher precipitation in the eastern part of Pennsylvania.
Precipitation includes snow, hail, and rain and its distribution over the year matters too as any farmer knows, as our soils can only hold so much water to help our crops survive from one to the next precipitation event. Precipitation is relatively evenly distributed over the months of the year, but because it is warmer, the water disappears more quickly in summer
In summary, we are blessed with a humid climate that makes it possible to grow crops without irrigation. But our climate is changing. Winter precipitation is increasing. Summer precipitation is becoming more intense. At the same time temperatures are inching up, causing increased risk of drought in summer. All this means that it only becomes more important for farmers in our region to find ways to get more crop for each drop.
Part 1 – the different components of the water balance and how they are affected by our management.
Part 2 – Increased yield with improved water use efficiency can be achieved by managing several soil properties.