Subsoil moisture impacts in 2000

November 24, 2020 8:36 PM
Blog Post

A quick review of subsoil moisture during the fall of 1999 and the spring of 2000 shows that subsoil moisture did not recharge much from October 30, 1999 to April 10 of 2000  (table 1).  The five subsoil moisture sites gained from 0.6 to 4.2 inches of moisture during the late fall and early spring.  The locations near Newell and Schaller only gained 0.6 and 2.4 inches of subsoil moisture.  

Table 2 shows the April 11 to September 1 rainfall was almost normal in Milford, Estherville, Spencer and Pocahontas.  However, rainfall at the Sac City and Storm Lake weather reporting stations was 8.4 and 9.5 inches below normal, respectively. 

Therefore, this lack of subsoil moisture and summer rainfall impacted county corn grain yields.  Corn grain yields as reported by USDA NASS were in the 150 bu/a range for several northwest Iowa counties.  However, corn yields for Buena Vista and Sac counties were 136 and 128 bu/a, respectively (table 3).

This information shows that continued dry weather in the spring and summer of 2021 could impact corn and soybean grain yields.  Subsoil moisture levels that are not replenished by early summer make corn and soybean crops become more dependent on summer rainfall.  Summer rainfall in the year 2000 supplied the needed moisture for normal corn and soybean yields in Dickinson, Emmet, Clay, and Pocahontas counties – but not in Buena Vista and Sac counties. 

Table 1.  Subsoil moisture from fall 1999 and the spring of 2000.                         

                                                                       October         spring         April                            

                                                                       30,                 county        10,                   moisture        

County             site                1999 crop        1999              average      2000                 gain                

                                                                        -------inches, plant available moisture---------

Dickinson        Spirit Lake     soybean           1.8                 7.8               4.1                   2.3                  

Emmet            Estherville      corn                 5.5                 7.9               6.6                   1.1                 

Clay                Rossie            soybean           4.3                 7.5              8.5                    4.2                  

Buena Vista    Newell            corn                 3.7                 7.5              4.3                    0.6                 

Pocahontas    Rolfe              corn                 2.0                 7.6              3.9                    1.9        

Sac                 Schaller.         soybean          2.3                 7.7               4.7                    2.4.                              

 

Table 2. Rainfall from April 10 to September 1, 2000.

                        Actual             normal             difference        

                        ------------------ inches ------------------    

Milford             17.0                17.7                 -0.7                 

Estherville       18.6                 17.8                 +0.8            

Spencer           14.7                17.8                 -3.1                 

Storm Lake     10.4                 19.9                 -9.5                 

Pocahontas     18.1                19.1                 -1.0                 

Sac City          10.8                 19.2                 -8.4             

Table 3. County USDA NASS corn, soybean grain yields, 2000.

                                                                                               

County                                      ----bu/a----

Dickinson                                151           46

Emmet                                    156            43

Clay                                        153            49

Buena Vista                            136            38

Pocahontas                            156            43

Sac                                         128.           34

 

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Paul Kassel Field Agronomist in NW Iowa

Paul Kassel provides research based crop production information to area farmers and agribusiness. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include soil survey, crop production, soil ferti...