get_fraction_tilled() receives layer_bottom, not layer_top.

samsrabin · Sep 18, 2023 · 77d0c7d · 77d0c7d
1 parent c0d8784
commit 77d0c7d
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Showing 2 changed files with 15 additions and 9 deletions.
diff --git a/src/soilbiogeochem/TillageMod.F90 b/src/soilbiogeochem/TillageMod.F90
@@ -247,29 +247,35 @@ subroutine get_tillage_multipliers(tillage_mults, idop)
   end subroutine get_tillage_multipliers
 
 
-  function get_fraction_tilled(layer_top, layer_thickness, max_tillage_depth_gft) result(fraction_tilled)
+  function get_fraction_tilled(layer_bottom, layer_thickness, max_tillage_depth_gft) result(fraction_tilled)
     ! !ARGUMENTS
-    real(r8), intent(in) :: layer_top       ! Soil layer interface depth (zisoi)
+    real(r8), intent(in) :: layer_bottom    ! Soil layer interface (between j and j+1) depth (zisoi)
     real(r8), intent(in) :: layer_thickness ! Soil layer thickness (dzsoi_decomp)
     real(r8) :: max_tillage_depth_gft ! Maximum tillage depth
+    ! !LOCAL VARIABLES
+    real(r8) :: layer_top
     ! !RESULT
     real(r8) :: fraction_tilled ! Fraction of this layer that's within the tillage depth
 
+    ! If the top of the layer is below the max tillage depth, do not till.
+    layer_top = layer_bottom - layer_thickness
     if (layer_top > max_tillage_depth_gft) then
         fraction_tilled = 0._r8
         return
     end if
 
+    ! Handle zero-thickness layers. This may not be necessary.
     if (layer_thickness == 0._r8) then
-        if (layer_top <= max_tillage_depth_gft) then
+        if (layer_bottom <= max_tillage_depth_gft) then
             fraction_tilled = 1._r8
         else
             fraction_tilled = 0._r8
         end if
-    else
-        fraction_tilled = max(0._r8, min(1._r8, (max_tillage_depth_gft - layer_top) / layer_thickness))
+        return
     end if
 
+    fraction_tilled = max(0._r8, min(1._r8, (max_tillage_depth_gft - layer_top) / layer_thickness))
+
   end function get_fraction_tilled
 
 

diff --git a/src/soilbiogeochem/test/tillage_test/test_tillage.pf b/src/soilbiogeochem/test/tillage_test/test_tillage.pf
@@ -23,12 +23,12 @@ contains
     integer  :: j                 ! Soil layer
     real(r8), parameter :: max_tillage_depth = 0.21_r8
 
-    zisoi = [0._r8, 0.01_r8, 0.05_r8, 0.1_r8, 0.5_r8]
-    dzsoi_decomp = [zisoi(2) - zisoi(1), &
+    zisoi = [0.01_r8, 0.05_r8, 0.1_r8, 0.5_r8, 1._r8]
+    dzsoi_decomp = [zisoi(1) - 0._r8, &
+                    zisoi(2) - zisoi(1), &
                     zisoi(3) - zisoi(2), &
                     zisoi(4) - zisoi(3), &
-                    zisoi(5) - zisoi(4), &
-                    0.5_r8]
+                    zisoi(5) - zisoi(4)]
 
     @assertEqual(1._r8,    get_fraction_tilled(zisoi(1), dzsoi_decomp(1), max_tillage_depth))
     @assertEqual(1._r8,    get_fraction_tilled(zisoi(2), dzsoi_decomp(2), max_tillage_depth))