Index: industry.h
===================================================================
--- industry.h	(revision 5968)
+++ industry.h	(working copy)
@@ -8,6 +8,10 @@
 typedef byte IndustryGfx;
 typedef uint8 IndustryType;
 
+enum {
+	INVALID_INDUSTRY = 0xFFFF,
+};
+
 struct Industry {
 	TileIndex xy;
 	byte width; /* swapped order of w/h with town */
@@ -101,6 +105,7 @@
 
 
 void DeleteIndustry(Industry *is);
+void PlantRandomFarmField(const Industry *i);
 
 enum {
 	IT_COAL_MINE = 0,
Index: clear_map.h
===================================================================
--- clear_map.h	(revision 5968)
+++ clear_map.h	(working copy)
@@ -121,11 +121,11 @@
 }
 
 
-static inline void MakeField(TileIndex t, uint field_type)
+static inline void MakeField(TileIndex t, uint field_type, uint16 industry)
 {
 	SetTileType(t, MP_CLEAR);
 	SetTileOwner(t, OWNER_NONE);
-	_m[t].m2 = 0;
+	_m[t].m2 = industry;
 	_m[t].m3 = field_type;
 	_m[t].m4 = 0 << 5 | 0 << 2;
 	SetClearGroundDensity(t, CLEAR_FIELDS, 3);
Index: clear_cmd.c
===================================================================
--- clear_cmd.c	(revision 5968)
+++ clear_cmd.c	(working copy)
@@ -16,6 +16,7 @@
 #include "table/sprites.h"
 #include "unmovable_map.h"
 #include "genworld.h"
+#include "industry.h"
 
 typedef struct TerraformerHeightMod {
 	TileIndex tile;
@@ -679,9 +680,14 @@
 				SetClearCounter(tile, 0);
 			}
 
-			field_type = GetFieldType(tile);
-			field_type = (field_type < 8) ? field_type + 1 : 0;
-			SetFieldType(tile, field_type);
+			if (_m[tile].m2 == INVALID_INDUSTRY) {
+				/* This farmfield is no longer farmfield, so make it grass again */
+				MakeClear(tile, CLEAR_GRASS, 0);
+			} else {
+				field_type = GetFieldType(tile);
+				field_type = (field_type < 8) ? field_type + 1 : 0;
+				SetFieldType(tile, field_type);
+			}
 			break;
 		}
 
Index: openttd.c
===================================================================
--- openttd.c	(revision 5968)
+++ openttd.c	(working copy)
@@ -50,6 +50,7 @@
 #include "settings.h"
 #include "genworld.h"
 #include "date.h"
+#include "clear_map.h"
 
 #include <stdarg.h>
 
@@ -1440,5 +1441,27 @@
 
 	if (!CheckSavegameVersion(27)) AfterLoadStations();
 
+	/* From 31 on we save the industry who made the farmland.
+	 *  To give this prettyness to old savegames, we remove all farmfields and
+	 *  plant new ones. */
+	if (CheckSavegameVersion(31)) {
+		Industry *i;
+
+		BEGIN_TILE_LOOP(tile_cur, MapSizeX(), MapSizeY(), 0) {
+			if (IsTileType(tile_cur, MP_CLEAR) && IsClearGround(tile_cur, CLEAR_FIELDS)) {
+				MakeClear(tile_cur, CLEAR_GRASS, 3);
+			}
+		} END_TILE_LOOP(tile_cur, MapSizeX(), MapSizeY(), 0)
+
+		FOR_ALL_INDUSTRIES(i) {
+			uint j;
+
+			if (i->xy == 0) continue;
+			if (i->type == IT_FARM || i->type == IT_FARM_2) {
+				for (j = 0; j != 50; j++) PlantRandomFarmField(i);
+			}
+		}
+	}
+
 	return true;
 }
Index: saveload.c
===================================================================
--- saveload.c	(revision 5968)
+++ saveload.c	(working copy)
@@ -30,7 +30,7 @@
 #include "variables.h"
 #include <setjmp.h>
 
-const uint16 SAVEGAME_VERSION = 30;
+const uint16 SAVEGAME_VERSION = 31;
 uint16 _sl_version;       /// the major savegame version identifier
 byte   _sl_minor_version; /// the minor savegame version, DO NOT USE!
 
Index: industry_cmd.c
===================================================================
--- industry_cmd.c	(revision 5968)
+++ industry_cmd.c	(working copy)
@@ -753,6 +753,17 @@
 		}
 	END_TILE_LOOP(tile_cur, i->width, i->height, i->xy);
 
+	if (i->type == IT_FARM || i->type == IT_FARM_2) {
+		/* Remove the farmland and convert it to regular tiles over time */
+		BEGIN_TILE_LOOP(tile_cur, MapSizeX(), MapSizeY(), 0) {
+			if (IsTileType(tile_cur, MP_CLEAR) && IsClearGround(tile_cur, CLEAR_FIELDS)) {
+				if (_m[tile_cur].m2 == i->index) {
+					_m[tile_cur].m2 = INVALID_INDUSTRY;
+				}
+			}
+		} END_TILE_LOOP(tile_cur, MapSizeX(), MapSizeY(), 0)
+	}
+
 	i->xy = 0;
 	_industry_sort_dirty = true;
 	DeleteSubsidyWithIndustry(i->index);
@@ -801,7 +812,7 @@
 	} while (--size);
 }
 
-static void PlantFarmField(TileIndex tile)
+static void PlantFarmField(TileIndex tile, uint16 industry)
 {
 	uint size_x, size_y;
 	uint32 r;
@@ -841,7 +852,7 @@
 	BEGIN_TILE_LOOP(cur_tile, size_x, size_y, tile)
 		cur_tile = TILE_MASK(cur_tile);
 		if (!IsBadFarmFieldTile2(cur_tile)) {
-			MakeField(cur_tile, field_type);
+			MakeField(cur_tile, field_type, industry);
 			SetClearCounter(cur_tile, counter);
 			MarkTileDirtyByTile(cur_tile);
 		}
@@ -858,14 +869,19 @@
 	SetupFarmFieldFence(tile + TileDiffXY(0, size_y - 1), size_x, type, AXIS_X);
 }
 
+void PlantRandomFarmField(const Industry *i)
+{
+	int x = i->width  / 2 + Random() % 31 - 16;
+	int y = i->height / 2 + Random() % 31 - 16;
+
+	TileIndex tile = TileAddWrap(i->xy, x, y);
+
+	if (tile != INVALID_TILE) PlantFarmField(tile, i->index);
+}
+
 static void MaybePlantFarmField(const Industry *i)
 {
-	if (CHANCE16(1, 8)) {
-		int x = i->width  / 2 + Random() % 31 - 16;
-		int y = i->height / 2 + Random() % 31 - 16;
-		TileIndex tile = TileAddWrap(i->xy, x, y);
-		if (tile != INVALID_TILE) PlantFarmField(tile);
-	}
+	if (CHANCE16(1, 8)) PlantRandomFarmField(i);
 }
 
 static void ChopLumberMillTrees(Industry *i)
@@ -1474,14 +1490,7 @@
 	i->height++;
 
 	if (i->type == IT_FARM || i->type == IT_FARM_2) {
-		tile = i->xy + TileDiffXY(i->width / 2, i->height / 2);
-		for (j = 0; j != 50; j++) {
-			int x = Random() % 31 - 16;
-			int y = Random() % 31 - 16;
-			TileIndex new_tile = TileAddWrap(tile, x, y);
-
-			if (new_tile != INVALID_TILE) PlantFarmField(new_tile);
-		}
+		for (j = 0; j != 50; j++) PlantRandomFarmField(i);
 	}
 	_industry_sort_dirty = true;
 	InvalidateWindow(WC_INDUSTRY_DIRECTORY, 0);