Effects of Potash on Baldo, Lagrue and Bengal Rice
Gene Stevens, Allen Wrather, Chris Moylan, and Alan Sheckell
Potassium has been shown to reduce susceptibility to diseases such as stem rot, which effects crop lodging. In 1999 and 2000, an experiment was conducted on a low potassium testing soil to study the effects of methods of applying K on rice lodging and yield. Varieties tested were Baldo, Lagrue, and Bengal. Results revealed that the greatest yields occurred with Baldo when potash was applied in split applications at mid-season. On Lagrue and Bengal, yields were the highest when 40 lb K2O was applied preplant.
In Italy, where Baldo was bred, mid-season applications of potash are recommended. Research elsewhere has shown a close correlation between potassium content of the basal part of the rice culm and the breaking strength of the stem. Potassium deficiency in rice decreases the accumulation of starch and cell wall substances that influence stem strength. Studies have shown that potassium fertilization is also effective in increasing resistance to leaf spot, stem rot, and bacterial blight. Lagrue has been reported to be susceptible to kernel smut. Bengal is highly susceptible to brown spot.
Five potassium treatments were tested with three varieties at the Missouri Rice Farm (Table 1). Dry potash was used on the preplant and mid-season treatments Trts 2 and 3. Potassium nitrate was foliar applied on treatment 4. Treatment 5 was included with the same N rate as treatment 4 to be sure that if a response to foliar KNO3 was found we could determine whether it was due to K or N.
Table 1. Potassium treatments on rice.
Trt Description Preplant MS 1/2 IE MS 1/2 IE + 1 wk
------------lb K2O/acre-------------
1 Check 0 0 0
2 Preplant K 40 0 0
3 Midseason K 0 20 20
4 Foliar KNO3 0 10 10
5 Folia urea 0 1.3 1.3
In 2000 we observed 100% lodging in all Baldo treatments (Table 2). Baldo yields were consistently higher when split applications of K2O were applied at mid-season. Results for Lagrue and Bengal showed that the greatest yields occurred when potash was applied preplant, which is consistent with 1999 results.
If one is experiencing potassium deficiency at mid-season, do not be afraid to correct it. Most aerial applicators charge a flat fee for applying any amount of fertilizer less than 100 pounds per acre. With current mid-season N recommendations of 30 lb N/acre at internode elongation + 30 lb N/acre one week later, farmers are only applying 66 lb of urea fertilizer on each trip across a rice field. The treatment in this test with two mid-season potash (62% K2O) applications had 20 lb K2O/acre on each trip. This was 33 lb of potash fertilizer/acre which when mixed with urea made the total fertilizer rate 100 lb per acre on each mid-season application. The net effect is no additional charge to applying K mid-season as long as N is being applied anyway.
Table 2. Effect of potash timing and fertilizer on rice lodging, milling, and yield.
Preplant Mid Mid Variety Lodging Milling Yield Two
season 1/2 season 1/2 Year
IE IE+1 1999 2000 1999 2000 1999 2000 Average
week Head Total Head Total ---bu per acres----
Untreated No No Lagrue 0 0 65 71 67 75 177 243 210
Check Potash Potash Bengal 0 0 68 72 70 74 178 201 190
Applied Applied Baldo 64 100 59 75 67 75 114 107 111
Broadcast No No Lagrue 0 0 66 72 69 76 185 255 220
40lb K2O Potash Potash Bengal 0 0 67 71 71 75 204 216 210
Dry Applied Applied Baldo 71 100 63 74 67 76 102 117 110
Potash
No Broadcast Broadcast Lagrue 0 0 65 71 68 74 184 222 203
Potash 20 lb 20 lb Bengal 0 0 67 73 70 75 193 205 199
Applied K2O Dry K2O Dry Baldo 73 100 63 74 68 76 120 119 120
Potash Potash
No Foliar Foliar Lagrue 0 0 66 71 68 74 176 210 193
Potash 10lb K2O 10lb K2O Bengal 0 0 67 71 69 74 187 188 188
Applied KNO3 KNO3 Baldo 29 100 59 77 64 76 115 114 115
No Foliar 1.3 Foliar 1.3 Lagrue 0 0 64 70 69 73 172 250 211
Potash lb N Urea lb N Urea Bengal 0 0 67 73 70 75 183 195 189
Applied Baldo 61 100 60 73 71 76 101 116 109
Foliar urea was applied at same N rate as N supplied from KNO3 in treatment above. Leaf samples were collected and analyzed for percent K content before applying midseason dry and foliar K treatments.
This experiment funded by the Missouri Rice Research and Merchandising Council.