Information from 2000 Missouri Rice Research Update, February 2001.

Effects of Potash on Baldo, Lagrue and Bengal Rice

Gene Stevens, Allen Wrather, Chris Moylan, and Alan Sheckell

Abstract

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.

Introduction

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.

Materials and Methods

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 KNO30           10               10
 5       Folia urea            0           1.3              1.3

Results

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.

Conclusion

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.

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