The Effect of Calcium and Nitrogen on Reducing Straighthead and Increasing SEED SET RATE on a Silt Loam Soil.

Straighthead disease is a physiological disorder of rice and is the most damaging non-fungal disease. Tts causal factors are still uncertain. This experiment addresses the relationship of straighthead with application of Ca and N into a silt loam soil in greenhouse conditions.

Four varieties, Cocodrie, PB11, PB13, and PB18, were used in this experience. Cocodrie widely used in rice production in Arkansas and as a check of straighthead susceptible variety. Four treatments were applied, Control (CK), N-treatment (4.10 g N /pot), Ca-treatment I (164.25 g Ca/pot), Ca-treatment II (328.50 g Ca/pot), with 8 replications.

The results of ANOVA by SAS program version 12.0, showed that the straighthead and seed set rate were significant different among the treatments of CK, N, Ca_I and Ca_II for all varieties (p<0.0001). N can reduce straighthead symptom by 1-2 scores, and Ca greatly reduced straighthead symptom up to 5 scores for the four varieties. N and Ca both greatly increased the seed set rate for all varieties and Ca tend to increase the seed set rate more than N. In general, the application of N can reduce Straighthead and increase the seed set rate, while the application of Ca can further reduce the straighthead and increase the seed set rate of rice on a Silt Loam soil.

The root lengths of 30 days old root system were analyzed by Root Image Processor Win Rhizo 2012b and SAS program version 12.0. The results showed that the total root length were significant different among the treatments of CK, N, and Ca, and all the p-values were less than 0.05. Ca increased the total root length greatly on all varieties. N only increased the root length on PB 18 when compared with CK, and did not show difference for Cocodrie, PB 11 and PB 13.