Effect Of Nitrogen Fertilizer On Canopy Properties, Sheath Blight Disease Severity And Yield Of Super Rice

It is important for constructing a productive canopy and achieving super highyield in super rice production to study rice canopy properties, yield, and disease underdifferent nitrogen fertilizer application. Field experiment was conducted with thevariety of Liangyou0293 in 2006 at farmer's field in Yong'an town, Liuyang County.The objectives were to (1) to determine the differences in canopy characteristics,microclimate inside canopy and sheath blight infestation among the canopies withdifferent fertilizer nitrogen (N) rates; (2) to investigate the relationship among riceyield, canopy characteristics and disease infestation. The main results of the study arelisted below:1. Significant differences in plant height (PH), tiller number (TN), leaf area index(LAI), aboveground total dry weight (TDW), and crop growth rate (CGR) among Ntreatments. Higher N gave a larger canopy with higher PH, TN, LAI and TDW. Therewere significant conic correlations between grain yield and LAI, PH, TN, TDW, andCGR.2. The temperature (T) and relative humidity (RH) within the canopy wererecorded by HOBO dataloggers. The daily maximum T (Tmax) and the dailyminimum RH (RHmin) varied most among the treatments. The day T and day RHwithin canopy decreased and increased respectively as N level increased. Nitrogenlevel showed significant negative correlations with Tmax and positive correlationswith RHmin.3. There was significant difference in SHBI among N treatments. DS and SHBIhad positive and significant linear correlations with nitrogen dosages. The effect offungicide for sheath blight control increased as N level added.4. The nitrogen use efficiency (NUE) had a negative relationship with N level,and elevated when fungicide was used for controlling sheath blight disease.5. There was significant conic correlation between grain yield and N level. Theoptimum N level for highest yield (10.8 t/ha) was 220 Kg/ha. The yield gap betweenfungicide and non-fungicide application was enlarged as N level increased, which showed the importance of disease control in high-yielding hybrid production.6. Site-specific Nitrogen management (SSNM) obviously decreased sheath blightdisease severity indexes, largely reduced N fertilizer amounts, and kept a higher yield.It is a high yielding, disease resistant, low cost and environment protective fertilizerapplication method and is valuable for popularizing in super rice production.