Abstract:

Leaf Area Index (LAI) simulation models is an indispensable tool for supporting crop scientific research, population and community growth analysis, and crop management. However, LAI is very difficult to be quantified properly, owing to ecological and varietal factors and temporal variability. Many methods have been developed to quantify LAI and yielded good results, but most of them have different formats with many parameters, which hamper their application. In this paper, an extensively suitable LAI simulation model, y= (a+bx) / (1+cx+dx²), was developed with normalized LAI and crop growth duration data. And by means of which, the specific normalized models y= (0.0134+0.3234x) / (1－2.774x+2.4178x²) for spring maize (r=0.9858**), y= (0.0777+0.0205x) / (1－2.7374x+2.0484x²) for rice (r=0.9865**), and y= (0.0131+0.0035x) / (1－2.4515x+1.5273x²) for winter wheat (r=0.9719**) were established. Compared with other LAI simulation models, normalized LAI dynamic model can not only generate reliable prediction for the evolution of LAI, but also estimate leaf area duration (LAD) and LAI in any period. Once the crop life span and a total leaf area of a crop population in any moment are acquired, the crop LAI and LAD can be estimated easily. From the time of jointing stage, the model could make a good pre-estimation of LAI dynamics with the accuracy of 1.050, 1.0357, and 1.1168 and the precision (R²) were 0.8728, 0.9270, and 0.9254 for spring maize, rice and winter wheat, respectively. Compared with the measured values, the simulated LAI had a linear coefficient (k) over 0.98, with R² above 0.86. The results showed that normalized LAI dynamic model provided a better description for crop population dynamics. Combined with dry matter accumulation, the average LAI, NAR (net assimilation rate), and CGR (crop growth rate) can be calculated. By means of which, the relationships between the physiological parameters and crop yield were analyzed, and the possible ways for higher crop yield were put forward accordingly.

Key words: High yield, Crop, Normalized leaf area index, Simulation model