Comparisons of Methods to Compute Peanut Seed Size Distribution by Crop Growth Models

Abstract

The value of a peanut crop is determined by yield and grade. The grade of peanuts is largely dependent on seed size distribution. Higher percentages of large seeds result in a higher grade and subsequently a higher profit for the grower. Peanut growth models currently predict yield and seed mass distribution, however, they do not predict seed size distribution which is critical for determining overall crop value. The objective of this work was to develop and evaluate a procedure to compute seed size distribution based upon the seed mass distribution predicted by a crop growth model. A linear relationship between individual seed mass and seed size was derived from field data and used to compute seed size distribution from predicted seed mass distribution. Mass of sound mature kernels (SMK) and extra large kernels (ELK) was predicted for 15 field experiments and compared to measured results. Three hypotheses were tested to improve the computed seed size distribution in the CROPGRO-Peanut crop growth model. Hypotheses relating to variable seed and shell growth rate reduced errors between predicted and observed mass of SMK and ELK. However, adjusting the average final weight per seed coefficient required by the crop growth model resulted in the best predictions of seed size distribution. The results of this work can provide a dynamic method of predicting mass of SMK and ELK required to determine crop grade, value, and harvest date when coupled with a dynamic crop growth model.