Rice variety differences in dry matter and nitrogen accumulation as related to plant stature and maturity group¹

Contribution from the Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center. Approved for publication by the Director of the Louisiana Agricultural Experiment Station as Manuscript No. 96–09–0220.

Abstract

Differences in nitrogen (N) use by different varieties of rice (Oryza sativa L.) have been reported by numerous researchers. Some have indicated that N fertilization required for maximum yield differs between modern varieties and old varieties (varieties no longer in production); others have suggested that among modern varieties, semidwarf varieties require higher N rates than taller varieties. The objectives of this study were to evaluate differences in dry matter and N accumulation among modern long‐grain varieties in relation to plant stature (tall versus semidwarf) and maturity group (early versus very early), and to compare old varieties and modern varieties. A greenhouse pot experiment with Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) was conducted to compare old and modern long‐grain varieties at 52 days after sowing. Based on the results of the pot experiment, three varieties each from six variety groups (old varieties, modern medium‐grain varieties, and four groups of modern long‐grain varieties) were planted in the field on Crowley silt loam soil. Each variety was fertilized with three preflood N levels (0, 67, and 135 kg N ha^‐1). Plants were harvested 49 days after sowing and 25 days after 50% heading. Old and modem long‐grain varieties did not differ in total N accumulation at any N level. However, long‐grain varieties produced more grain than the old varieties at all N levels, and among long‐grain varieties, semidwarf varieties produced more grain than tall varieties when 135 kg N ha^‐1 were applied. Early and very early varieties did not differ in total N accumulation or grain yield. Varieties that produced a higher grain yield did so by partitioning more N to grain than straw. Modern medium‐grain varieties accumulated more N than old and long‐grain varieties and produced more grain with both 67 and 135 kg N ha^‐1. Medium‐grain varieties had a higher harvest index and physiological efficiency than old varieties but did not differ from long‐grain varieties. This suggests that medium‐grain varieties also partition more of their N into grain than straw and possibly are able to absorb more N from soil than old or long‐grain varieties.

Notes

Contribution from the Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center. Approved for publication by the Director of the Louisiana Agricultural Experiment Station as Manuscript No. 96–09–0220.