Variation in dry matter and nitrogen accumulation and remobilization in barley as affected by fertilization, cultivar, and source–sink relations

Abstract

Barley ( Hordeum vulgare L.) is one of the most important cereals worldwide and is being increasingly grown in many areas of the world, but there is a lack of information about the physiological processes limiting grain yield. A two-year field study was conducted with the objective of determining the effect of different rates of nitrogen (N) (control, 60 kg N ha −1, and 120 kg N ha −1) on source–sink relations, dry matter and N remobilization, and grain yield. Therefore, the source–sink ratio was manipulated to examine the factor(s) limiting grain filling under rainfed conditions. The treatments were: I, control; II, half of the spike was removed; III, the entire spike was removed. The distribution of dry matter, N among grains, and culms and leaves were analyzed at anthesis and harvest. Dry matter accumulation and partitioning into different plant parts were affected by the fertilization treatments and increased as the N level increased. At anthesis, the amount of leaf + culm dry matter was greater than the amount of spike dry matter. N fertilization slightly affected the N concentration of the different plant parts at anthesis and at maturity. N content was affected by the fertilization treatments and was increased by 62% over the two years of the study compared with the control. In addition, dry matter remobilization was an average of 40% higher in the fertilized treatments compared with the control, which indicates that fertilization led plants to translocate higher amounts of dry matter. N remobilization was affected by the fertilization treatment and by the sink reduction. The spike reduction treatment increased the pre-anthesis assimilates and contribution to grain, indicating that the dry matter remobilization from vegetative tissues were very important for grain development. In contrast, N translocation efficiency was similar under sink reduction. Grain yield was determined by biomass and harvest index, and at the half spikes, there was a higher contribution at the harvest index. In addition, grain N yield was determined more by grain yield and less by the N concentration. The present study indicates that N fertilization and sink size can affect dry matter and N accumulation, partitioning, and remobilization in barley, which can affect grain yield.