Increased spike density and enhanced vegetative growth as primary contributors to improvement of dryland wheat yield via surface mulching

Abstract

Context or Problem

Plastic film mulching and straw mulching are the primary cropping practices for increasing wheat yield and water use efficiency in water-deficient regions. Nevertheless, there remains a deficit in comprehensive and clear understanding of how mulching-induced alterations in yield components contribute to increased grain yield of wheat.

Objective

This study aimed to dissect the causal mechanisms connecting yield increase of wheat with alterations in yield components under mulching.

Methods

From 2012–2020, a total of 56 field experiments of winter wheat with different sites and tested cultivars were conducted in the semiarid rainfed region of Northwest China, using three treatments for each experiment: (1) straw strip mulch (SM), a partial ground mulching; (2) whole-ground plastic film mulching (PM); and (3) no mulching with wheat sown in rows, as a control (CK).

Results

Meta-analysis revealed that PM enhanced grain yield and its components to a greater extent than SM. Compared with CK, on average across the 56 experiments, SM and PM increased (p < 0.05) grain yield by 13.4 and 21.2 %, spike density (spikes ha⁻¹) by 7.0 and 12.9 %, thousand-grain weight by 1.8 (p > 0.05) and 5.5 %, total grains ha⁻¹ by 10.3 and 16.7 %, straw yield by 15.1 and 29.9 %, biomass by 14.6 and 26.2 %, net income by 774 and 68 ¥ ha⁻¹, respectively. However, Grains per spike and harvest indices did not differ among treatments (p > 0.05). The translocation contribution, translocation amount, translocation efficiency of pre-anthesis assimilate from whole plant to grains in SM and PM were 8.5 and 19.5 %, 24.2 and 72.7 %, 3.6 and 7.1 % higher than those in CK, respectively. A significant positive correlation (p < 0.01) was observed between grain yield and straw yield, as well as between each of them and spike density, the translocation contribution rate, respectively. Grain yield of SM increased with an increase in mulched area, and the grain yield in SM with 59 % of mulched area was similar to that in PM (p > 0.05).

Conclusion

The increased spike density was identified as the first component leading to higher grain yield in SM and PM over CK, while the enhanced vegetative growth (straw yield) provided photosynthetic product support for increasing spike density and transferring more pre-anthesis assimilate to grains. The economics of PM were not as attractive as those of the appropriate SM system despite the higher yield merits.

Implications

The findings potentially contribute to innovation, improvement and implementation of mulching practices for wheat cultivation in water-deficient regions.