Allometric relationship and yield formation in response to planting density under ridge-furrow plastic mulching in rainfed wheat

Abstract Allometric relationships in plants have received a wide interest, but it is little used to interpret yield formation and the relationship between individual fitness and population yield (i.e. grain yield per unit area) in crops. For this purpose, we conducted a density-dependent yield-formation experiment in field-grown wheat with flat-planting (CK) and ridge-furrow with plastic-film mulch (RFM). The results indicated that increased population densities (i.e. seed rates of 60, 140, 220, 300, 380 and 460 kg ha−1) decreased the reproductive allocation at the individual level under both farming systems, but the maximum wheat yield was observed at medium densities (300−380 kg ha−1). While there exists a selective conflict between individual survival and population yield, our experiments in dryland wheat showed that a moderate reproductive allocation at the level of the individual achieved better yield performance at the population level. However, the principal component analyses (PCA) showed that optimal individual and population performances were achieved synchronously at 220 kg ha−1 under RFM treatment. We employed the law of constant final yield (CFY) to interpret the biomass-density relationships in the two farming systems. While the population grain yield started to decline from the peak values at medium density, total biomass continued to increase with density and then leveled off at 300, 380 and 460 kg ha−1. Critically, the decrease in yield occurred at higher plant densities in the RFM system. Allometric relationships further showed that the RFM treatment led to significantly higher reproductive allocation than the CK treatment at the individual plant level. This is the first report supporting that the theory that reproductive allometry can be applied to interpret the tradeoff between population productivity and individual performance, and the mechanisms of yield-improvement of the RFM system.