Identifying optimal planting dates and empirical validation
To maximize crop productivity by harnessing phenotypic plasticity, we
propose a strategic approach for selecting the most advantageous
planting dates. Indeed, the timing of planting influences the weather
conditions experienced by the crop during crucial growth stages. To
identify the optimal planting dates at the three tested sites in this
study (Fig. 3a), we predicted SOC for several new planting dates with
the regression model of SOC on the identified environmental indices
(DTR183–192, PR166–195 and
UVB144–186), conditioned on the assumption of a linear
reaction norm pattern across the environments (see Methods). To ensure a
practical planting guide, we limited the dates to within 10 days before
or after the actual planting dates. We then compared the measured SOC at
actual planting dates to the predicted SOC values for early or late
plantings. We determined that planting 10 days earlier would have
resulted in higher SOC, while planting 10 days later would have
decreased SOC (Fig. 3b; Supplementary Table S8). Specifically, early
planting resulted in an increase of up to 13.80% (HF2018), whereas late
planting caused a decrease of up to 8.92% in SOC (WH2018).
To assess the general applicability of our approach for selecting
optimal planting dates, we predicted SOC at four additional sites not
included in the initial testing. We chose these sites from major oilseed
producing areas in China (Fig. 3a; Supplementary Table S9). Using
historical weather data from 2011 to 2020, we calculated the predicted
SOC for each planting date between September 10th and October 28th at
all seven sites (Fig. 3c). Early planting also generally leads to higher
SOC compared to late planting, even for the four sites from which we
lacked experimental data. The SOC varies among the seven planting sites
at the optimal and earliest planting dates, with the highest SOC
observed at CS (48.9%) and the lowest at CD (38.65%). In addition, the
decrease in SOC is more pronounced at high altitude sites (e.g., ZZ)
compared to low altitude sites (e.g., CS) when planting is not conducted
at or near the optimal date (Supplementary Table S10).
We conducted empirical validation of the above SOC predictions with
three planting dates in two new environments. We chose 50 lines from the
diversity panel and planted them in Wuhan (WH2023) and Ezhou (EZ2023) on
three different dates separated by 10 days each time. Generally, we
observed that late planting results in lower SOC in both environments.
We also predicted the SOC performance of all 50 inbred lines during the
2023 season using environmental data from the three identified indices
(DTR183–192, PR166–195 and
UVB144–186). We obtained high prediction accuracies at
both locations, with Pearson’s correlation coefficients of 0.62 and 0.67
in WH2023 and EZ2023, respectively (Fig. 4).