Impact of Climate Change Adaptation Strategies on Winter Wheat and Cropping System Performance across Precipitation Gradients in the Inland Pacific Northwest, USA

Abstract

Ecological instability and low resource use efficiencies are concerns for the long-term productivity of conventional cereal monoculture systems, particularly those threatened by projected climate change. Crop intensification, diversification, reduced tillage, and variable N management are among strategies proposed to mitigate and adapt to climate shifts in the inland Pacific Northwest (iPNW). Our objectives were to assess these strategies across iPNW agroecological zones and time for their impacts on (1) winter wheat (WW) (Triticum aestivum L.) productivity, (2) crop sequence productivity, and (3) N fertilizer use efficiency. Region-wide analysis indicated that WW yields increased with increasing annual precipitation, prior to maximizing at 520 mm yr −1 and subsequently declining when annual precipitation was not adjusted for available soil water holding capacity. While fallow periods were effective at mitigating low nitrogen (N) fertilization efficiencies under low precipitation, efficiencies declined as annual precipitation exceeded 500 mm yr −1 . Variability in the response of WW yields to annual precipitation and N fertilization among locations and within sites supports precision N management implementation across the region. In years receiving <350 mm precipitation yr −1 , WW yields declined when preceded by crops rather than summer fallow. Nevertheless, WW yields were greater when preceded by pulses and oilseeds rather than wheat across a range of yield potentials, and when under conservation tillage practices at low yield potentials. Despite the yield penalty associated with eliminating fallow prior to WW, cropping system level productivity was not affected by intensification, diversification, or conservation tillage. However, increased fertilizer N inputs, lower fertilizer N use efficiencies, and more yield variance may offset and limit the economic feasibility of intensified and diversified cropping systems.

Effects of Climatic Conditions and Management Practices on Agricultural Carbon and Water Budgets in the Inland Pacific Northwest USA

“…Precipitation can have both positive and negative effects on the variability of annual carbon and water budgets, depending on whether annual rainfall is sufficient or deficient in the region . In the semiarid iPNW region, our results showed that annual NEE, GPP, EXP, NECB, and ET during the winter wheat crop years increased with precipitation for both low-and high-rainfall zones, which was also reported in other studies (e.g., Biederman et al, 2016;Maaz et al, 2017;Sakalli et al, 2017;Zhang et al, 2016). For temperature effects, annual R eco positively varied with mean annual temperature only for CAF-NT.…”

Dense subsoils limit winter wheat rooting depth and soil water depletion

“…They observed that the postharvest soil water content (105-120 cm) in an eroded ridgetop profile with shallow RRD was 28% higher than a nonrestricted profile at the same depth. Maaz et al (2017) suggested that a plateau in winter wheat yields with increasing annual precipitation in the eastern Palouse may be due to lower water-infiltration efficiency and lower subsoil water extraction. In a controlled column study, Nosalewicz and Lipiec (2014) found lower cumulative water uptake from deep layers in the column where soils were sufficiently dense to limit root-length density.…”

How Could Sustainable Agriculture Increase Climate Resilience? A Systematic Review

“…For instance, Appendix I included so many soil quality indexes different from a study to another, such as Cation Exchange Capacity (CEC), Sodium Adsorption Ratio (SAR), Albeit the difference in methodologies and indicators, the practices assessed (i.e. tillage practices, mulching techniques, and soil amendments) showed positive impacts in terms of soil quality and health improvements, which are more eminent under extreme weather conditions [87][88][89][90]. However, the reference system in comparison is to be carefully selected [91]; for instance, comparing the impacts of organic amendments on yield increase when the control is a high input system would not be in favour of the organic amendments.…”