If a 1.16 mm increase in SOM-derived AWC is multiplied by rain events during crop maturation, signifying the number of times AWC is “used,” and including 10–20 cm soil, the augmentation of AWC by SOM is larger, but an effect on crop performance is likely context-dependent. This is a limited contribution to crop transpiration, which can exceed 450 mm ( Kimball et al., 2019, maize). A recent synthesis, however, concluded that management-induced increases in SOM (10 g C/kg soil) effected on average only 1.16 mm additional AWC in the top 10 cm of soil ( Minasny and McBratney, 2018). A large effect of SOM on available water capacity (AWC) was established without consideration of limits of management-induced SOM ( Hudson, 1994). Historically, improved crop yield from SOM has primarily been attributed to SOM’s role in resource supply, either of water or nitrogen ( Gregorich et al., 1994 Arshad and Martin, 2002 Lal, 2020). Progress on these fronts relies on a sound understanding of mechanisms through which SOM benefits crops in the first place. Another, potential benefit of SOM is increasing crop yield ( Pan et al., 2009 Oldfield et al., 2018), however, we have limited ability to explain inconsistent effects of management-induced increases in SOM on crops ( Xin et al., 2016 Bradford et al., 2019 Wade et al., 2020) or to constrain potential crop benefits from SOM in future climates, as crop stressors shift ( IPCC, 2019). Multiple features of agricultural systems limit the extent by which management can alter SOM levels, but managing for even a modicum of increased SOM offers societal benefits, including climate change mitigation from the storage of carbon (C Paustian et al., 2016 Minasny et al., 2017), a component of SOM, and reduced erosion ( Barthès and Roose, 2002). By exploring the proposition that SOM catalyzes resource uptake by permitting root development, future research may constrain crop yield improvements expected from SOM management.ĭespite comprising a small proportion of the mass of agricultural soils, soil organic matter (SOM) is associated with improved soil structure ( Feller and Beare, 1997 Six et al., 2000 Dexter et al., 2008 King et al., 2019). In this framework, crop response to SOM depends on interactions of crop susceptibility to inadequate aeration or compaction, soil moisture, and “baseline” soil aeration and compaction status. Both waterlogging and compaction necessitate additional belowground investment per unit resource uptake. SOM reduces MI in dry soils and is associated with root channels to subsoil, granting crops access to deep soil water. Compaction as a restriction to root development manifests in drying soils, when mechanical impedance (MI) inflates photosynthate required to extend root tips, leading to short, thick, and shallow roots. Management practices that promote SOM reduce waterlogging by accelerating water infiltration and may promote aeration in non-saturated soils. Waterlogging, even if transient, can permanently downregulate root biosynthesis and call for expensive growth of new roots. We highlight evidence for the ability of SOM to alleviate negative impacts of inadequate aeration (mainly waterlogging) and compaction on roots. Here, we posit that to benefit crops SOM does not need to increase the supply of a growth-limiting resource it only needs to facilitate root access to extant resource stocks. Whether management-induced increases in SOM meaningfully supplement water supply has received recent scrutiny, introducing uncertainty to the mechanisms by which SOM benefits crops. The positive effect of soil organic matter (SOM) on crop yield has historically been attributed to the ability of SOM to supply crops with nitrogen and water. School of Environmental Sciences, University of Guelph, Guelph, ON, Canada.The app allow instant search, highlighting and bookmarking.Alison E. The as soon as versions are included in the app, King James Version (KJV), New American Standard Bible (NASB), New King James Version (NKJV), New International Version (NIV), New Living Translation (NLT), World English Bible (WEB). Is a Multi Version of the Bible, It contains substitute story of the Bible.
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