Tillage and nitrogen fertilization enhanced belowground carbon allocation and plant nitrogen uptake in a semi-arid canola crop–soil system

Abstract

Carbon (C) and nitrogen (N) allocation and assimilation are coupled processes, likely influencing C accumulation, N use efficiency and plant productivity in agro-ecosystems. However, dynamics and responses of these processes to management practices in semi-arid agro-ecosystems are poorly understood. A field-based 13CO2 and urea-15N pulse labelling experiment was conducted to track how C and N allocation and assimilation during canola growth from flowering to maturity were affected by short-term (2-year) tillage (T) and no-till (NT) with or without 100 kg urea-N ha−1 (T-0, T-100, NT-0, NT-100) on a Luvisol in an Australian semi-arid region. The T-100 caused greater (P < 0.05) belowground C allocation and higher (P < 0.05) translocation of soil N to shoots and seeds, compared to other treatments. Microbial N uptake was rapid and greatest in the fertilized (cf. non-fertilized) treatments, followed by a rapid release of microbial immobilized N, thus increasing N availability for plant uptake. In contrast, management practices had insignificant impact on soil C and N stocks, aggregate stability, microbial biomass, and 13C retention in aggregate-size fractions. In conclusion, tillage and N fertilization increased belowground C allocation and crop N uptake and yield, possibly via enhancing root–microbial interactions, with minimal impact on soil properties.

Pollinators enhance crop yield and shorten the growing season by modulating plant functional characteristics: A comparison of 23 canola varieties

“…According to a well-documented trade-off between below- and above-ground resource acquisition also known as “optimal partitioning”, “balanced growth” or “functional equilibrium“ 74–76 , plants preferentially allocate biomass to the organs with the highest demand for resources, and shift this allocation in response to changing conditions 77,78 . In support of the idea, tillage and nitrogen fertilization increased carbon allocation to the roots of a canola crop in a semi-arid dryland 79 . Similarly, although insect pollination, on average, decreased canola root size in our experiment, canola plants with adequate root investment to support rapid resource acquisition and use, eventually produced high-quality seeds by avoiding the potential costs of investment in late maturing seeds.…”

Benefits and tradeoffs of reduced tillage and manure application methods in a Zea mays silage system

“…Best management practices affect nutrient retention and GHG emissions by altering their drivers. Nitrogen losses can be reduced by incorporating added N into soils to minimize gaseous and runoff losses (Daverede et al., 2004; Duncan et al., 2017; Kulesza, Maguire, Thomason, Hodges, & Pote, 2014) and maximize plant and microbial uptake, which are enhanced when water, temperature, and substrate (for microbes) are not limiting (Hart, Stark, Davidson, & Firestone, 1994; Sarker et al., 2017). Soil CO 2 flux, a combination of microbial and root respiration (Oertel, Matschullat, Zurba, Zimmermann, & Erasmi, 2016), increases with temperature (Lloyd & Taylor, 1994) and C availability (Hungate, Chapin, Zhong, Holland, & Field, 1997) as long as water is not limiting.…”

Deep ploughing in the summer fallow season and optimizing nitrogen rate can increase yield, water, and nitrogen efficiencies of rain-fed winter wheat in the Loess Plateau region of China

“…Increased yields may also be because of more efficient use of soil water and available nitrogen due to tillage practices. Tillage during the summer fallow season increases pre-anthesis N translocation and yield ( Sarker et al, 2017 ; Liang et al, 2019 ). The improvement in plant N under tillage was largely caused by an increase in the N available in the soil ( Soon et al, 2007 ; Soon, Brandt & Malhi, 2006 ; Ruisi et al, 2016 ).…”