Soil organic carbon sequestration when converting a rainfed cropping system to irrigated corn under different tillage systems and N fertilizer rates

Abstract

The aim of this study was to evaluate the impact of 21 years of tillage and N fertilization and the conversion from a rainfed to an irrigated cropping system on soil organic C (SOC). The study was carried out in northeastern Spain in a long‐term tillage and N rate field experiment established in 1996 under barley rainfed conditions, which in 2015 was converted into irrigation with corn. Three types of tillage (conventional tillage, CT; reduced tillage, RT; no‐tillage, NT) and three mineral N fertilization rates (0, 60, and 120 kg N ha−1 under barley, and 0, 200, and 400 kg N ha−1 under corn) were compared. Annual C‐inputs as aboveground crop residues and annual SOC sequestration rate (∆SOCrate) (0–40 cm depth) were calculated in three different periods (P1, P2 and P3) under rainfed (‐R) and irrigated (‐I) conditions (P1‐R, from 1996 to 2009; P2‐R, from 2009 to 2015; P3‐I, from 2015 to 2017). At the end of P3‐I, particulate organic C (POC) was measured from the 0–5, 5–10, 10–20, 20–30, and 30–40 cm depths. Averaged over all treatments, ∆SOCrate was 492, 222, and 969 kg C ha−1 yr−1 for P1‐R, P2‐R, and P3‐I, respectively. In P1‐R and P3‐I, C‐input explained 70% of the variability of ∆SOCrate. In P1‐R, ∆SOCrate followed the order NT > RT > CT, while for N rate, order was high > medium > 0. In P3‐I at the highest N rate, ∆SOCrate followed the order NT > RT > CT. In P2‐R, ∆SOCrate did not show differences between tillage and/or N rate treatments. The increase in SOC after conversion from a rainfed to an irrigation system was mainly explained by POC, which was increased by 75% compared to the previous rainfed period. The modification of the cropping system through the introduction of irrigation and adequate crop management practices under no‐tillage and adjusted N fertilizer rates can contribute to the sequestration of large amounts of atmospheric CO2.

Impacto ambiental, social y económico de los proyectos de energías renovables eólicos y fotovoltaicos en Aragón

“…In semiarid Spanish conditions, a significant increase in SOC levels was observed three years after the conversion from rainfed to irrigated cropland (Pareja-Sánchez et al, 2020). In this last study, an increase in C inputs under sprinkler irrigated conditions explained more than 70 % of the variability in SOC change rates between rainfed and irrigated periods (Pareja-Sánchez et al, 2020). Similarly, in Central Great Plains (USA) greater SOC levels were observed in irrigated agroecosystems when different rainfed and irrigated fields were compared (Denef et al, 2008).…”

“…However, when comparing the POM-C, this proportion reached almost 38 %. In an experiment located under similar Mediterranean conditions, the POM-C fraction was identified as an early indicator of SOC changes when a rainfed cropping system was converted to irrigated maize (Pareja-Sánchez et al, 2020). In particular, these same authors observed increases of about 75 % in POM-C levels when rainfed systems were converted to irrigated maize systems (Pareja-Sánchez et al, 2020).…”

“…In dryland systems, irrigation is an excellent strategy to increase SOC levels through its positive effect on crop production and, consequently, crop residues returned to the soil (Trost et al, 2013). In semiarid Spanish conditions, a significant increase in SOC levels was observed three years after the conversion from rainfed to irrigated cropland (Pareja-Sánchez et al, 2020). In this last study, an increase in C inputs under sprinkler irrigated conditions explained more than 70 % of the variability in SOC change rates between rainfed and irrigated periods (Pareja-Sánchez et al, 2020).…”

A soil vulnerability and quality approach for a functional evaluation of agricultural land use of the territory in Navarre

“…In this framework, irrigated agriculture, both due to its fundamental role in the food and raw material supply chain globally (23% of cultivated land representing 45% of total food production), as well as for its potential as a climate-smart soil management strategy, has received worldwide scientific interest in recent decades (Velasco-Muñoz et al, 2019). The potential of irrigated agriculture to sequester C in the soil is widely documented in the literature (Lal, 2020c;Pareja-Sánchez et al, 2020). Disparity in results is however observed, with some showing positive effects and others negative or nil Mudge et al, 2017;, where differences in climate and soil characteristics seem to play a key role .…”

“…Assessing the impact of the adoption of irrigation on soil quality and functioning, and in particular on organic matter storage, seems necessary to better understand its benefits and drawbacks in terms of agricultural sustainability and climate policies. In terms of soil organic C (SOC) storage, irrigation may have positive effects in arid and semiarid areas Pareja-Sánchez et al, 2020). It is, for instance, one of the measures considered within those proposed in the "4 per 1000" initiative framework (Minasny et al, 2017), which aims to address the global challenge of securing food for a growing population, while ensuring climate change adaptation and mitigation .…”