Responses of crop productivity and physical protection of organic carbon by macroaggregates to long‐term fertilization of an Anthrosol

Abstract

Summary Soil organic carbon (SOC) sequestration in the soil of arable land has been recommended as a ‘win–win strategy’ for improving soil quality and crop productivity, and for mitigating the effects of climate change. With data from a 35‐year field experiment, we investigated the effects of organic manure and synthetic fertilizers on the mechanisms of organic carbon (OC) protection in macroaggregates and the relations between crop productivity and OC under an intensive wheat (Triticum aestivum L.) and maize (Zea mays L.) cropping system on an Anthrosol in northern China. The study involved nine treatments consisting of different combinations of synthetic fertilizers and organic manure. Soil samples taken from the 0–10‐cm and 10–20‐cm layers after 35 years of experimentation were separated into four physical fractions within the macroaggregates and analysed for changes in OC. In comparison with the control without any addition of fertilizer, long‐term application of nitrogen and phosphorus had no effects on SOC and OC contents of the macroaggregate fractions. In contrast, the application of organic manure significantly increased SOC and OC contents of macroaggregate fractions, apart from mineral‐associated organic carbon (MOC). Soil organic carbon was strongly and positively correlated with OC content in the intra‐microaggregate particulate organic carbon fraction (iPOC), indicating that SOC sequestration occurred primarily in the form of the physically protected particulate organic carbon fraction in the Anthrosol investigated here. A quadratic‐plateau model described the relation between crop yields and SOC well, and the critical SOC content, above which there was no yield response to increasing SOC, was about 9 g kg−1, or 25 Mg ha−1. Thus, the input of available C should be adjusted once this critical SOC content has been reached to guarantee the desired level of soil productivity and efficiency of SOC sequestration. Highlights Long‐term application of dairy manure markedly increased SOC contents in plough layer. Manure application increased OC contents in macroaggregate fractions, except MOC. SOC was significantly and positively correlated with iPOC. The critical SOC content to obtain desired crop yield was ca. 9 g kg−1 in an Anthrosol.

Carbon Sequestration in Irrigated and Rain-Fed Cropping Systems Under Long-Term Fertilization Regimes

“…10.0 g kg −1 and 8.8 g kg −1 for the irrigated and rain-fed experiments, respectively. Our value is lower than the 20 g kg −1 reported for a rain-fed system in Alberta, Canada (Howard and Howard 1990) but is close to the average "threshold" SOC values (between 7.8 and 15.9 g kg −1 ) based on a large number of long-term experiments conducted across China (Zhang et al 2016;Xie et al 2018). The threshold value of SOC is also specific to the soil type.…”

The effect of 34-year continuous fertilization on the SOC physical fractions and its chemical composition in a Vertisol

“…22 reported that a combination of straw and chemical fertilization increased the content of cPOM, iPOM, and S + C fractions in an Inceptisol (in Zhengzhou) but decreased in a Mollisol (in Gongzhuling). In contrast, manure application significantly increased all SOC fractions in an Ultisol 23 , Anthrosol 24 and Inceptisol 22 . Clearly, the effect of various fertilization practices on the SOC physical fractions remains largely unknown.…”

Improving soil quality for higher grain yields in Chinese wheat and maize production

“…Many studies have demonstrated a correlation between soil quality and organic recycling (Lal, ; Oldfield et al, ). However, the crop yield response to the recycling of organic materials to fields remains unclear: Yields have reportedly increased (Akhtar et al, ; Xie et al, ), decreased (N'Dayegamiye, ), or not responded to recycling (Baldi et al, ; Hijbeek et al, ). These uncertain responses of yield have dampened local farmers' enthusiasm for recycling organic materials to their fields (Hijbeek et al, ; Oelofse et al, ).…”