Exploring N fertilizer reduction and organic material addition practices: An examination of their alleviating effect on the nematode food web in cropland

Abstract

Excessive nitrogen (N) fertilization in croplands results in environmental problems, such as soil quality deterioration, water contamination, and biodiversity losses, which threaten the sustainable development of soil ecosystems. The soil nematode food web plays key roles in soil organic matter decomposition and nutrient cycling, and thus the sustainable development of cropland ecosystems. However, how the negative impact from the excessive N fertilization on the nematode food web is effectively alleviated remains uncertain. This study aimed to explore the effects of different N fertilization management practices (N fertilizer reduction or organic material addition) on alleviating the negative effects on the nematode food web in croplands. Four treatments/ management practices were examined: conventional fertilization (N control), N fertilizer reduction of 100% (N 0), N fertilizer reduction of 50% (N 1), and conventional fertilization with organic material addition (N +S). The results showed that the abundance of nematodes and microbial phospholipid fatty acids (PLFAs) both increased in the treatments of N 0 , N 1 , and N +S compared with N. Besides, N +S also increased the nematodes' biomass, diversity, and metabolic footprint, which correspondingly strengthened the nutrient turnover through the nematode food web. Overall, two management practices 1)N fertilizer reduction and 2) organic material addition, differ in the abiotic or biotic process in alleviating the negative effects of N fertilization on the nematode food web. The reducing N fertilization can directly alleviate the negative effect of fertilizer on soil acidification and then benefit for the growth of microorganisms and nematodes. The exogenous carbon input from organic material addition might promote carbon flowing and immobilization into nematode food web, and ultimately enhance the stability of soil food web.

Effect of Reduced Nitrogen Fertilization on the Chemical and Biological Traits of Soils under Maize Crops

“…Qiao et al [45] reported that N additions in tea plantations acidified soils (a significant decrease by 0.41 pH unit on average) and produced soil nutrient imbalance [45]. Kou et al [46] concluded that N fertilizer reduction directly decreased the amount of NO 3 -N in the soil and then alleviated the soil acidification caused by the excessive use of N fertilizers. In contrast, no significant difference in TN was observed upon a 25% reduction in chemical N fertilizers in the study conducted by Liu et al [47].…”

Effect of Reduced Nitrogen Fertilization Recommended by the EC "From Field to Table" Strategy on the Chemical and Biological Traits of Soils under Maize Crops

“…Qiao et al [40] reported that N additions in tea plantations acidified soils (a significant decrease by 0.41 pH unit on average) and produced soil nutrient imbalance [40]. Kou et al [41] concluded that N fertilizer reduction directly decreased the amount of NO3-N in the soil and then alleviated the soil acidification caused by excessive use of N fertilizers. In contrast, no significant difference in TN was observed upon 25% reduction of chemical nitrogen fertilizers in the study conducted by Liu et al [42].…”

Increasing Levels of Physical Disturbance Affect Soil Nematode Community Composition in a Previously Undisturbed Ecosystem

“…FMF with a larger area in the control treatment during May 2018 indicated a higher metabolic activity and inflow of C, which was used for nematode production ( Ferris, 2010 ). The high availability of organic matter in the control treatment increased the abundance of predators and omnivores and activated a stronger pathway through the predator channel, which may promote the stronger metabolic process and stability of the soil food web ( Ferris, 2010 ; Thakur and Geisen, 2019 ; Kou et al ., 2020 ). On the other hand, the FMF area was smaller in tillage treatments, indicating that smaller quantities of C were used for nematode production and lower metabolic activity due to the low availability of resources and lower predator-omnivore numbers ( Ferris, 2010 ).…”