Elsevier

Applied Soil Ecology

Volume 168, December 2021, 104122
Applied Soil Ecology

A short-term study of soil microbial activities and soybean productivity under tillage systems with low soil organic matter

https://doi.org/10.1016/j.apsoil.2021.104122Get rights and content

Highlights

  • Dehydrogenase activity of soil and root nodulation was reduced by no-tillage.

  • No-tillage system decreased nitrogen uptake, soybean growth and productivity.

  • Minimum tillage improved soil microbial activities and soybean nodulation.

  • The highest nitrogen uptake was observed under minimum tillage.

  • Minimum tillage had a positive impact on soybean productivity in a short-term.

Abstract

Since tillage has an important role in changing soil properties and crop performance, a field experiment was conducted during two growing seasons (2018 and 2019) to assess the possible effects of three prevalent tillage systems (no-tillage, minimum and conventional tillage) on soil microbial activity, nodulation and yield of three soybean (Glycine max) cultivars (Williams 82, Zan and M7) under low content of soil organic matter (~1%). As a result, minimum and no-tillage improved soil basal respiration, metabolic quotient, acid phosphatase and β-glucosidase activities, while decreased soil pH, temperature and NO3-N concentration compared to conventional tillage. Under no-tillage, soil dehydrogenase activity, nodule formation, nitrogen uptake, growth, SPAD values and productivity of soybean cultivars were decreased, and also seedling establishment and day to maturity were delayed in comparison with conventional tillage. Nevertheless, soil microbial biomass carbon and organic matter content were not altered under no-tillage. In contrast, compared to other tillage practices, soil microbial biomass carbon, dehydrogenase activity and nodule formation were increased by minimum tillage resulted in an enhance in nitrogen uptake (~15%), growth, SPAD values, ground cover, grain, protein and oil yields of soybean (~6%). Averaged across tillage and year, the higher nodulation and nitrogen uptake were belonged to M7 and Zan cultivars, which resulted in more grain and protein yields. However, the highest oil yield was recorded in Williams 82. Overall, minimum tillage did not increase the soil organic matter content, but that improved soybean productivity by enhancing soil microbial activities, nodulation and nitrogen uptake; thus, it could be a suitable agronomical practice in the short-term to achieve acceptable yield.

Introduction

Soil organic matter is a critical parameter in adjusting biological activities, and its adequate amount is necessary for successful sustainable agriculture (Belmonte et al., 2018; Torabian et al., 2019). In contrast, the low organic matter of soil might reduce microbial activities in rhizosphere (Tiessen et al., 1994). The formation of soil organic matter is almost a degradation process requiring considerable time. It is suggested that some practical ways such as using cover crops, suitable crop rotation and tillage systems, and application of organic fertilizers instead of chemicals to enhance soil organic matter (Magdoff and Weil, 2004).

Soil tillage is a mechanical action that modifies soil climate for cultivation of crops, which can provide a suitable condition for seed germination, seedling establishment and root growth (Lampurlanes et al., 2016). There are various tillage systems such as conventional, conservation tillage and no-tillage that have specific positive and negative impacts on rhizosphere and ecosystems (Li et al., 2018). Conventional tillage is the most common tillage system leaving less than 15% of crop residues on the soil surface before sowing the next crop. Results of various experiments revealed that conventional tillage causes some soil-related problems such as decreasing soil organic matter, deteriorated water percolation, and increasing soil erosion compared to conservative practices (El Titi, 2002; Weber et al., 2017). However, conservation tillage leaves 30% or more crop residue to cover the soil surface before planting. It is generally designed to reduce soil erosion and preserve organic matter and microbial activities depending on depth and number of plows, cover crops and residues remain on the soil surface (Bausenwein et al., 2008; Ehlers and Claupein, 2017; Hati et al., 2020). Under No-tillage system, soil is usually left undisturbed from harvest of the previous crop up to sowing the new crop (Leon et al., 2017).

On the other hand, tillage practices can alter nodulation process (Anikwe et al., 2016) and nitrogen (N) metabolism in legume plants such as soybean (Glycine max) (Torabian et al., 2019; Virk et al., 2020). Many researches indicated that conservative tillage systems can improve nodulation process by preserving organic matter (El Titi, 2002; de Pontes et al., 2017). For instance, Heidari et al. (2016) showed that conservation tillage in a sandy loam soil texture noticeably enhanced microbial biomass and soil organic carbon in soybean farms. A similar result for soybean has been reported by Aulakh et al. (2017). Microbial activities play an important role in preserving soil organic matter and nutrients bioavailability in an optimum level for agronomical practices (Rashid et al., 2016). The organic matter of soil is the main factor in adjusting interactions of soil biota with plants (Khan et al., 2016). Torabian et al. (2019) reported that conservation and no-tillage systems can modify soil organic matter content and microbial activities of soil. Hughes and Herridge (1989) stated that reduced soil NO3-N under no-tillage increases soybean nodulation and microbial activities of soil. Wang et al. (2020) claimed that soil microbial community structure and activity can be affected by tillage systems. In this regard, Mathew et al. (2012) reported that soil microbial activities were higher in no-tillage soil compared to conventional tillage. Kandeler et al. (1999) stated that the activity of different enzymes such as phosphatase was enhanced under conservation tillage system.

Accordingly, soybean growth and productivity could be influenced by tillage practices (de Pontes et al., 2017). Li et al. (2017) indicated an enhance in root length and density of soybean under no-tillage system under a long-term experiment. Okoth et al. (2014) reported that no-tillage increased biological N fixation and shoot biomass of different soybean cultivars under various kinds of soil texture (sandy clay loam, sandy clay and loamy sand) but did not improve grain yield. Zotarelli et al. (2012) found that organic carbon pools, biological N fixation and grain yields of soybean were improved under no-tillage system with clay soil texture. In most cases, the impacts of conservation and no-tillage on soybean growth and productivity have been positive. However, there are some reports showing negative or insignificant effects of conservation tillage system on symbiotic activities and grain yield. Nouri et al. (2018) reported that there was no noticeable difference in grain yield of soybean under two minimum and conventional tillage systems.

Due to the various responses of soil microbial activities and crop performance to tillage systems, this research was designed and conducted in order to evaluate the possible short-term impacts of three prevalent tillage systems (conventional, minimum and no-tillage systems) on soil microbial activities and soybean productivity under low organic matter of soil.

Section snippets

Experimentation

The field experiment took place over a two-year period (2018 and 2019) in Tabriz, East Azerbaijan province, Iran (37°58′22.1″N and 46°02′31.6″E, 1280 m above sea level). The climate is subtropical according to Koeppen's classification with average 360 mm annual rainfall. Major soil (Inceptisol soil) characteristics and weather conditions of experimental site are presented in Table 1. The experiment was designed as randomized complete block with a split plot arrangement and four blocks including

Soil properties

Averaged across cultivars and years, soil temperature, pH and NO3-N concentration were affected by tillage systems (Table 2). The lowest values of soil temperature, pH and NO3-N concentration were observed under no-tillage condition. In contrast, the highest values of these parameters were recorded under conventional tillage. Reductions of soil NO3-N concentration under no-tillage and minimum tillage were 35% and 27%, respectively, compared to conventional tillage. Minimum and no-tillage

Discussion

The results of a short-term study (two years) about the impacts of different tillage systems on various parameters of soil physicochemical attributes and soybean productivity in a well irrigated plot with low organic soil revealed that soil organic matter could not be affected by tillage practice. This proves that stabilization of organic matter requires a long time. Bessam and Mrabet (2003) reported that after 4 years of no-tillage an extra 5.62 t ha−1 of soil organic carbon was sequestered in

Conclusion

Our results revealed that tillage methods can modify soybean nodulation and productivity under low content of soil organic matter content. No-tillage system improved some of the microbial activities of soil such as acid phosphatase and β-glucosidase, while reduced dehydrogenase activity, nodulation, N uptake, and crop productivity. In contrast, nodulation, N uptake, and soil microbial biomass and activities, especially dehydrogenase activity were improved by minimum tillage. The effects of

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

We appreciate the University of Tabriz and Agriculture Research, Education and Extension Organization of Iran for helping us to conduct the research.

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