ABSTRACT
Soil erosion features and ideal tillage practices are not very clear at the crop seedling stage in Chinese Mollisols. Simulated rainfall experiments were conducted at the rainfall intensities of 50 and 100 mm h-1 to investigate the differences in soil erosion of a 5° hillslope during the maize seedling stage between conservation and conventional tillage measures, including cornstalk mulching (Cm), horizontal ridging (Hr), horizontal ridging + mulching (Hr+Cm), vertical ridging + mulching (Vr+Cm), flat-tillage (CK), and vertical ridging (Vr). The results demonstrated that crops could remit soil erosion at the seedling stage by reducing the kinetic energy and changing the distribution of raindrops. The conservation tillage measures significantly alleviated total runoff (11.7%–100%) and sediment yield (71.1%–100%), postponed runoff-yielding time (85 s–26.1 min), decreased runoff velocity (71.5%–96.7%), and reduced runoff and soil loss rate, compared to the conventional tillage measures. Practices with mulching showed better performance than Hr. Mulching reduced sediment concentration by decreasing runoff velocity and soil particle filtration in a manner similar to buffer strips. The contour ridge ruptured earlier at 100 mm h-1 than at 50 mm h-1 and changed the characteristics of the soil erosion by providing a larger sediment source to the surface flow. Runoff strength, rather than soil erodibility, was the key factor affecting soil erosion. Decreasing runoff velocity was more important than controlling runoff amount. The Hr + Cm treatment exhibited the lowest soil erosion and is, thus, recommended at the corn seedling stage.
KEYWORDS
soil erosion, conservation tillage, Chinese Mollisols, maize seedling stage, rainfall simulation, rainfall intensity
Introduction
Maize (Zea mays L.) is often cultivated on slopes in the Mollisols of Northeast China (You et al., 2021) for natural fertile mollic epipedon and high productivity (Zhang et al., 2012; Zhao et al., 2015). However, sloping farmlands, which are considered as the main site of soil erosion worldwide (Nearing et al., 1997; Ouimet et al., 2009; Römkens et al., 2002), occupy 57.7% of the arable land in this region (Chinese Ministry of Water Resources et al., 2010). Unfortunately, soil erosion is a natural process, but it has been vastly and needlessly accelerated by unsustainable agriculture practices globally, incurring an annual cost of $8 billion to global GDP and reducing global agri-food production by 33.7 million tons and water by 48 billion m3 (Sartori et al., 2019). With the removal of fertile surface by intensive tillage, soil erosion directly induces soil layer thinning, quality degradation, and crop yield decline (DeLonge & Stillerman, 2020; Liu et al., 2013; Montgomery, 2007, 2017; Thaler et al., 2021; Yang et al., 2016).
Conservation tillage is a widely used key agronomic measure to rebuild healthy soil worldwide (Bombino et al., 2019; Busari et al., 2015; Derpsch et al., 2014; Kader et al., 2017; Lal, 2018). It has long been considered a feasible and effective approach to control soil erosion (Bombino et al., 2021; Liu et al., 2011; Palm et al., 2014; Prosdocimi et al., 2016b; Tran & Kurkalova, 2019) and to restrict agricultural non-point source pollution (Bailey et al., 2013). Compared with conventional tillage, it has positive effects on soil physical characteristics (Blanco-Moure et al., 2012; Kumar et al., 2012; Sharratt et al., 2012), soil fertility (Polyakov & Lal, 2008; Van den Putte et al., 2012), and agricultural productivity (Hansen et al., 2012; Hobbs et al., 2008).
Previous studies have clearly demonstrated the significantly positive effects of vegetation on soil erosion (Huang et al., 2014; Keesstra, 2007; Keesstra et al., 2016). However, currently, few studies have considered the active influences of crops on soil erosion, especially at the seedling stage (Cerdà et al., 2017; Keesstra et al., 2016; Prosdocimi et al., 2016b; Wang et al., 2018). Though some reports provided better understanding and essential evidence of the effect of conservation tillage on effectively controlling soil erosion by simulated rainfall in the region, they focused on bare slope lands (An et al., 2012; Li et al., 2016; Liu et al., 2011; Lu et al., 2016; Song & Zhang, 2011; Xu et al., 2018). The status of soil erosion at the crop seedling stage under different tillage practices have been rarely reported (Ma et al., 2013). Several reasons explain the vulnerability of a slope farmland to soil erosion at the crop seedling stage: (i) a seedling crop has extremely low land-coverage rate and limited soil-solid capability because of its small canopy and root system (Figure 1), different from natural vegetation cover types (Wang et al., 2018; Zhang et al., 2009); (ii) rainfall erosivity would be further enhanced in the mid-21st century (Zhang et al., 2010); and (iii) concentrated precipitation during the crop seedling stage betided frequently in the region (Sun et al., 2000). Hence, alleviating soil erosion in the region, especially during the crop seedling stage, is important for soil loss reduction, aquatic environment improvement, and agricultural sustainable development.
In line with the above-mentioned findings, our study evaluated the effects of four conservation and two conventional tillage practices on soil erosion under simulated rainfall conditions at the maize seedling stage on a black soil sloping farmland in Northeast China. Our study provides insights to determine suitable tillage measures to control soil erosion at the corn seedling stage in the studied region and a reference for further studies on alleviating erosion pressure in other regions.