Can ridge-furrow with film and straw mulching improve wheat-maize system productivity and maintain soil fertility on the Loess Plateau of China?

Highlights

• Four ridge-furrow planting patterns were adopted in crop rotation.

• RWS and RBS achieved higher soil moisture, yield, WUE, and suitable soil temperature.

• After three years, RWS and RBS remained significantly higher soil fertility.

Abstract

Ridge-furrow mulching patterns are beneficial to improve crop yields and rainwater use efficiency, but it is not clear whether they can improve productivity and simultaneously maintain soil fertility on the Loess Plateau of China. A three-year (2013–2016) field trial was conducted during the rotation of wheat (Triticum aestivum L.) – maize (Zea mays L.) to investigate the effects of ridge-furrow mulching patterns on soil moisture, soil fertility, grain yield, and water use efficiency (WUE). Four ridge-furrow planting patterns included: (1) white plastic film mulch over the ridge (RW), (2) straw mulch over the furrow (RS), (3) white plastic film mulch over the ridge and straw mulch over the furrow (RWS), and (4) black plastic film mulch over the ridge and straw mulch over the furrow (RBS). Flat planting without mulch was CK. The results showed that RW, RS, RWS, and RBS significantly improved soil water storage and aboveground biomass throughout each winter wheat and summer maize growing season compared with CK. Finally, winter wheat grain yield and WUE in the four mulching treatments markedly increased by 13.0–32.9% and 22.5–41.5% in a wet and cool season, 15.5–35.2% and 19.3–41.9% in a season with normal rainfall and temperatures, and 27.2–58.9% and 15.3–33.4% in a dry and warm season, respectively. Maize grain yield and WUE increased by 12.8–35.0% and 19.5–46.2% in a season with normal rainfall and temperature, 15.0–38.5% and 18.0–39.9% in a dry and cool season, and 17.4–50.5% and 13.0–42.5% in a dry and warm season, respectively. Among the four mulching treatments, RWS and RBS significantly improved the yield and WUE of wheat and maize relative to RW and RS over the three years. After three years, soil total nitrogen content in RWS and RBS was significantly greater than in RS. Besides, soil microbial biomass carbon and nitrogen, and soil dissolved organic carbon and nitrogen contents in RWS and RBS were all markedly higher than in RW and RS. Our results indicated that RWS and RBS were a promising agricultural practice that improved crop production and simultaneously maintained soil fertility in a rain-fed semi-arid region of China.

Introduction

The global population will reach nine billion by 2050, which implies that there will be a substantial increase in food production demand (Tilman et al., 2011). Therefore, farmers will have to produce greater crop yields from a limited and decreasing area of arable land (Fang, 2018). Water is one of the major limiting factors on crop yield and will become scarcer and more unevenly distributed across the world due to global climate change and the influence of human activity in the 21st century (Karthe et al., 2014). Therefore, to ensure food security, regions with different climate characteristics and different amounts and distributions of water resources need to find adaptive water-saving and yield-increasing agricultural practices.

The Loess Plateau, which is spread over approximately 64 million hectares, supports about 100 million people and is the major dryland farming area of China (Chen et al., 2015). Groundwater resources are sparse and deep, which means that most of the farmland on the Loess Plateau relies solely on rainfall (Li and Xiao, 1992). However, precipitation at many sites is only 200–400 mm per year and more than 60% of the rainfall falls between June and September in this region (Wang et al., 2012a, Wang et al., 2012b), and precipitation has declined at a rate of 1–2 mm per year over the last five decades (Wang, 2009). The limited and uneven distribution of water resources and high evaporation rates constrain agricultural development on the Loess Plateau. It has been reported that the two major local cereal crops, maize and wheat, have low yields (2500–3500 kg ha⁻¹ and 1500–3000 kg ha⁻¹, respectively) due to the imbalance between crop water requirements and water supply (Hu et al., 2009, Ye and Liu, 2012). The region has been exceedingly poor for a long time and farmers cannot satisfy the primary demand for grains made by the increasing population (Li, 1999). Therefore, agricultural practices that increase crop yields by reducing soil evaporation and improving rainwater use efficiency are urgently needed on the Loess Plateau.

Plastic film mulching (PM) can reduce soil evaporation, increase soil moisture and temperature, and improve crop yield and water use efficiency (WUE) (Li et al., 2013, Yaghi et al., 2013, Liu et al., 2015, Gu et al., 2019a). Therefore, it has been widely adopted on the Loess Plateau over the last few decades. Recently, ridge-furrow film mulching (RFFM), which combines PM and the ridge-furrow planting method, has become popular because it not only has the benefits of PM but also can efficiently collect and utilize rainwater compared with conventional flat planting without film mulching (Gan et al., 2013). However, the higher soil moisture and temperature under RFFM have led to a more rapid conversion of soil nutrients because RFFM improves the micro-ecological environment for microorganisms compared with flat planting without mulching (Gu et al., 2018a). For example, previous research has shown that soil organic carbon (SOC) decomposition was more rapid under RFFM, and this has led to increasing concern about the sustainability of the soil over the long-term when the RFFM method is used (Gan et al., 2013, Steinmetz et al., 2016). Therefore, it is particularly important to explore an optimal agricultural practice that, when combined with RFFM, can simultaneously improve crop productivity and maintain soil fertility on the Loess Plateau.

In recent years, straw mulching has also become widespread in winter wheat-summer maize double-cropping systems on the Loess Plateau due to the increased use of machinery and response to a ban on straw burning by the Chinese government (Dong et al., 2018). Straw mulching can reduce soil evaporation loss and keep the soil warmer in winter and cooler in summer (Chen et al., 2007). However, straw mulching has not always been shown to increase maize and wheat yields due to poor soil heat and moisture preservation effects (Taa et al., 2004, Gao et al., 2009). Nevertheless, straw mulching is seen as an effective practice that can provide soil organic matter, and greatly improve the SOC concentration (Dong et al., 2018). Therefore, we hypothesized that combining straw mulching and RFFM would concurrently improve crop productivity and maintain soil fertility in a winter wheat-summer maize double-cropping system. The overall objectives of this study were to 1) compare the effects of different film and straw mulching patterns on soil moisture, soil fertility, grain yield, and WUE in different meteorological years; and 2) determine which pattern can improve crop productivity and simultaneously maintain soil fertility in a winter wheat-summer maize double-cropping system on the Loess Plateau of China.