Is it Sustainable to Cultivate a Monoculture of Durum Wheat with Prolonged No-Tillage Management?

Research Article

Ann Agric Crop Sci. 2022; 7(1): 1105.

Is it Sustainable to Cultivate a Monoculture of Durum Wheat with Prolonged No-Tillage Management?

Troccoli A1*, Russo M1 and Farina R2

¹Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca cerealicoltura e colture industriali, Foggia, Italy

²Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca agricoltura e ambiente, Rome, Italy

*Corresponding author: Antonio Troccoli, Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca cerealicoltura e colture industriali, Foggia, Italy

Received: December 01, 2021; Accepted: January 03, 2022; Published: January 10, 2022

Abstract

The prolonged effect of no-tillage (NT) and conventional tillage (CT) treatment on durum wheat (Triticum durum Desf.), continuously grown in Southern Italy, has been evaluated in experimental fields for sixteen years (1994/95-2009/10) to ascertain whether the yields and quality of the grain as well as some soil characteristics had changed. The average grain yield in CT (2.70 ± 0.96 t ha-1) and NT (2.63 ± 0.74 t ha-1) treatment was not significant. CT treatment showed higher values of plant height and grain weight (74.2 cm and 43.2 g) than NT (71.0 cm and 41.8 g). Regarding to the semolina quality, the values of the gluten index and the dough strength (W parameter) as well as the protein content and the yellow index were not significantly different for the NT and CT treatments. As for soil moisture, the NT treatment stored in the soil profile, and over time, about 13% more water than the CT one. In the upper soil layer of the NT treatment the SOC value (16.0 ± 2.2 g kg-1) was 13.2% higher than CT one (14.2 ± 1.2 g kg-1) while the CT treatment (13.7 ± 0.5 g kg-1) showed in the lower soil layer a SOC value of 30.2% higher than the NT one (9.6 ± 1.9 g kg-1). Hence the prolonged no-tillage adoption in conditions of continuous durum wheat cultivation, even with slight losses in yield but not in the quality of grain or semolina, would seem sustainable.

Keywords: Durum wheat monoculture; No-tillage; Sustainability; Soil moisture content; Soil organic carbon

Introduction

Long-term experiments represent a via for testing the sustainability of different farming practices, for example yields trend over decades, also when the same practices can be considered unsustainable. Experiments at Rothamsted are a classic demonstration that “grain yields can be sustained (and even increased) for almost 150 years in monocultures of wheat and barley given organic or inorganic fertilizer annually” [1].

These results show that some practices considered agronomically unsustainable, as monoculture, however can be maintained, providing the farm the ability to produce the same crop perpetually, clearly under certain circumstances.

Similarly, an agricultural system addressed to obtain constant and durable yields without depleting soil fertility can be considered an eco-sustainable integrated system since it uses less non renewable resources and promotes the reduction of costs for both the production and environment [2]. The FAO in 90’s launched the concept of “sustainable agriculture”: “productive activity that aims to the conservation of soil, water, plant and animal genetic patrimony, technically adequate, economically valid, and socially acceptable”.

Farmers generally consider the production level of the durum wheat to be an important parameter but in variable or unfavourable agro-climatic conditions they find the yield stability more interesting [3]. However, yield stability as well as the level of production of durum wheat can be strongly conditioned by several factors: agricultural practices (soil tillage, fertilization, irrigation, weed and pest control, residues management and others), soil properties (texture, OM, nutrients availability, microbial activity, pH, moisture and others), type of crop (monoculture, rotation with oilseeds, legumes or cover crop) besides to climate conditions, especially high heat and low rain during grain ripening [4-9].

Among the agricultural sustainable practices, the no-tillage represents one of the three approaches included in the conservation agriculture concept [10] that can help in maintaining crop productivity, soil fertility and environmental sustainability. Regarding the effects of no-tillage on crop yields, studies carried out on this aspect report controversial results: some show that yields in reduced or no tillage systems are like those of conventional tillage [11], unlike others where yields decreased [9]. An overview of the effects of no tillage on crop yields was provided by Pittelkow et al. [12] who performed a metaanalysis on 678 studies and 6005 observations, including 50 crops and 63 countries. They find no-till yields matched conventional tillage yields for oilseed, cotton, and legume crop categories while, among cereals, the negative impacts of no-till were smallest for wheat (-2.6%) and largest for rice (-7.5%) and maize (-7.6%). No-till performed best under rainfed conditions in dry climates, with yields often being equal to or higher than conventional tillage practices. Furthermore, yields in the first 1-2 years following no-till implementation declined for all crops except oilseeds and cotton, but matched conventional tillage yields after 3-10 years except for maize and wheat in humid climates. Finally, the overall yields in the no-till system were reduced by 12% without the addition of nitrogen fertilizer and by 4% with the addition of inorganic nitrogen.

However, it is generally recognized that no-till is an agricultural practice that leads to significant benefits of both an environmental nature (reduction of wind and water erosion; increase in soil biological activity, nutrient cycle, soil water retention capacity, infiltration of water and efficiency in the use of water) and economic (greater profitability due to the decrease in energy consumption and labor) [13-15].

As important indicators of the soil quality, an interesting debate concerns the effect of no-tillage on the carbon and nitrogen content of the soil, especially if it is true that undisturbed agricultural soils can recover higher quantities of these elements than the conventional tillage system.

The regular use of moldboard plough for seedbed preparation or disking for weed control can result in a significant decline in soil of organic matter content [16,17]. Accordingly, the loss of soil organic C may be due to disruption of soil aggregates [18], stimulation of shortterm microbial activity by enhanced aeration [19], and decomposition into the soil of mix fresh. A further loss of C organic may derive from erosive phenomena due to action of wind or water (runoff) on soil tillage [20]. Adversely, under CA system the less disturbed soil results in a significant organic C accumulation [21] with consequent reduction of gas emissions, above all CO2, to the atmosphere [17]. In particular, it has been demonstrated that the C sequestration mainly occurs in the topsoil layers with little overall effect on C storage in deeper layers [13]. In fact, in a wheat-fall rotation system after 20 years of no-tillage application has been observed an increase of 6.7 t C ha-1 in the top 20 cm respect to conventional tillage [22]. Halvorson et al. [23] reported a decreasing pattern in SOC as NT < MT < CT where the most SOC is retained under NT. Omara et al. [24] reported, under continuous monocropping practice, an average of 21% more SOC under NT than CT. In other studies, a significant SOC increase under NT was found to be 17% higher in long-term (39 years) compared to short-term NT (9 years) from the 0-15 cm soil layer, while no differences were observed between samples obtained from a 15-30 cm soil depth [25]. However, some controversies about the real capacity of no-tillage system to sequester a higher amount of soil C, especially when the whole soil profile is considered, are still unresolved [26]. In fact, insignificant gain of soil C in the whole profile can take place depending on several factors like the amount of residues returned into soil, the variation in the agricultural practices implemented and the type of climate. As already seen, a lot of information regarding the variations of SOC and N storage under NT compared to CT is reported for the topsoil layer (up to 10 cm deep), whereas more information would be needed for the deeper soil layers [27]. Mazzoncini et al. [28] found that, under Mediterranean conditions and ten years after the start of the experiment, SOC and N concentrations in the 0-30 cm soil layer were already higher in the NT system than in CT. Furthermore, the highest increases in SOC and N concentrations occurred in the surface layer (0-10 cm) and no differences were observed in the deeper layers between tillage systems. After 28 years, the initial values of SOC and N content under NT increased by 22% in the soil depth of 30 cm while in CT conditions they decreased by 3% and 5%, respectively. However, the mean gain of SOC and N contents under NT was mainly attributed to increases in the surface layer while in the soil layers of 10-20 and 20-30 cm the accumulation of SOC over time was negligible even under NT.

Since crop yields improvement as well as the reduction of production costs are crucial factors for increasing the profitability production, particularly in the regions where the extensive agriculture is mostly diffuse, long-term studies are needed to properly evaluate the effectiveness of alternative soil managements as the conservative agriculture but also in order to support the decisions of stakeholders for specific public funding to farms that want to switch to CA, promoting the conversion of farm machinery adapted to the CA [29].

A field trial of tillage and no-tillage, which began in the 1994-95 cultivation season in Southern Italy (Foggia, Puglia) at the CREACI (Council for research and agricultural economics - Research centre for cereals and industrial crops) and currently in progress, was performed to assess whether a durum wheat crop sown continuously for sixteen years would lead to changes in yields and its components, grain quality and some soil properties.

Materials and Methods

Description of experimental site

The trial has been started in 1994/’95 growing season and it is still in progress at the experimental farm (41°27’57” N; 15°30’20” E; 80 m a.s.l.) of CREA-CI of Foggia (Apulia, Southern Italy), a typically Mediterranean environment. The soil has a clay-loam texture and is classified as Typic Calcixerept [30]. Some properties of the soil profile are reported in Table 1.