Performance of eleven winter wheat varieties in a long term experiment on mineral nitrogen and organic fertilisation

Highlights

• Interactions between winter wheat varieties and fertilisation in a long term trial.

• Comparison of varietal responses to high, low and organic nitrogen inputs.

• Substitution of the mineral N with manure allowed to maintain yield and N content.

• Varieties could be discriminated by post-anthesis N accumulation.

• Varieties highly performing at high inputs tended to be good at low inputs.

Abstract

There is an increasing awareness about the need for improving nitrogen use efficiency in crop production in order to meet economic and ecological standards. The present work provides insight into the varietal factors of wheat that determine nitrogen use in the plant. The performance of eleven winter wheat varieties in terms of grain yield and nitrogen uptake and use efficiency was tested within the framework of a 40-year long term field experiment of organic enrichment and mineral nitrogen fertilisation treatments. Globally, organic enrichment had a beneficial effect on the yield and grain nitrogen concentration and showed a strong interaction with the amount of applied mineral nitrogen fertiliser. Manure application generally had positive effects on varietal performances mainly due to indirect long term effects on the soil properties. Varieties showed a broad range of responses to the treatments of the long term experiment, revealing significant genotype × environment interactions. Nevertheless, the varieties which performed well at high input levels were also the best at low input levels, suggesting that the genotype × environment interactions were not strong enough to inverse the performance ranking. Similarly, the varietal traits associated with high yielding or grain nitrogen concentration in high input conditions were the same as those identified under low input conditions. To conclude, these results suggest that the selection of wheat for nitrogen efficiency is possible under any nitrogen fertilisation regime. However, to be adapted to low input or organic agriculture, varieties also need traits other than nutrient use efficiency, for example, disease resistance, resilience to abiotic stresses and competitiveness against weeds.

Introduction

Nitrogen is one of the most important factors controlling crop development (Frink et al., 1999, Marschner, 1995). The increasing use of mineral nitrogen fertilisers has thus driven the explosion of crop production observed worldwide during the last century (Hirel et al., 2007, Ladha et al., 2005, Tilman, 1999). Yet, the overuse of fertilisers is a major source of environmental pollution, due to nitrate leaching and run-off (Huggins and Pan, 1993, Raun and Johnson, 1999). In addition, the fabrication of mineral nitrogen is costly and highly energy consuming. These drawbacks have motivated important changes in recent fertilisation practices, such as reduced nitrogen fertiliser use and the increasing interest in wheat varieties with elevated nitrogen use efficiency.

As crop development and performance are closely linked to nitrogen availability, the challenge resides in reducing the nitrogen input without affecting yield and quality. One possible approach to solving this problem is breeding varieties that use nitrogen more efficiently (Foulkes et al., 2009, Hirel et al., 2007, Sylvester-Bradley and Kindred, 2009, Tilman, 1999). Nitrogen efficiency of varieties can be described using the nitrogen use efficiency (NUE) approach (Van Sanford and Mackown, 1986, Sadras and Lemaire, 2014). Several studies have shown that the traits linked to the absorption and use of nitrogen, as well as to the formation of yield, are genetically determined and vary between genotypes and species (Austin et al., 1977, Barraclough et al., 2010, Barraclough et al., 2014, Bogard et al., 2010, Flood and Martin, 2001, Gaju et al., 2011, Le Gouis et al., 2000, Lemaire et al., 2008, Ye et al., 2011). Components of NUE are therefore potential targets for breeding of wheat varieties (Foulkes et al., 2009, Gaju et al., 2011). Yet, these traits are also subject to significant genotype × environment interactions. Therefore, breeding for nutrient use efficiency requires a good knowledge of the underlying genetic and environmental factors (Annichiarico, 2002, Ceccarelli, 1996). When decreasing the nitrogen input, or replacing mineral nitrogen with nitrogen from organic sources, the yield, quality and environmental performances of the varieties may change as a function of their genetic background (Ceccarelli, 1996, Charles et al., 2006, El Bassam, 1998, Ruiz et al., 2008, Vlachostergios and Roupakias, 2008). Today, varieties are usually selected under high or medium nitrogen conditions. Several studies suggest that traits selected under nitrogen rich conditions may not be the same as those required for high performance under nitrogen limiting conditions (Ceccarelli, 1996, El Bassam, 1998, Ruiz et al., 2008, Vlachostergios and Roupakias, 2008). Consequently, in order to improve nutrient use efficiency in wheat, the performance of genotypes under contrasting soil fertility conditions needs to be understood.

A few studies have investigated varietal responses when only very low nitrogen is available thus identifying useful genetic traits for low input systems (Dawson et al., 2008). Under most low input conditions, the seasonal course of nitrogen availability in soil is the determining factor of the progression of nitrogen accumulation in plants, followed by their capacity of N remobilisation from vegetative biomass and post-anthesis accumulation (Berry et al., 2002, Dawson et al., 2008, Masclaux et al., 2001). These processes may even be more important in production systems using organic amendments, because the release of organic nitrogen depends on the dynamics of mineralisation, which in turn depends on climatic and other environmental conditions. Chemical fertilisers, on the other hand, release nitrogen rather quickly. The release of organic nitrogen is therefore slow and spread over a longer period of time (Berry et al., 2002). In low input systems in stockless farms, soil organic matter decreases gradually on a long term perspective (Maltas et al., 2012b, Riley et al., 2008). Yet, the decrease in soil organic matter affects the dynamic of nitrogen availability in the soil. It is thus important to identify wheat genotypes able to cope with these conditions.

Consequently, there is a need to better select plants adapted to limited nitrogen conditions, to the form of its supply (mineral, organic), to its nature in soil (high, low organic matter content) and to the dynamics of its availability to the crop. For instance, it has been suggested that varieties absorbing nitrogen early in the season perform better in conditions with low nitrogen availability (Baresel et al., 2008). Breeding for nitrogen efficient varieties that perform well under nitrogen limiting or organic conditions has to account for the genetic basis of the crop but also all cultivation and environmental factors that influence the absorption and the allocation of nitrogen in the plant. This raises the question of the need for a specific breeding scheme for organic production methods as varieties have to cope with stronger stresses and higher environmental variability in contrast to high input systems (Lammerts van Bueren et al., 2002, Löschenberger et al., 2008, Müllner et al., 2014, Reid et al., 2011, Wolfe et al., 2008).

To address the question of varietal responses to low input and organic fertilisation, a study was made within a long-term field experiment of nitrogen fertilisation and organic enrichment, established in 1976 in Switzerland. This experiment offered the unique opportunity to study eleven European winter wheat varieties (Triticum aestivum L.) in unusually contrasting environments of different soil fertility within a single field and over two years. The objectives of this study were (1) to investigate the varietal responses to various sources and amounts of nitrogen fertilisation and various soil organic matter content in the same soil, (2) to better understand the agronomic traits that characterise the behavior of modern varieties under these different conditions, their capacity to exploit soil nitrogen mineralisation, and the dynamics of resource acquisition, (3) to evaluate the need to undertake specific selection for low input systems and (4) to identify the crucial traits necessary for the selection of best adapted varieties. For this, varietal responses in terms of yield, nitrogen content, nitrogen accumulation and nitrogen related traits were systematically explored.