Abstract
Fungicide intensity and sowing time influence the N use efficiency (NUE) of winter wheat but the underlying mechanisms, interactions of plant traits, and the temporal effects are not sufficiently understood. Therefore, organ-specific responses in NUE traits to fungicide intensity and earlier sowing were compared at two nitrogen (N) levels for six winter wheat cultivars in 2017. Plants were sampled at anthesis and at maturity and separated into chaff, grain, culms, and three leaf layers to assess their temporal contribution to aboveground dry matter (DM) and N uptake (Nup). Compared to the control treatment, across cultivars, the treatment without fungicide mostly exerted stronger and inverse effects than early sowing, on grain yield (GY, −12% without fungicide, +8% n.s. for early sowing), grain Nup (GNup, −9% n.s., +5% n.s.) as well as on grain N concentration (+4%, −2% n.s.). Grain yield in the treatment without fungicide was associated with similar total DM, as observed in the control treatment but with lower values in harvest index, thousand kernel weight, N use efficiency for GY (NUE) and N utilization efficiency. Lower GNup was associated with similar vegetative N uptake but lower values in N translocation efficiency and N harvest index. In contrast, early sowing tended to increase total DM at anthesis and maturity as well as post-anthesis assimilation, at similar harvest index and increased the number of grains per spike and total N use efficiency. Total N uptake increased after the winter season but was similar at anthesis. Although the relative N response in many traits was lower without fungicide, few fungicide x interactions were significant, and the sowing date did not interact either with N fertilization for any of the N and DM traits. The results demonstrate the positive effects of fungicides and earlier sowing on various traits related to yield formation and the efficient use of nitrogen and are discussed based on various concepts.
Highlights
Wheat contributes about 20% to the global calorie and protein production, but substantial advances in grain yield (GY) are required to meet the rising demand of a growing population with its altered consumption patterns [1]
Cultivar effects were significant in the whole trial as well as in both trial subsets with the exception of N concentration (NC) of flag leaf-1 at maturity (Mat.), grain N uptake (Nup), N utilization efficiency (NutEff) at anthesis and total N use efficiency (NUE), and only few other traits within both trial subsets
Among direct dry matter (DM) traits, the main plot treatments showed an effect for the whole trial for anthesis DM only for ‘other leaves’, at maturity most strongly for grain DM (GY) in the whole trial and in Cont + reduced fungicide (RF), for DM of culms both in the whole trial and in Cont + RF, for ‘other leaves’ in the whole trial, and in Cont + sowing date 1 (SD1) and for the total above-ground DM only for the total trial
Summary
Wheat contributes about 20% to the global calorie and protein production, but substantial advances in grain yield (GY) are required to meet the rising demand of a growing population with its altered consumption patterns [1]. Efficient nitrogen (N) use, both in N-limited environments for stabilizing yields and in regions where high amounts of N fertilizers lead to detrimental environmental effects, is a major challenge to be addressed [2,3]. On the one hand, breeding progress increases N use efficiency (NUE) [4,5] through exploiting present genetic variation in NUE [6] and contributes to selecting suitable cultivars for specific growing regions [7]. Agronomic measures must be optimized and adapted for modern cultivars This includes optimal sowing densities and seed placement [8], sowing date [9,10], adapted timing and dosing of N fertilizers [11,12] as well as optimum fungicide strategies [13,14].
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