Impact of sulfur applications on the agronomic performance of rapeseed–clover mixtures

Abstract

Rapeseed (Brassica napus L.) is a crop requiring high levels of nitrogen (N) fertilizer for growth and to optimize yield and seed quality. To limit the environmental pollution associated with intensive N fertilizer use, rapeseed–clover (Trititcum incarnatum L.) mixtures were grown in lysimeters under low N conditions (100 kg N ha−1). Considering the high sulfur (S) requirements of both rapeseed and clover, two inputs of S fertilizer (30 and 60 kg S ha−1) were applied. The effects S input on the agronomic performance of rapeseed in mixture and monocrops considered as reference, the N2‐fixing capacity of clover, and the leaching of nitrate and sulfate were monitored. This study showed that the N2‐fixing capacity (%Ndfa) of clover was improved (1.3‐fold) when it was grown in mixture with rapeseed at S60. However, irrespective of the type of cropping (monocrops or mixtures) and S application level (30 or 60 kg S ha−1), the biomasses and total N and S contents of both plants were not significantly different, nor was the rapeseed seed quality. Moreover, the yield of rapeseed grown in mixture at S60 was significantly lower than the yield of rapeseed grown as a monocrop (331.5 ± 9.8 versus 380.8 ± 3.5 g DW m−2, respectively). The results demonstrate that, in our field conditions, rapeseed mixed with clover required only 30 kg S ha−1 to maintain yield and seed quality, despite the high S needs of both plants. More surprisingly, compared to the rapeseed monocrop, the rapeseed–clover mixture led to an increase in N ( NO3 - ‐N) and S ( SO4 2- ‐S) leaching during the early winter period of cultivation.

Silicon Promotes Agronomic Performance in Brassica napus Cultivated under Field Conditions with Two Nitrogen Fertilizer Inputs

“…Seeds of rapeseed ( Brassica napus L. var. ‘Citizzen’) were sown (7 September, 2016) as previously described by Génard et al [21]. At stage B4 (after the appearance of the first 4 leaves), young plants were carefully transplanted into the lysimeters (2 m 2 of area), with a density of 60 plants per lysimeter.…”

“…Near infrared spectroscopy analysis was performed as previously described by Génard et al [21]. Briefly, intact seeds (5 g) were placed in a standard ring cup and were scanned on a near infrared monochromator spectroscopy system equipped with a transport module in the reflectance mode (model 65000, FOSS NIR System Inc., Silver Spring, MD, USA).…”

Silicon Supply Improves Nodulation and Dinitrogen Fixation and Promotes Growth in Trifolium incarnatum Subjected to a Long-Term Sulfur Deprivation

“…In conclusion, the results of this study suggest that Si fertilization could be considered as part of emerging agroecological and agricultural practices to optimize fertilizer inputs. For example, to reduce the quantity of N inputs applied during Brassica napus crop growth, several recent studies have explored mixed cropping of this plant with legume species [ 49 ], and in particular with Trifolium incarnatum [ 18 , 33 ]. Indeed, the high sulfur requirements of Brassica napus for growth can decrease the availability of S in the soil and lead to decreases in the N 2 fixation capacity of the companion legume.…”

“…Finally, due to the decrease in seed quality, sulfur deficiency has indirect negative impacts on the health of human and animal consumers [ 17 ]. Currently, use of S fertilizers at a dose of about 30 kg S ha −1 [ 18 ] is the most widely used strategy to support S deficient crops. However, in the global agroecological context of reducing inputs, it is urgent that other strategies be developed to alleviate the stress of plants experiencing S deficiency.…”

“…In this study, we focused on Trifolium incarnatum because previous studies have shown that this legume species is of agroecological interest especially when it cultivated in mixed crops. For example, in Trifolium incarnatum - Brassica napus intercrop, several works recently report shown that the transfer of nitrogenous compounds from clover to rapeseed improved the agronomic performance of this field crop [ 18 , 33 , 34 ].…”