Studies on the effect of nitrogen fertilizer, row spacing and use of antitranspirants on rapeseed (Brassica campestris) grown under dryland conditions

Abstract

SUMMARYAn experiment is desoribed which was conducted for 2 years under dryland conditions of north-west India to evaluate the optimum rate of application of N fertilizer and plant population density for a rapeseed crop. Stomata closing (phenyl mercuric acetate), film forming(Mobileaf) and reflective type (kaolinite) antitranspirants were used to examine their effectson conservation of stored moisture for a possible increased water use efficiency under drylandconditions.The rapeseed crop responded to N fertilizer and it was profitable to use 53 kg N/ha xinder these conditions. In a drier year a wider row spacing of 60 cm (1·1 x 106 plants/ ha) was significantly better than narrower spacing of 30 cm (2·2 xlO5 plants/ha). Plants grown in wider row spacings utilized less water during the vegetative and flowering stages than those grown in closer spacings.The relative water content of leaves sprayed with antitranspirants was greater than in the control plants. The leaf temperature of the kaolinite-treated canopy was 1·5 °C lower than the ambient air temperature. Averaged over 2 years, the film-forming antitranspirant Mobileaf increased the seed yield by 26% while spraying with phenyl mercuric acetate at 50 and 75 days and kaolin application at 50 days increased the rapeseed yield by 11, 18 and 17% over the no antitranspirant treatment.

In-field film antitranspirant application shows potential yield protection from flowering-stage drought periods in winter canola (Brassica napus)

“…In these experiments the control un-irrigated and un-treated showed a lower seed yield than in our work on average (1.60 t ha -1 ). The lower seed yield found by Patil and De (1978) when compared to our work may be for two reasons. First, the crop was a spring variety, and it is well known that spring varieties generally exhibit lower yield than the winter crop.…”

“…Application of film antitranspirant has been previously used in a broad range of crops to mitigate drought induced yield losses (e.g on sorghum in Fuehring, 1975) and recently in fieldgrown wheat (Weerasinghe et al 2016) and pot-grown oilseed rape (Faralli et al 2016;Faralli et al 2017a). There is only one publication available testing the efficacy of different AT to avoid yield losses on a crop belonging to the same BN family (Brassica campestris) (Patil and De, 1978). Mobileaf (the film forming chemical), increased seed yield irrespective of the N supply in both years with an average of 0.41 t ha -1 following an ameliorative effect on plant water status.…”

“…BN has been shown to be more drought sensitive than wheat (Hess et al 2015) and AT application around flowering was beneficial for the yield of pot-grown BN subjected to water stress, although a substantial difference in efficacy between two AT was recorded (Faralli et al 2016). Application of AT on field-grown Brassica campestris gave a grain yield increase following improved plant water status and water-use efficiency under dryland conditions De, 1976 and1978). However, no additional work has been published on field experiments so far and there is no work in the literature investigating the effectiveness of film antitranspirants at avoiding winter BN yield losses under drought conditions in the field.…”

Yield enhancement of droughted wheat by film antitranspirant application: rationale and evidence

“…Despite a reduction in photosynthesis, increased growth in size of stem internodes through cell expansion was found following antitranspirant application. Further support is found in reports of yield enhancement from film antitranspirants applied at or near the time of sensitive stages in other seed crops from the early years of antitranspirant research, including sorghum [17], rapeseed [18] and corn (maize) [19]. More-recently, such reports have been cited to cast doubt on the conclusion in reviews and textbooks of limited usefulness of film antitranspirants [20].…”

Modulation of Brassica napus source–sink physiology through film antitranspirant induced drought tolerance amelioration that is dependent on the stress magnitude

“…Similarly, the lower CO 2 assimilation rate found under WW + AT conditions when compared to WW-AT suggests that AT may decrease the amount of assimilates translocated from the source to the sink, thus reducing the carbohydrate available for seed development under optimal conditions for plant growth. Significant increases, however, with respect to the ÀAT plants were found under WS and SWS conditions confirming the capacity of the AT to sustain yield under drought in OSR(Faralli et al, 2016;Patil & De, 1978). However, in SWS plants, only seed MWS, WS and SWS watering regimes over flowering stage and treated with water or 1% v/v AT.…”