​Effect of Date of Sowing on Growth, Seed Yield and Economics of Indian Mustard (Brassica juncea) Varieties under Rainfed Conditions

Indian  mustard  (Brassica juncea)  is  the  second  most important oilseed crop in India after groundnut sharing 27.8%  in  the  India’s  oilseed  production. The crop occupies an area of 8.74 m ha, with the production of 10.95 m tons and average productivity of 1270 kg/ha in the country (Anonymous, 2022). Haryana state also contributes 10.2% to the total rapeseed-mustard production in the country.  Indian mustard is an important rabi crop raised under rainfed areas of Haryana but also in adjoining Rajasthan. High probability of irregular monsoon not only jeopardizes the kharif production but rabi crops also due to inadequate moisture storage in the soil profile. In the last decade, against the normal precipitation of 54.9 mm rainfall during rabi season, the values differed every year due to change in climatic conditions. Indian mustard also suffers from frost at maturity phase and yields are drastically affected in winter season. Adoption of improved varieties and their timely sowing are important factors for improving their productivity. Different cultivars may respond differently to different sowing time (Rajput et al. 1991).

Time of sowing is very important for crop production as different sowing dates provide variable environmental conditions within the same location for growth and development of crop. Growth and yield of Brassica species largely depends upon change in environment during crop growth and this change  in  environment  can  occur  through  many practices  including  sowing dates  and  water availability. For getting higher yields, sowing time of crop needs to be adjusted with suitable agro climatic environment (Saha and Khan, 2008). Pradhan et al. (2014) reported that there was significant interaction between date of sowing and cultivars with respect to seed yield of mustard. Indian mustard is much sensitive to climatic variables. Hence climate change could have significant effect on its production. Planting window and mustard cultivars is the most important element realizing potential yield of crop. Generally, the time of planting varies depending on the climatic condition of the region and the variety to be grown. Different varieties of mustard are sensitive to change in environmental conditions where the crop is being grown. Delayed sowing owing to change in biotic and abiotic environmental conditions may have adverse affect on crop performance. Sowing time is also one of the most important non-monetary input which influences to a great extent on both the productivity of seed and oil of Indian mustard under rainfed conditions (Shekhawat et al. 2012). On the other hand, sowing time of Indian mustard was determined long back but therefore, the fertility status, varieties and other inputs have inadequate a considerable change, so there is a need to give fresh look for time of sowing of Indian mustard in the light of introduction of new varieties. Hence, keeping in view the importance of Indian mustard as a major oilseed crop of the state, the present study was investigated to find out the best time of sowing and suitable variety for mustard under rainfed conditions.

Field experiments were conducted at Dryland Agriculture Research Farm, Chaudhary Charan Singh Haryana Agricultural University, Hisar during 2018-19 and 2019-20 (20°-10’ N, 75°-46’ E and 215.2 m above mean sea level). The sandy loam soil of the experimental field was low in organic carbon (0.27%), available nitrogen (120 kg/ha), medium in available phosphorus (12.4 kg/ha) and available potash (262 kg/ha) with 7.3 pH. The experiment comprising of 3 dates of sowing (16 October, 23 October and 30 October) and 4 varieties of Indian mustard (RH 725, RH 761, RH 406 and RH 30) was laid out in split plot design. The sowing dates were allocated in the main plots and varieties in the sub-plots and were replicated thrice. A basal dose of 40 kg N + 20 P2O5/ha was applied at the time of sowing. The row spacing was 45 cm keeping 5 kg seed rate/ha. The other agronomic practices were followed as per production recommendations during the crop growth period. Rainfall (October-March) and other climatic data were recorded during the course of experimentation.

The observations on plant height and number of branches per plant were recorded manually on five randomly selected representative plants from each plot of each replication separately as well as yield and yield attributing characters were recorded as per the standard method. Yield attributes were also recorded at physiological maturity stage. The economics of the treatments was worked out considering the prevailing cost of inputs and outputs (₹4312/qtl for mustard seed and ₹75/qtl for mustard stover/stalk). All the results were then analyzed statistically for drawing conclusion using Analysis of variance (ANOVA) procedure. Since similar trends were noticed during both the years, the data pertaining to both years were pooled.

Weather and climate
 
The data on rainfall was recorded by the rainguage located at the experimental site (Table 1). The total rainfall received during the crop growth period was 46.2 and 167.5 mm while during rabi season (Oct-Mar) it was 46.2 and 173.0 mm during 2018-19 and 2019-20, respectively with average value of 109.6 mm, which was 100 per cent higher over the mean normal rainfall (54.6). Month wise it was 171, 79 and 385% higher in November, January and March and 70, 37 and 17% deficit in October, December and February over the mean monthly normal rainfall, respectively. More or less variations among the rest of the climatic data compared to long term average were also observed (Fig 1). During both the seasons, the mean maximum and minimum temperature ranged from 24.8-25.9 and 10.9-15.5°C, respectively. The relative humidity varied from 49 to 53% in the evening to 89 to 91% in the morning. The average wind speed ranged from 3.3 to 3.7 km/hr. The bright sun shine hours ranged between 5.1 on a cloudy day to 5.5 on a clear day. Evaporation from open pan evaporimeter ranged between 2.2 to 2.3 mm/day.




 
Effect of date of sowing
 
Date of sowing brought significant variation on growth, yield attributing parameters, seed and stover yield of Indian mustard (Table 2). Crop sown on 23^th October produced significantly taller plants being at par with sowing on 16^th October over 30^th October sowing. Higher number of branches per plant and test weight was recorded when planting was done on 16^th October compared to 23^th October and 30^th October sowing. However, difference between 16^th October and 23^th October sowing was found to be at par. Yield attributes viz., number of siliquae per plant and number of seeds per siliqua was significantly increased when mustard was sown on 16^th October compared to 23^th October and 30^th October sowing. Similar results were also observed by Singh et al. (2017). Seed and stover yields showed significant difference among sowing dates. The highest seed yield in 16^th October sown crop was also due to significantly improved yield attributes as compared to crop sown on other dates. Maximum seed yield was recorded in 16^th October (2499 kg/ha) as compared to 23^th October (2277 kg/ha) and 30^th October (2032 kg/ha). The reduction in yield by delay in sowing by successive week after 16^th October was 8.9 and 18.7%. The highest yield may also be due to the prevalence of most favourable temperature at sowing time (16^th October) and longer optimum period for crop growth (Fig 1). The late planted crop is subjected to relatively lesser time span available for plant growth and development. Further monthly rainfall distribution pattern during the crop seasons of 16^th October sown crop showed that comparatively higher rainfall was received during November and January commentating vegetative and flowering stage of the crop, however normal rainfall was received during the month of February commentating siliqua formation stage of the crop which helped in terms of increased seed and stover yield. These findings are in close conformity with those of Kumar et al., (2017) and Tripathi et al. (2021). The 16^th October (24.7) sown crop recorded highest harvest index as compared to 23^th October (23.6) and 30^th October (24.6). Rain water use efficiency was found highest in 16^th October (39.88 kg/ha-mm) sowing compared to other dates of sowing.
 


Effect of varieties
 
All the varieties tested under different dates of sowing differed in respect of growth, yield and yield parameters (Table 2). The maximum plant height (180.5 cm) was recorded for RH 725 which was significantly superior to other varieties except RH 761. Number of siliquae per plant and seeds per siliqua were found to be significantly higher with variety RH 725 compared to other varieties. Mustard variety RH 30 recorded higher test weight compared to other varieties and was at par with RH 725. This is because of variation in different genotypes in their genetic makeup. The seed yield of mustard mainly depends on the number of siliquae per plant, number of seeds per siliqua and test weight as these characters have high degree of positive correlation with seed yield. The variety with RH 725 produced higher value of seed and stover yield which was significantly higher to RH 30, RH 406 and RH 761. Such varietal differences with respect to yield have been reported by Ranabhat et al., (2021) and Panwar et al. (2000). Harvest index and rain water use efficiency was found highest in RH 725 compared to other varieties of mustard. Interaction of sowing date and varieties was not significant.
 
Economics
 
The crop sown on 16^th October provided higher net returns (₹92674/ha) as well as B:C ratio (5.23) and it was 12.1 and 30.7% higher over 23^th October and 30^th October sowing, respectively. This is because of higher seed and stover yield in 16^th October sowing compared to other dates of sowing. Indian mustard variety RH 725 proved its superiority with 19.2, 36.8 and 18.9% higher net returns over RH 761, RH 406 and RH 30, respectively. This is again because of higher seed and stover yield for RH 725 variety compared to other varieties. These results are in agreement with the results of Singh et al. (2018) and Bikshapathi (2021).

Based on two years performance it can be concluded that Indian mustard can be sown by October 16 for higher yields and RH 725 variety proved to be highest yielder under rainfed conditions of sandy loam soils in arid/semi arid regions.