Effect of weather parameters on growth stages of winter maize ex- plain the grain yield

A study was conducted on research farm of National Maize Research Program (NMRP), Rampur, Chitwan, Nepal during winter season of 2015/16 laid out in split-split plot design with three replications consisting of two FYM levels (FYM at 10 t ha-1 and no FYM application), three nitrogen levels (100, 75 and 50% N of recommended dose P and K remaining constant) and two levels of seed inoculation (Azotobacter chrococcum seed inoculation and no inoculation) with Rampur-2 maize hybrid in Nepal. One of the major factor affecting maize production is weather and this paper is prepared to assess the suitability of weather condition at different growth stages of winter season hybrid maize in condition of western Chitwan, Nepal at NMRP. The result shows that the requirement of the maize crop during different growth stages i.e. temperature, rainfall, relative humidity were fulfilled which helped to obtain remarkably higher grain yield (4.26 t ha-1) in the experiment compared to average national grain yield (2.84 t ha-1) of maize.


Introduction
Maize (Zea mays L.) can be grown easily in any season and is important cereal crop due to fast growing nature, higher yield, palatability and nutritiousness resulting easily accessible food and feed for humans as well as animals [1]. In Nepal maize is grown as a staple food crop for many years. In terms of area and production, maize ranks second to rice [2]. It shares about 6.54 % in Agricultural Gross Domestic Product (AGDP). Maize can grow in a wide range of environment; however, warm climate with temperature ranging from 21 to 30°C is most favorable [3]. Moreover, it was reported [4]that maize growth is best with temperature between 18°C and 27°C during day time and around 14°C at night. The experimental site falls under the sub-tropical humid climatic belts of Nepal with three distinct seasons i.e. November to February (winter), March to May (hot spring) and June to October (rainy). The maximum temperature during the coldest month of year (December to February) reaches to 27°C whereas the minimum temperature during this period ranges from 6 to 10°C. Likewise, the maximum temperature during hottest month of year (May to June) is measured up to 42°C. Recent studies conclusively proved that maize is a potential winter season crop having three times higher yield potential than kharif crop [5]. According to annual report of NMRP [6], the productivity of winter maize is about 6-7 t ha -1 while that of summer maize is around 4.0 t ha -1 .

Dahal et al., 2021
Effect of weather parameters on growth stages of winter maize explain the grain yield The mean annual temperature trend at Rampur, Chitwan during 1968 to 2008 showed that the increase of temperature seemed to be more in the recent decade than the former decade and the trend was 0.039°C per year [7]. Thus the changed weather condition can create impact upon the maize production as yield of maize is primarily influenced by sunlight, temperature, available plant nutrients and water supply [8]. One of the major factors affecting maize production is weather and this paper is prepared to assess the suitability of weather condition at different growth stages of winter season hybrid maize in condition of western Chitwan, Nepal at NMRP. and two levels of seed inoculation (Azotobacter chrococcum seed inoculation and no inoculation) as sub-sub plots. Farm Yard Manure (FYM) was applied two weeks before sowing and was incorporated into soil. Chemical fertilizers: urea, single super phosphate (SSP), diammonium phosphate (DAP) and muriate of potash (MOP) were also applied as main source of nitrogen, phosphorus and potassium, respectively. Urea was applied in three splits; at sowing, knee high and tasseling stages. Azotobacter was applied as seed inoculation preparing of slurry of 10% sugar solution mixing 100 gm of sugar on 1000 ml of water and was boiled and azotobacter were applied after cooling on shade.

Materials and Methods
Harvesting was completed on March of 2014, from net plot area.
Weather data were collected from meteorological data center near (100m) the research field.

Weather condition during the experimentation
The experiment field receives regular precipitation of 1919.5 mm (NMRP, 2015/16).The average weather parameters regarding minimum as well as maximum temperatures, relative humidity and total rainfall are presented at an interval of two weeks in Figure 1. The weather condition during the period of experi-mentation presented in the Figure 1 and Table 1 shows that the higher value of maximum temperature (33.85°C) was recorded on 1st week of September which gradually declined up to 3rd week of December (21.1°C). Thereafter, it increased up to 24.69°C on 1st week of January and then declined to 21.05°C on 4th week of January. Further, the values of maximum temperature were found to increase up to 32.84°C on 2nd week of March and then remained at the same level at the 4th week of March (32.51°C).

Results
Analyzed data of phenological stages (  [11] reported that optimum temperature for vegetative phase ranges from 28 to 34°C. Venkataraman and Krishanan [4] also mentioned that range of temperature for the growth of maize is from 9°to 46°C with the optimum around 34°C during vegetative growth stage.
Thus, the minimum temperature was found higher but maximum temperature was slightly lower due to winter season. However, it was close to the temperature given by Joshi [11]. Moreover, in the experimental site, the average temperature during tasseling and silking stages equaled to 19.07°C. With respect to it, Venkataraman [12] reported that the optimum temperature for tasseling ranges from 21 to 30°C and temperatures above 32°C during reproductive stage reduced the yield. Thus average temperatures during tasseling and silking were close to optimum level.
Further, minimum and maximum temperatures during these stages were 13.75 and 24.39°C, respectively. In respect of it, Berbecel and Eftimescu [13], mentioned that the maximum temperature above 32°C around tasseling and pollination increases the differentiation process of the reproductive parts and conse- week before germination, respectively ( Figure 1) which provided enough moisture for germination of maize seeds. Moreover, a rainfall of 8.3mm was recorded at sowing which also helped in better germination of seeds. Germination of maize seed was completed within 6 days.
No rainfall was recorded during knee high and grand growth stages. Others [10] stated that moisture stress in early growing season causes a large reduction in grain yield. Therefore, the experimental plots were irrigated at this stage. Kranzet al., [14] Dahal et al., 2021 Effect of weather parameters on growth stages of winter maize explain the grain yield mentioned that corn requires most of the water during the early reproductive growth stages i.e. tasseling and silking.
Moreover, the requirement of maize in water is more prominent during the tasselling to silking stage [15] which is considered critical as grain formation initiates during this period. Thus the availability of soil moisture at the time of tasselling is therefore vital for the production of high yield in maize [16].
Futher, period of silking and ear growth the corn is most sensitive to moisture deficiency as far as the grain yield is concerned [4]. However, there was no rainfall during this period in the experimental site due to which the crop was irrigated at this phase.
Another critical period with respect to crop requirement in moisture is grain filling period. Corn requires one third part of seasonal water requirement at beginning of dough stage. Drought or water stress at dough stage results in acceleration of maturity preventing grains from gaining full size as well as weight [14].
However, there was 7.7 mm rainfall during grain filling period and 0.96mm at dough stage which might had helped to some extent fulfill the crop requirement in water.
Thus, in general, the requirement of the maize crop in water was fulfilled either through rainfall or irrigation which helped to obtain remarkably higher average grain yield (4.26 t ha -1 ) in the experiment as compared to average national grain yield (3.09 t ha -1 ) of maize (MOAD-ABPSD, 2015). It concludes from above discussion that weather recorded during different key growth stages of winter maize in the experimental site were resultant and it is essential to give emphasis on weather conditions in improvement of grain yield of winter maize.