Productivity, nutrient use efficiency, energetics and bio-economics of winter maize in south India


 Maize area is rapidly spreading in south India in response to rising demand from the poultry and fish feed industries. The planting of maize during winter season is necessary to increase the total area and production of maize. The present investigation encompassing different sowing windows with different fertility levels revealed that significantly higher winter maize productivity was achieved from first and second week of October planting along with application of 200 % RDF(recommended dose of fertilizer) followed by 150 % RDF. Planting of winter maize during first week of October recorded significantly higher grain yield (8786 kg ha-1) and stover yield (1220 kg ha-1) and was found on par with sowing during second week of October. Among fertility levels, significantly higher grain yield (8320 kg ha -1) and stover yield (1195 kg ha-1) were recorded with application of 200 % RDF and was found on par with application of 150 % RDF. Similarly higher dry matter production, more days for physiological maturity, higher accumulation of growing degree days, photo thermal units and heliothermal units were recorded from crop planted during first and second week of October along with application of either 200 % or 150 % RDF. Further higher nutrient use efficiency was recorded from first and second week October planted crop along with lower fertility level (100 % RDF). Similarly significantly higher output energy, net energy and specific energy were higher from crop planted during first week of planting along with application of 200 % RDF. Also it recorded higher net returns and gross returns Whereas, energy use efficiency and energy productivity were higher with planting during first week of October along with application of 100 % RDF.

It is currently grown on 9.38 million hectares with a yield of 28.752 million metric tons 2 .Because of its photo-thermo-insensitive nature and highest genetic yield potential among cereals, maize is known as the "Queen of Cereals." . Corn is grown all year round in India, in most states, for a variety of purposes including food, feed, fodder, green cobs, sweet corn, baby corn, pop corn, and industrial goods.There are three distinct seasons for the cultivation of maize in India viz., Kharif, rabi in peninsular India and Bihar, and spring in northern India. Maize is predominantly a kharif season crop but in past few years winter maize has gained a significant place in total maize production in India 3 .
Winter maize is grown on an area of 1.697 m ha with a production of 8.302 million metric tons and with a productivity of 4893 kg ha -1 4 . The predominant winter maize growing states are Bihar (26.3 %), Tamil Nadu (13.1 %), Maharashtra (12.9 %), West Bengal (12.4 %), Andra Pradesh (9.5 %), Telangana (6.9 %) and Karnataka (6.4 %) 4 . It has emerged as an important crop in the non-traditional areas. While the crop responds favorably to better crop management in both the kharif and winter seasons, the irregular rainfall pattern of the south-west monsoon interferes with timely field operations of the kharif season. Due to the lack of significant environmental impediments in winter, the desired field operations can be scheduled and carried out at the most suitable time. In addition, lack of any major diseases and insect pests in this season, are helping the crop to express its potential. There is therefore an enormous opportunity to increase the area under cultivation of winter maize for higher productivity 3 . For winter maize, the best sowing date is essential so that the genotype grown can complete its life cycle under ideal environmental conditions. Planting at the beginning of the growing season is generally recommended. Sowing at the right time is critical for maximum yield, as a delay in the planting date would result in a linear decrease in grain and stover yields 5 . The amount of yield reduction caused by delayed sowing, on the other hand, varies by location. Hence experiment was conducted to explore the most congenial sowing period in Southern India.
The availability of sufficient nutrient in the soil in available form for plant uptake determines crop plant growth and yield 6 . There are a several of other factors that influence winter maize production and productivity; however, fertiliser management is one of the most important factors influencing maize growth and yields. Early maize planting can improve grain yields significantly, but other practises such as fertility can also trigger the yield 7 .
In agriculture, energy usage has intensified as a result of increasing population, a limited supply of arable land, and a demand for a higher standard of living 8 . It is critical to create a production system that uses less energy and produces more energy as output in the context of changing global climatic conditions and increasing energy demands 9 . In this experiment, all of the inputs and outputs were considered to be in the form of energy. Human labour, animal power, fertiliser, gasoline, and electricity are all used in some way in agricultural operations 10 .All the inputs supplied and output obtained is considered in the form of energy. Power, electricity, machinery, seeds, fertilisers, and chemicals account for a significant portion of the existing agricultural production system's energy supply. One of them is fertiliser control with care. Since, on the one hand, it accounts for more than half of the total input energy used in the maize production system in many cases, and on the other hand, it is the most important factor for proper plant growth and development. However, if it is used excessively in such cases, it can pollute rivers and streams, as well as cause greenhouse gas emissions. As a result, excessive deployment, wastes resources and money while also exacerbating environmental problems 11 . Fertilizers, with a energy equivalency of 51.5 percent, were found to have the highest rate of energy equivalency among all the inputs used in maize production 12 Planting window is one of the non-monetary input. Planting a crop at the right time increases not only the biological yield but also the profitability. It is important to investigate the required level of fertility and planting window in order to achieve long-term sustainability in winter maize production

Experimental site
During the winter season 2019-2020, a field experiment was conducted to investigate the response of winter maize to planting windows and fertility levels at the University of Agricultural Sciences, Dharwad (Karnataka), which is located at 15°26' N latitude and 75°07' E longitude with an altitude of 678 m above mean sea level (MSL). The research station is located in the Northern Transitional Zone (Zone-8), which is located halfway between the Western Hilly Zone (Zone-9) and the Northern Dry Zone (Zone-9) (Zone-3). The soil is classified as clay by the USDA soil textural classification table. The pH of the soil was 7.6, which was neutral. Available nutrients such as nitrogen were low (261 kg ha-1) and phosphorous (31.5 kg ha-1) and potassium (289 kg ha-1) were medium.

Treatment details
The experiment was conducted in a Factorial Randomized Complete Block Design

Cultivation method
To bring the soil to fine tilth, the field was ploughed once, followed by tillage with a cultivator and harrowed twice. After the previous crop was harvested, weeds and remaining residues were removed from the experimental field. The plots were set out according to the experiment's layout design. Seeds were planted at a 60 cm x 20 cm spacing with a seed rate of 20 kg ha-1. With the aid of a marker, the lines were opened, and the seeds were hand-dibbled at a depth of 4-5 cm before being covered with soil. All other treatment plots, including control plots, had well decomposed FYM @ 10 t ha -1 incorporated into soil two weeks prior to planting.The nutrients viz., nitrogen, phosphorus and potassium were applied @ planting to check the weed growth and to keep the plots free from weeds during the cropping period in all the dates of planting. With a spray of proclaim @ of 0.5 g litre-1, the crop was protected against fall army worm and stem borer. For all planting dates, the rainfall obtained during respective planting windows provided ample soil moisture for germination, emergence, and early establishment of seedlings. Rainfall fell during the crop growth cycle in the months of October (323.2 mm) and November (21.0 mm), and the rest of the season's crop was irrigated using the critical stage method. Since the experiment was conducted entirely under irrigated conditions, the crop did not experience moisture stress during the growing season.

Growing degree day (GDD)
Growing days were determined in this study by simply adding up daily mean air temperatures above a given threshold or base temperature. It can be expressed mathematically as follows: -Base temperature 10 °C (Narcico et al. 13 )

Photothermal units (PTU)
The photothermal units for a specific day represent the product of GDD and length of the day. Photo thermal units were calculated by using the equation given by Wilsie 14 .

Heliothermal Units (HTU)
The heliothermal units for a specific day are the product of multiplying GDD by the number of hours of bright sun that day. The tape in the Campbell-Stroke sunshine recorder burns when the strength of sunlight reaches a pre-determined threshold. The burn trace's total duration is equal to the amount of bright sunlight hours15. The formula was used to measure the total HTU for each phenophase's length Accumulated HTU (°C day hr) = GDD × Bright sunshine hours (hrs)

Nutrient use efficiency
The sum of product produced per unit of resource used is referred to as NUE. The amount of dry matter generated per unit of nutrient applied or absorbed is the mean nutrient efficiency. NUE is the difference between a genotype's yield on deficient soil and its yield at optimum nutrition 16. Agronomic efficiency, physiological efficiency, and recover efficiency 17  RE (%) = Nutrient uptake of the F plot -Nutrient uptake of the A plot × 100 Quantity of nutrient applied

Bio-economics
The price in USD of the inputs prevailed at the time of their use was considered for working out the cost of cultivation per hectare treatment wise and expressed in USD ha -1 . A gross return per hectare was calculated by taking into consideration of the price of the product that prevailed in market after harvest and grain yield per hectare and expressed in USD per hectare (USD ha -1 ). The net return per hectare was calculated treatment wise by subtracting the total cost of cultivation from gross return and expressed in USD per hectare (USD ha -1 ).
Net return (USD ha -1 ) = Gross return (USD ha -1 ) -Cost of cultivation (USD ha -1 ) The benefit cost ratio was calculated as follows.
Benefit cost ratio (B-C) = Gross return (USD ha -1 ) Cost of cultivation (USD ha -1 ) Note-Indian rupee was converted using a 70 INR for 1 USD rate.

Energetics
All the agricultural inputs such as seeds, fertilizers, labour, animals, electricity, machinery, organic manures etc. and all the agricultural outputs such as grain and straw have their own equivalent energy (Mega Joules) values ( Table 1). The energy balance was calculated using the data on input energy, output energy. From these, the net energy returns, energy use efficiency, energy productivity and specific energy were calculated using the following formulae [19][20][21][22][23] .

Statistical analysis and the interpretation of data
Fisher's method of analysis of variance, as outlined by Gomez and Gomez36, was used to statistically analyse the data collected at various stages of crop development.
The data was analysed with the MSTAT-C statistical programme, and the means were The accumulated GDD, PTU and HTU were significantly differed due to planting windows (Table 2)

Grain and biomass yield
Planting during 1 st week of October recorded significantly higher grain yield and stover yield (8788 and 1220 kg ha -1 respectively) and it was on par with planting during 2 nd week of October (8644 and 11980 kg ha -1 respectively) ( Table 3 and  week of November planting along with 200 % RDF (3.85 MJ kg -1 ).

Bio-economics
Significantly higher gross return, net return and B-C ratio was recorded with planting during 1 st week of October (USD 2,331 ha -1 , USD 1,409 ha -1 and 2.53 respectively) and it was on par with planting during 2 nd week of October (USD 2,293 ha -1 , USD 1,371 ha -1 and 2.49 respectively). Among fertility levels, significantly higher gross return, and net return were recorded with application of 200 % RDF (USD 2,211ha -1 and USD 1,231 ha -1 respectively). There was no significant effect observed with respect to B-C ratio among fertility levels (  (Table 3 and Fig. 2). Higher grain yield obtained from October 1 st week planting was attributed to significant improvement in yield characters and dry matter accumulation (Fig.1a). Similar results were also obtained 38 . Late planting would lead to a lesser row number and less grain numbers in the rows of maize 38 . Further, increase in grain yield and yield attributes in first week of October planting was due to improved growth parameters viz., number of green leaves per plant, leaf area, leaf area index, total dry matter production (Fig. 1a), absolute growth rate (AGR) and crop growth rate (CGR) as a result of higher accumulation of growing degree days (GDD), photothermal units (PTU) and heliothermal units (HTU) compared to delayed planting (  (Table 2) which reduced the vegetative growth, dry matter accumulation (Fig. 1a) and finally the yield 42,43 . Environmental changes associated with different planting windows (sunshine and temperature) have a modifying effect on growth and development of maize plants 41 . In early planted maize, better photosynthesis was observed as evidenced by more leaf area index and accumulation of photosynthetes due to favourable climatic conditions 45 .
Late planting brings horse weather parameters such as temperature, solar radiation, humidity during crop season which adversely affect the morphology, plant physiology and molecular level of plants 46 .

Productivity of winter maize as influenced by fertility levels
Application 200 % RDF increased the grain yield by 3.71 and 10.98 per cent compared to 150 % and 100 % RDF respectively (Table 3 and Fig.1b). The increased grain yield was due to improved yield attributes. Among several inputs essential for crop production, fertilizer management is of superlative importance. Further improved yield attributes was due to increased leaf area, leaf area index and total dry matter production (Fig. 1b). Steady increase AGR and CGR also play important role towards yield. Increased growth and yield parameters in 200 % RDF were also due to higher available nutrients and their uptake 47 . These results are conformity with the findings of Sreelatha et al. 48 .
They reported higher yield and it's parameters in higher fertilizer levels  (Table 3 and Fig.1c). and planting during 1 st week of October along with application of 150 % RDF (W 1 F 2 ). The increased grain yield and stover yield was due to improved yield attributes. Increase in yield and yield attributes was due higher growth in terms of number of green leaves per plant, leaf area, leaf area index and total dry matter production (Fig. 1c) which increased AGR and CGR. These results are similar with findings of Verma et al. 51 and they reported early planting and higher fertilizer levels favours good plant height, leaf area index and dry weight per plant due to favourable climatic conditions especially temperature which increased metabolic activities, increased assimilation and cell division within the plant. Increased growth attributes at W 1 F 3 was due to higher accumulation of GDD, PTU and HTU ( Table 2). The increased application of nutrients increases the uptake of nutrients by plants in winter maize which might be due congenial nutrient environment in soil and availability higher nutrients in rhizospere 49,52 .

Nutrients use efficiency (NUE) as influenced by planting windows
Nutrients use efficiency (NUE) shows the ability of crops to take up and utilize nutrients for maximum yields. NUE depends on the plant's ability to take up nutrients efficiently from the soil, but also depends on internal transport, storage and remobilization of nutrients. NUE of applied fertilizers is very low due to many reasons like surface runoff, leaching, volatilization, denitrification and fixation in the soil. The increased yield levels show the higher nutrient use efficiency. The better planting date will provide the congenial environment to plants to uptake more nutrients so that productivity of crops is increased. in transplanted rice crop.

Nutrient use efficiency (NUE) as influenced by fertility levels
Significantly higher AE N , AE P and AE K were recorded with application of 100 % RDF (Table 4). On the contrary lower agronomic efficiency for nutrients was recorded with higher fertility levels. For nitrogen, similar results were noticed by Vanlauwe et al. 55 in maize based system and according to them higher agronomic efficiency was recorded in lower nitrogen level. The similar results were also obtained by Caviglia et al. 56 who concluded higher agronomic efficiency in lower fertilizer level in both early and late sown maize. Similarly higher PE N , PE P and PE K were recorded with application of 100 % RDF and lower physiological efficiency was recorded with higher fertility levels (Table   4). Similarly, the higher RE N , RE P and RE K were obtained with application of 100 % RDF, whereas lower recovery efficiency was observed in higher fertility levels ( Table 4). Lesser the application of fertilizer higher will be the nutrient use efficiency 57,58 . This result is also conformity with the findings of Choudhary et al. 59 and they concluded that yield increase was decreased with each increased level of nitrogen application. The highest agronomic nitrogen use efficiency was recorded with 60 kg N/ha. N level of 180 kg/ha recorded the least. Yield increase due to per unit increase in uptake of N was decreased with increased levels of N application. The highest NUE always occurs at the lower parts of the yield response curve, where fertilizer inputs are the lowest. The effectiveness of fertilizers in increasing crop yields and optimizing farmer profitability should not be sacrificed for the sake of efficiency alone. There must be balance between optimum NUE and optimal crop productivity 60 .
Increased levels of fertilizer tend to lower the productive efficiency. week of November along with application of 100 % RDF ( Table 4). The higher agronomic efficiency in October 1 st week planting along with 100 % RDF was due to higher grain yield in early planting and lower fertility level which increased the efficiency. The recovery efficiency was also higher in October 1 st week planting which was due to higher applied nutrient uptake. The higher physiological efficiency was recorded during 1 st week of November which might be due to more capacity of plant to increase yield with per unit nutrient uptake. Lesser the application of fertilizer, higher will be the nutrient use efficiency 53,58,[65][66][67][68] .

Energetics as influenced by planting windows
In agriculture development, the energy audit of various resources plays a key role in resource management. Under the changing global climatic conditions and increasingly growing energy demands necessitate the development of a production system which utilizes less energy and produces more energy as output. The energetics was calculated per hectare and then these input data were multiplied with conversion factor of its energy equivalent. The energy indices were determined by using standard equation 30 .
The total input energy was lower for early planting windows due to lower irrigation requirement 71 3a). The higher energy use efficiency in early sown crop compared to late planting was due to higher grain yield and output of energy. Energy productivity was also higher from crop sown during 1 st week of October and was on par with planting during 2 nd week of October. Lower energy productivity was observed in 1 st week of November planting (Fig. 3a). Higher energy productivity was directly correlated with higher productivity. The specific energy was higher in 1 st week of November planting and lower specific energy was recorded in 1 st week of October planting (Fig. 3a). The higher specific energy in delayed planting was due to higher energy requirement to produce unit yield. The same results were observed by Puniya et al. 72 . The energy use efficiency (EUE) was significantly positively correlated with net energy return, energy productivity, energy intensity, energy output, helio-thermal use efficiency, heat use efficiency and significant negatively correlated with specific energy and helio-thermal units 71,72 .

Energetics as influenced by fertility levels
According to many researchers the inputs such as fuel, electricity, machinery, seed, fertilizer and chemical take significant share of the energy supplies to the production system in modern agriculture. Foremost important among them is careful management of fertilizers, because on the one hand, in many cases it alone share more than 50 per cent of total input energy used in a system and the other, it is the most imperative growth factor for proper growth and development of plants 11 . It was observed that, the fertilizers had the highest rate of energy equivalency of all the inputs used in maize production at 51.5 per cent 12 .
The total energy input in 200 % RDF was higher than other fertility levels due higher rate of application. Aakash et al. 9 reported that fertilizer management is very essential since it utilized almost 70% of total input energy used in maize production. Application of 200 % RDF recorded higher total output energy. Lower total output of energy was recorded with application of 100 % RDF due lower grain yield. Significantly higher grain and stover yield in higher fertility levels increased the total output energy. Hence, the net energy was higher in 200 % RDF and lower net energy was recorded with application of 100 % RDF. While, the energy use efficiency and energy productivity were higher in 100 % RDF (Fig. 3b). The higher energy use efficiency was due to higher ratio of output to input energy. Similarly, higher energy productivity was due to higher ratio of yield to input energy. The specific energy was higher with application 200 % RDF (Fig. 3b). This was due to higher energy requirement to produce unit yield in 200 % RDF [73][74][75][76] . The findings of Khokhar et al. 63 are similar to above results and they concluded higher input energy, output energy and energy balance in higher fertility levels and higher energy use efficiency and energy productivity in lower fertility levels in both maize and wheat crop.
Singh et al. 60 reported similar results and they reported higher output energy and net energy return in site specific nutrient management compared to farmer practice and RDF due to higher yield levels in precision nutrient management practices. Choudhary et al. 59 , Biswasi et al. 77 , Jayadeva and Prabhakar shetty 78 also found that higher input energy, output energy and net energy in higher fertility levels compared to lower fertility levels.

Interaction effect of planting windows and fertility levels on energetics
Interaction of planting windows and fertility levels plays an important role in energy flow in winter maize. Relatively higher input energy was recorded in 1 st week of November planting along with 200 % RDF. Planting during 1 st week of October along with application 200 % RDF (W 1 F 3 ) (Fig.3c) recorded higher total output energy compared to other treatment combinations.
The higher output energy was due to higher yield levels in W 1 F 3 . Higher net energy was recorded with planting during 1 st week of October along with application of 200 % RDF and it was found on par with early planting during 2 nd week of October and 1 st week of October along with application of either 200 % RDF or 150 % RDF. This was because there was higher input energy use which increased the grain and stover yield resulting in increased the total output energy and net energy, whereas higher energy use efficiency was recorded with planting during 1 st week of October along with application of 100 % RDF and was found on par with planting during 2 nd week of October along with application of 100 % RDF, planting during 3 rd week of October along with application of 100 % RDF (Fig. 3c). This was because the higher ratio of output to input energy. Similarly higher energy productivity was recorded with planting during 1 st week of October along with application of 100 % RDF and it was on par with planting during 2 nd week of October along with application of 100 % RDF, planting during 3 rd week of October along with application of 100 % RDF (Fig. 3c). Higher energy productivity was due to higher ratio of grain yield to energy input. Higher specific energy was recorded with planting during 1 st week of November along with application of 200 % RDF and was found on par with planting during 4 th week of October along with application of 200 % RDF (Fig. 3c). This was because in this treatment combination there was a higher requirement of energy to produce unit yield 72,73,79 .

Bio-economics
Significantly higher gross return, net return and B-C ratio was recorded with planting during 1 st week of October and it was on par with planting during 2 nd week of October. The higher gross return and net return were due to higher grain yield and stover yield in these two planting windows, whereas significantly lower gross return, net return and B-C ratio recorded with planting at 1 st week of November was due to lower productivity 46 . Among the fertility levels, significantly higher gross return and net return was recorded with application of 200 % RDF and was on par with application of 150 % RDF due to higher grain and stover yield in these two fertility levels, whereas significantly lower gross return and net return was recorded with application of 100 % RDF due to its lower grain and stover yield. There is no significant difference with respect to B-C ratio 69 .
Interaction effect showed that significantly higher gross return and net The higher gross return and net return in these interactions were due to higher grain and stover yield, whereas significantly lower gross return and net return were recorded with planting during 1 st week of November along with application of 100 % RDF was due to its lower productivity of crop 70 .

Conclusion
Planting of maize in winter season is more suitable than rainy season by looking at crop growth and productivity. The best planting windows to obtain higher productivity, NUE, energy use efficiency, energy productivity, net return and B-C ratio were 1 st and 2 nd week October. Among fertility levels, application of 200 % and 150 % RDF showed higher productivity. Whereas, higher NUE, energy use efficiency and energy productivity was recorded with 100 % RDF.