Maize, being a C
4 plant and versatile in nature adapts to various agro-climatic conditions. Maize attains third position after rice and wheat in India. Owing to its high yield potential among cereals, it is considered as Queen of cereals. It is consumed by humans as food and also serves as feed to animals, poultry. The maize productivity of India is (2583 kg ha
-1) which is very lower while compared with other countries (5160 kg ha
-1) due to improper nutrient management practices. Zinc an essential micronutrient is found deficient in soils due to lack of organic sources of nutrient supplement and use of high analysis fertilizers. The deficiency of zinc in soils has increased from 44% to 48% and further increase to 63% is expected by 2025 in India
Preetha and Stalin (2014). Zinc is essential for maintaining structural and functional integrity of 2,800 proteins, also contributes to biosynthesis of protein and serves as a key defense factor for detoxification of oxygen-free radicals that are highly toxic (
Cakmak 2000,
Broadley et al., 2007). The plant physiologists have well documented the profound influence of zinc in plants on basic plant life processes, like nitrogen uptake as well as its metabolism, protein quality, role in photosynthetic activity, synthesis of chlorophyll and carbon anhydrase activity, resistance to biotic and abiotic stresses and protection from oxidative damage (
Alloway, 2004;
Cakmak, 2008). Maize is a zinc responsive crop and aids in yield improvement leading to substantial increase in maximum net returns to farmers. The production of growth hormone indole acetic acid is mainly by zinc that results in higher auxin content leading to increased growth and yield of maize
Fajudar et al., (2014). Application of zinc has shown positive trend with regard to growth parameters, yield parameters, nutrient uptake, yield, quality and economics of maize by different researchers has been cited in the present review paper.
Effect of zinc levels on growth parameters of maize
Goos et al., (2000) stated that increasing levels of zinc application resulted in higher dry matter production in maize. Application of Zn with increasing levels of 30 kg
ha-1 registered significant increase in dry-matter accumulation in maize
Arya and Singh (2001).
Adiloglu (2007) concluded that application of 10 kg Zn ha
-1 gave significant increase in dry matter production of maize from his study. Leaf area index was significantly higher with application of zinc at increasing levels up to 8 kg ha
-1 over control in maize
Sarwar et al., (2012).
Mahdi et al., (2012) observed a significant increase in plant height and leaf area index with application of zinc at 10 kg ha
-1 than lower levels in fodder maize from his study.
Raskar et al., (2012) concluded that plant height was significantly increased with application of 5 kg Zn ha
-1 than no application in maize from his experiment.
Meena et al., (2013) found that plant height and dry matter production of maize was significantly higher with application of 5 kg ha
-1 and remained statistically on par with 7.5 kg ha
-1 of zinc application from his study.
Kumar et al., (2014) concluded that increasing levels of zinc application to 10 kg ha
-1 increased the growth parameters like number of green leaves plant
-1, plant height, stem girth, dry matter production plant
-1 and crop growth rate than lower levels and control from his study in maize crop. Foliar application of Zn and B gave a significant increase in dry weight and crop growth rate as result from increased chlorophyll production and photosynthesis in maize
Tariq et al., (2014). Zinc application had significant increase in height of plant and other growth attributes which might be due to stimulatory effect of zinc on most of the physiological as well as metabolic processes of plant
Panneerselvam and Stalin (2014). Root length, dry weight of roots, root volume were significantly improved with application of zinc at 10 kg ha
-1 in maize over control
Kumar et al., (2015). Azab (2015) revealed that combined application of NPK fertilizer and Zn (2%) gave significant increase in plant height, leaf area, fresh weight and also the dry weight of corn than no application of zinc. Application of 0.2% zinc significantly increased the individual leaf area, plant height and leaf area index
Amanullah et al., (2016). Wasaya et al., (2017) stated that application of zinc and boron gave significant increase in growth parameters such as plant height and leaf area index in maize from his study.
Marngar and Dawson (2017) concluded that application of zinc at 15 kg ha
-1 gave significant increase in plant height at (148.23 cm), no. of leaves plant
-1 (13.67), dry weight (23.10 g plant
-1) than no application from his study. Growth parameters such as plant height, dry weight of plant was higher at early and harvesting stages with application of 150 kg N ha
-1 + 25 kg Zn ha
-1 which was statistically significant than control treatment in maize
Reddy et al., (2019).
Effect of zinc levels on yield parameters and yield of maize
Osiname et al., (1973) found that application of zinc upto 1 to 2 kg ha
-1 had significantly increases the grain yield in maize in the range of 814 -1747 kg ha
-1.
Shukla and Prasad (1974) stated that zinc application significantly increases the maize yield.
Rehman and Barnard (1988) reported zinc application at 5 kg ha
-1 gave maximum yield over no application in maize.
Arya and Singh (2000) found that grain yield and stover yield was significantly increased in maize with application of zinc at increasing levels up to 30 kg ha
-1.
Shaaban (2001) stated that zinc application significantly increased the number of grains
cob-1 in maize.
Dwivedi et al., (2002) stated that maize yield was significantly higher to the tune 19% with application of zinc at 5 kg ha
-1 as compared to control treatment.
Abunyewa and Quarshie (2004) observed a significant increase in grain yield from 84-108% with zinc application at 5 kg ha
-1 over control and was statistically on par with 10 kg ha
-1. Shanmugasundaram and Savitri (2005) reported significant increase in grain yield with application of 37.5 kg ha
-1 zinc than12.5 kg ZnSO
4 ha
-1 in maize from his study.
Kassab (2005) found that application of zinc resulted in significant increase in number of grains cob
-1 in maize. Test weight, cob yield and grain yield of maize was significantly higher with application of 5 kg Zn ha
-1 than no application
Kakar et al., (2006). Harris et al., (2007) observed a significant increase in grain yield of maize seed primed with 1% Zn.
Ghodpage et al., (2008) concluded that grain yield and fodder yield significantly increased with 20 kg ha
-1 of zinc than lower levels and control from his experiment.
Hossain et al., (2008) concluded that increasing zinc levels up to 4 kg ha
-1 gave maximum grain yield (10.6 t ha
-1) than 2 kg (10.1 t ha
-1) and control (7.4 t ha
-1) in maize crop from his experimental result.
Zeb and Arif, (2008) documented that application of zinc gave significant increase number of grains cob
-1 in maize. Ziaeryan and Rajaie (2009) observed a significant increase in test weight of maize grain with zinc application.
Potarzycki and Grzebisz, (2009) reported that zinc foliar spray gave significant increase in grain yield with the range of 1.0 to 1.5 kg ha
-1 in maize crop.
Paramasivan et al., (2010) reported a significant increase in grain yield (7908 kg ha
-1) with application of 10 kg Zn ha
-1.
Sachin et al., (2011) found that increasing zinc application up to 50 kg ha
-1 significantly increased grain yield of maize from his study. Significant increase in test weight (46 g), number of grains spike (52), grain yield(2950 kg ha
-1), straw yield (6074 kg ha
-1) and biological yield (8999 kg ha
-1) in wheat with 0.5% of zinc as foliar spray
Gul et al., (2011). Raskar et al., (2012) revealed that yield parameters
viz., cob length, seed index, number of grain rows cob
-1, grain yield cob
-1 and shelling percentage were significantly higher with application of 5 kg Zn ha
-1 than control treatment. The grain yield and stover yield were increased in the tune of 10.21% and 7.76% compared to control treatment. Significant increase in green fodder yield was noticed with application of zinc at 10 kg ha
-1 Mahdi et al., (2012). Meena et al., (2013) documented that grain yield was significantly higher with application of zinc at 5 kg ha
-1 than 2.5 kg ha
-1 and remained statistically at par with 7.5 kg ha
-1 in maize. Application of 27 kg ha
-1 of zinc significantly increased the number of grains cob, test weight and grain yield of maize
Asif et al., (2013). Kumar and Bohra (2014) found that application of 10 kg Zn ha
-1 gave maximum baby cob yield (9.24 t ha
-1), baby corn (2.1 t ha
-1) as well as green fodder yield (30.49 t ha
-1) over control treatment.
Mohsin et al., (2014) revealed that combined application of zinc as 2% seed priming and 2% foliar spray in maize hybrid significantly gave higher cob length, cob diameter, test weight, grain yield and harvest index over control.
Manzeke et al., (2014) registered an significant increase in grain yield by 29% by application of 25 kg ha
-1 than no application in maize crop.
Tariq et al., (2014) found that application of zinc and boron as foliar spray increased the grain yield of maize.
Eteng et al., (2014) stated that application of zinc at 8 kg ha
-1 gave higher yield in maize crop than control.
Faujdar et al., (2014) documented an significant increase in grain yield and stover yield to a tune of 17.6 and 16.2 with application of 5 kg ha
-1 of zinc compared to control treatment. Zinc application has significant effect in determining the yield potential of maize and gave higher number of grains cob
-1 Potarzycki
et_al(2015).
Kumar et al., (2015) documented that baby corn yield was increased with application of 10 kg Zn ha
-1 to the tune of 12.8% than control treatment and also gave maximum green fodder yield which was 10.3%, higher over control.
Ehsanullah et al., (2015) reported that application of zinc resulted in significant increase in number of grains cob in maize.
Ruffo et al., (2016) documented that application of zinc at 11 kg ha
-1 gave higher yield (11,530 kg ha
-1) than control treatment (10,540 kg ha
-1) in maize.
Wasaya et al., (2017) observed significant increase in yield parameters and yield of maize with application of zinc and boron from his study.
Kumar et al., (2017) concluded that zinc application at 10 kg ha
-1 gave a significant increase in yield parameters, grain yield and fodder yield of maize. Application of 25 kg Zn ha
-1 with 150 kg ha of nitrogen documented higher grain yield (37.03 q ha
-1) which was 27.02% higher than control treatment (10.65 q ha
-1).
Marngar and Dawson (2017) observed a significant increase in grain yield (7.9 t ha
-1) with application of zinc 15 kg ha
-1 over control treatment.
Kumar et al., (2018) documented significant increase in grain yield and stover yield of maize with application of zinc at 25 kg ha
-1 from his study.
Kumar et al., (2019) observed that grain yield and biological yield increased with application of 25 kg ha
-1 of zinc at the tune of 22.81% increase in first year and 4.10% in the second year over control in maize from his study. Maximum fodder yield (53.29 q ha
-1) was recorded with 150 kg N ha
-1 + 25 kg Zn ha
-1 which was 52% higher than control treatment (28.09 t ha
-1)
Reddy et al., (2019).
Effect of zinc levels on quality of maize
Increasing zinc application up to 30 kg ha
-1 had significant increase in protein yield of grains in maize crop
Arya and Singh (2000).
Tahir et al., (2009) stated that application of zinc significantly increased the quality parameters crude protein, soluble protein and protein yield of maize from his experiment.
Leach and Hameleers (2011) observed that starch content increased with zinc application in maize at harvest in maize.
Ghaffari et al., (2011) found that application of zinc at 2% through foliar spray significantly enhanced the quality parameter of maize. Crude protein content and protein yield in maize were statistically higher with application of 10 kg zinc ha
-1 than control treatment
Mahdi et al., (2012). Protein content was higher with application of zinc at 27 kg ha
-1 than control treatment in maize crop from his study
Asif et al., (2013). Mohsin et al., (2014) concluded that seed priming 2% and foliar spray 2% significantly increased the zinc content in maize grain from his investigation.
Manzeke et al., (2014) found that application of zinc enhanced the quality of maize grains and increased zinc concentration to 67% in grains.
Shivay and Prasad (2014) documented that zinc application at 5kg ha
-1 in soil in addition 1 kg foliar spray increased the crude protein content (10.3%) compared to control(9.0%) in corn. Increasing levels of zinc up to 10 kg ha
-1 gave significant improvement in crude protein content and fibre content compared to no application in baby corn
Kumar et al., (2015). Patil et al., (2017) registered that application of maize residue compost enriched with 15 kg ZnSO
4 gave a significant increase in quality parameters of maize
viz., crude protein content (12.67%), protein yield (760.14 kg ha
-1) and soluble protein in grain (5.39 mg kg
-1) from his study.
Kumar et al., (2017) reported that application of zinc at 10 kg ha
-1 increased the crude protein content of maize crop from his study.
Effect of zinc application on nutrient contents and their uptake
Arya and Singh (2000) documented that application of 30 kg ha of zinc gave significant increase in zinc uptake of grain and straw of maize than lower levels from his experiment. Application of zinc at 10 kg ha
-1 significantly increased the zinc uptake of maize
Dwivedi et al., (2002). Zinc content of maize grains increased with zinc application of 20 mg kg
-1 of soil
Adiloglu and Saglam (2005). Application of 9 kg Zn ha
-1 significantly increased the uptake and content of N, P, K, S and Zn in maize than lower levels from his experimental study
Jain and Dahama (2005).
Ghodpage et al., (2008) registered an significant increase in N, P and Zn content of maize with application of increasing levels of zinc 20 kg ha
-1. N and Zn content uptake was increased with application of 10 kg Zn ha
-1 in fodder maize Mahdi
et_al(2012).
Meena et al., (2013) reported that uptake of zinc in maize grain was significantly altered with increment of zinc application up to 7.5 kg Zn ha
-1.
Puga et al., (2013) reported that zinc application significantly increased the zinc content of maize seeds from his research study. Zinc content in maize grain was enhanced with foliar spray of 2% and seed priming 2%
Mohsin et al., (2014). Eteng et al., (2014) concluded that application of zinc at 8 kg ha
-1 gave maximum nutrient uptake in maize crop than other levels and control. Combined application of NPK inorganic fertilizers and zinc 1.5% enhances significantly the uptake of NPK and N, P, K, Cu, Fe, Mn and Zn content in maize grains than no application of zinc
Azab (2015).
Imran et al., (2013) found that seed priming of zinc resulted in significant increase in zinc content of maize seed (500%) from his study.
Faujdar et al., (2014) reported that application of zinc enhanced the nutrient uptake status of other macro and micronutrients with application of 5 kg zinc ha
-1 in maize crop from his investigation.
Ramanjineyulu et al., (2018) concluded that foliar application of 0.1 per cent ZnSO
4 had significant impact on effect of micronutrient uptake of maize crop.
Effect of zinc levels on economics of maize
Increasing levels of zinc upto 10 kg ha
-1 significantly gave higher net returns and benefit cost ratio in fodder maize from his study
Mahdi et al., (2012). Zinc application at 10 kg ha
-1 registered higher net returns and benefit cost ratio (2.10) which was higher than lower levels in fodder maize
Meena et al., (2013). Kumar and Bohra (2014) concluded that application of zinc at 10 kg ha
-1 gave maximum net profit (1,38,810 Rs.ha
-1) over control from his study. Application of zinc at the rate of 5 and 10 kg ha
-1 registered higher gross returns, maximum net returns and benefit cost ratio which were statistically on par but comparatively higher than no application
Kumar et al., (2015). Benefit cost ratio (3.32) was higher with application of 15 kg zinc ha
-1 compared to control in maize
Marngar and Dawson (2017).
Kumar et al., (2017) reported that application of 10 kg ha
-1 of zinc resulted in maximum monetary returns from his study in maize crop.
Wasaya et al., (2017) reported that application of zinc and boron as foliar spray gave higher benefit cost ratio (1.84) compared to control (1.26) in maize crop.
Humtsoe et al., (2018) registered that application of zinc at 25 kg ha
-1 in addition with boron foliar spray gave higher benefit:cost ratio of (2.17) compared to control treatment (0.88) from his study.
Kumar et al., (2018) observed the benefit cost ratio was higher with application of 25 kg zinc ha
-1 over control in both crops from his study on maize.
Reddy et al., (2019) reported that application of 25 kg ha
-1 of zinc along with 150 kg ha
-1 of nitrogen gave maximum net returns (Rs.59108.00 ha
-1) and the benefit cost ratio (1.63) which was higher than control treatment lowest net returns (Rs.2518.70 ha
-1) and the benefit cost ratio (0.08).