Influence of Iron and Arbuscular Mycorrhiza Inoculation on Growth and Yield of Hybrid Maize in Calcareous Soil

Field experiment was conducted at the

Maize (Zea mays L.) is the third most important cereal next to rice and wheat, in the world and in India.It is also known as "Queen of cereals".It has got immense potential and hence called a "Miracle crop".Maize is cultivated both in tropical and temperate regions.It is one of the world's leading crops cultivated over an area of about 157.1 million hectares with a production of about 770.0 million tonnes and productivity of 4.71 tonnes of grain ha - 1 .In India, maize was cultivated over an area of 8.26 million hectares with a production of 19.30 million tonnes and the average productivity is 2337 kg ha -1 in 2006.In Tamil Nadu, in 2005, maize was cultivated in an area of 0.20 million hectares with a production of 0.24 million tonnes and productivity of 1189 kg ha -1 (Crop Report, 2006-07).
Maize has high yield potential and responds greatly to nutrient application.Apart from major nutrients, despite being needed in small quantities, micronutrients are also essential for the overall performance and health of the maize crop.They include iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo) and boron (B).Among the micronutrients, Fe and Zn are more important to maize.
Iron deficiencies are found mainly on calcareous (high pH) soils which reduces iron uptake by plants causing iron chlorosis.Foliar applications of iron used for corn, sorghum have been more effective on hybrids/varieties relatively tolerant of iron chlorosis.
Mycorrhiza is an association or symbiosis between the roots of most land plants and many soil fungi that colonize the cortical tissue of roots during periods of active plant growth, from which both partners benefit; arbuscular mycorrhiza (AM) is the most common and universal mycorrhiza.Arbuscular mycorrhizal fungi are widespread and agronomically important plant symbiont and often stimulate plant uptake of nutrients such as P, Zn, Cu, and Fe in deficient soils (Liu et al., 2000).The micronutrient improvement in mycorrhizal plants is always associated with rhizosphere acidification (Dodd et al., 1987), more external mycelium in the soil (Jakobsen et al., 1992) and soil biochemical changes.
The AM isolates improve Fe acquisition in maize grown under severe Fe deficiency conditions.Improved host plant, root development, morphology and acquisition of P may have been involved in enhanced Fe acquisition by AM plants.Glomus mosseae inoculated corn plants display better growth responses than no mycorrhizal plants at relatively low iron concentration while at high concentrations there was no pronounced effects.High mycorrhizal colonization allows mycorrhizal plants to transport more nutrients beyond the rhizospheric zone.Iron concentrations and contents generally increased in AM plants grown on the alkaline soils.With these ideas in view, the present investigation was carried out to study the

Materials and Methods
A field experiment was conducted during Kharif 2010 at Tamil Nadu Agricultural University, Coimbatore.The experimental soil was sandy clay loam in texture having a pH of 7.58.The fertility status was low in available N (220.4Kg ha -1 ), medium in available P (13.1 Kg ha -1 ) and high in available K (457.5 Kg ha -1 ).The available Fe (DTPA-extractable) content was 2.24 ppm.The experiment was laid out in factorial randomized block design with three replications.
Hybrid maize (CO H(M)5) was used as test crop and it was sown by adopting a spacing of 60 x 25 cm.Seeds of maize hybrids under AM inoculation treatments were sown with vermiculite based mycorrhizal inoculum at a depth of 5 cm below the seeds.An uniform fertilizer schedule was followed at the rate of 150: 75: 75 Kg NPK ha -1 .Nitrogen was applied in three splits as 25: 50: 25 per cent as basal, at 25 and 45 days after sowing, respectively.The entire dose of phosphorus was applied basally.The potassium was applied in two equal split doses viz., basal and at 45 days after sowing.Iron was applied basally and as foliar spray of 0.5% FeSO4.Foliar spray was given twice at 35 and 45 days after sowing.During the course of investigation, plant height leaf area index, dry matter production and yield were recorded.The data collected were statistically scrutinized and results presented.

Plant height
Among the iron treatments, the tallest plants were recorded with application of 25 kg FeSO4 + 0.5% FeSO4 foliar spray and was comparable with 50 kg FeSO4 + 0.5% FeSO4 foliar spray (Table 1).This might be due to increased availability and uptake of iron which might have resulted in the increased uptake of N which in turn might have increased the plant height.Amanullah et al. (2007) in sorghum and Ramu and Reddy (2007) in maize hybrid reported that addition of iron enhanced the growth parameters.With regard to mycorrhiza, AM inoculation significantly increased plant height.This might be due to the formation of external mycelium around the roots by AMF fungi and that resulted in better uptake of nutrients.Similar result was obtained by Khaliq and Sanders (1997).

Leaf area index
Leaf area index estimated at 60 days showed that application of 25 kg FeSO4 + 0.5% FeSO4 foliar spray recorded the highest leaf area index (7.92)1).The increased leaf area index might be due to the production of more number of leaves per plant due to iron application.Amanullah et al. (2007) reported an increase in LAI of sorghum due to foliar spray of iron which might have caused fast and speedy entry of iron.AM inoculation significantly increased leaf area index, which might be due to the increase in the number of leaves and the leaf enlargement by virtue of better nutrient uptake.Similar results were reported by Ananthi (2010) in hybrid maize.

Drymatter production
The highest DMP was obtained under iron treatment 25 kg FeSO4 + 0.5% FeSO4 FS which was comparable with 50 kg FeSO4 + 0.5% FeSO4 FS, 50 kg FeSO4 alone and 0.5% FeSO4 FS alone (Table 1).It might be due to the application of Fe which accentuated the availability in the soil favourably which contributed towards the better uptake and nullifying the deficiency that might have helped in increasing dry matter accumulation.The results are in conformity with the findings of Amanullah et al. (2007).Inoculation of mycorrhiza significantly increased dry matter at 60 and 90 days after sowing.The higher uptake of nutrients due to the formation of external mycelium around the roots by AM fungi might be the reason for the higher DMP.Similar results were reported by Ananthi (2010) and Wang et al. (2006) in maize.

Grain yield
Application of 50 kg FeSO4 + 0.5% FeSO4 FS recorded the highest grain yield of 5752 kg ha -1 followed by 25 kg FeSO4 + 0.5% FeSO4 FS and 50 kg FeSO4 and both were comparable with each other (Table 2).This increase in yield was due to effective utilization of applied nutrients.The positive and significant improvement in LAI and DMP noticed at different stages, increased yield attributes and nutrient uptake.Both soil and foliar application of FeSO4 would have resulted in enhanced grain yield.The results are in conformity with the findings of