GROWTH RESPONSE TO SPRING MAIZE WITH DIFFERENT ZINC SOURCES

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Micro-nutrients deficiencies prevail in low and lime-amended high fertility soils are commonly present throughout the world.. Keeping this in view, a field study was conducted to evaluate the effectiveness of different sources of Zn i.e. ZnSO4.7H2O, ZnO2, Zn-EDTA and Zn-fulvate containing 22, 67.1, 14 and 8.3% Zn respectively on growth characters, mineral contents and yield of three hybrid maize (FH-421, FH-810 and M-919). The results of study revealed that yield and yield contributing parameters of maize plants were significantly improved under the application of Zn as compared to untreated plants. Maximum increase in biological yield, 1000-grain weight and grain yield was recorded up to 16.2, 7.1 and 23.2% in response to Zn-fulvate as compared to control respectively. It is concluded that grain yield of maize can be improved by applying Zn as Zn-fulvate @ 12 kg ha-1 in the agro-ecological conditions of Faisalabad, Pakistan.

INTRODUCTION

The growth and yield response of a plant is tested by the availability of some particular mineral nutrients that are tremendously essential for the metabolic activity and completion of life cycle (Marshner, 1995). Although, the application of essential nutrients to plants in the form of chemical fertilizers is necessary for sustainable agriculture system. While, Zn is an essential micronutrient for plant growth and is taken up by the plant roots in the form of Zn2+. It is involved in different metabolic activities, influences the activities of hydrogenase and stabilization of ribosomal fractions and auxin metabolism (Tisdale et al., 1984). Because of the Zn deficiency plants exhibit poor growth, interveinal chlorosis and necrosis of lower leaves (Throne, 1957).

Maize is an important cereal crop of the world. Its hybrids are fast growing and high yielding which therefore, require more nutrients as compared to indigenous varieties. While Zn deficiency in maize, coffee and citrus, which are considered to be highly responsive to Zn fertilization. Different species have different requirement of Zn. Differential cultivars responses grown under low soil Zn concentrations have been reported in maize, millet, sorghum, rice and wheat (Rashid and Ryan, 2004; Wissuwa et al., 2006).

Zn deficiency is common in cereals grown on alkaline calcareous soils due to this, a large population of the world also lacks adequate Zn nutrition (Maqsood et al., 2009). Likewise, Bhutta et al. (1999) documented that Zn deficiency in Pakistan in children less than five years of age and women of reproductive age. In Pakistan, a national nutrition survey exhibited Zn deficiency 37% of children and 41% in mothers (Anonymous, 2004).

Low soil Zn is attributed to a number of soil and abiotic factors including low soil organic matter, high soil pH, calcareousness, water logging and arid environment (Tandon, 1995). Generally Pakistani soils are alkaline in reaction and calcareous in nature. These types of soils usually contain lower amounts of available Zn therefore, soil application with Zn as ZnSO4.7H2O is widely recommended but its use as a soil additive is not a common practice of farmers. Less than 5% of Pakistani farmers use zinc fertilizer (FAO, 2004b).

Different nutrients may interact with Zn by affecting the availability of each other from soils environment as well as their status in the plant during growth process or uptake, distribution and utilization. These interactions may decrease or promote plant growth as a response to Zn (Longragan and Webb, 1993). Similarly, Yilmaz et al. (1997) concluded that over use of phosphatic fertilizers resulted in lower levels of Zn in cereal grain and human diets. Rathore et al. (1974) studied that increasing either element (Zn or Mn) minimize the toxic effect of others nutrients and implied a mutual antagonistic effect on Zn uptake.

It is obvious that use of micro-nutrients including Zn is an imperative factor for hybrid maize crop cultivation and these essential nutrients should be used for increasing soil fertility and to boost up crop yield. The present research was undertaken to study the effect of different sources of Zn on growth and yield of hybrid maize under natural conditions.

MATERIALS AND METHODS

A field study was carried out to test the effectiveness of different Zn sources on growth and yield of three maize hybrids at the Agronomic Research Area, University of Agriculture Faisalabad, Pakistan.. Maize hybrids FH-421, FH-810 and M-919 were sown by manually dibbling method on 75cm apart from rows and plot size was 3.6m x 6m. Plant to plant distance of 25cm was maintained by thinning. Recommended doses of NPK @ 250-125-125 kg ha-1 were applied in the form of urea, single super phosphate (SSP) and sulfate of potash (SOP) according to the treatments. Treatments were replicated three times using Randomized Complete Block Design (RCBD). All phosphatic and potashic fertilizers were applied as basal dose at the time of seedbed preparation while N was applied in splits. Canal water was used for irrigation. Field with sandy clay loam soil having physico-chemical properties: pH 7.7; electrical conductivity (ECe) 3.3 dS m-1; organic matter 0.69 %; total nitrogen, 0.04 %; available phosphorus 8.9 mg kg-1 and extractable potassium 131 mg kg-1.

The experiment was conducted with following treatments: Control (untreated); ZnSO4.7H2O, ZnO2, Zn-EDTA and Zinc fulvate containing 22, 67.1, 14 and 8.3 % Zn respectively. All the Zn sources were applied before first irrigation as foliar spray according to their recommended dose. All other agronomic practices were same for all the treatments. Data regarding growth and yield contributing parameters were recorded. Data were subjected to statistical analysis by using standard procedures (Steel et al., 1997). The differences among the treatment means were compared by applying the Duncan's multiple range tests (DMR) (Duncan, 1955).

RESULTS

Results regarding biological yield are presented in Table 1. In general, it was observed that Zn amended soil showed effective increase in biological yield as compared to respective control. The maximum (16.2%) biological yield was obtained in response to ZnSO4.7H2O followed by Zn-fulvate as compared to control. Among the varieties, M-919 showed highest potential to improve biological yield in comparison with FH-421 and FH-810. But there was observed no significant effect on the biological yield of the varieties by the application of Zn treatments.

Grain yield is the function of an interaction among various yield components and crop management practices. Data concerning grain yield had shown in Table 1 that all the Zn amended treatments had shown positively increase in grain yield as compared to control while treatments ZnSO4.7H2O, Zn-EDAT and Zn-fulvate were statistically at par. The maximum (23 %) increase in grain yield was obtained due to application Zn-fulvate. Varieties had still no effect on the grain yield by the application of Zn.

Individual comparison of Zn amended treatments are given in Table 1 showed that maximum increase in 1000-grain weight was up to 7.1 % as a result of Zn-fulvate which was showed statistically at par difference in 1000-grain weight in comparison with rest of Zn amended treatments. While in case of varieties maximum 1000-grain weight was recorded by M-919 followed by FH-421 and FH-810. These indicate that the varieties had no significant effect on the application of Zn treatments.

Data regarding number of grains per cob revealed that treatments containing Zn showed significant effect on the number of grains per cob as compared with respective control (Table 2). The maximum increase in number of grains per cob was recorded up to 6.5 % in response to ZnO2 which was statistically at par with rest of the Zn amended treatments. The varieties had no significant effect on number of grains per cob.

Number of grain line per cob is an important yield determining factor in maize. It directly affects the number of grain lines per cob (Table 2). Maximum numbers of grain lines per cob were recorded due to application ZnSO4.7H2O as compared with control while this treatment was statistically at par with rest of the Zn treatments. Varieties were shown non significant effects on the number of grains lines per cob.

It is clear from results that Zn treatments had significant effect on the cob diameter. Maximum (8.7 %) increase in cob diameter was observed by the application of ZnO2 as compared to control while this treatment was statistically similar to other Zn amended treatments (Table 2). The minimum cob diameter was observed in case untreated control. Varieties had also shown no significant effect on the cob diameter. Plant height reflects the vegetative growth behavior of crop plants in response to applied inputs. Results regarding plant height revealed that Zn application showed significant effect on plant height as compared with untreated control (Table 3). Maximum plant height was recorded by application ZnO2 that was 3.5 % more than untreated control. Varieties showed no significance effect to Zn application.

Data about number of plants per plot showed that there is no significant effect of Zn application on plant population. Moreover, comparison of varieties had also shown non significant effect on plant population per plot. FH-810 produced maximum number of plants per plot which is statistically at par with FH-421 and M-919 varieties. But M-919 produced least number of plants per plot.

Harvest index is the ratio of economical and biological yield expressed in percentage. Data about harvest index revealed that harvest index (%) was significantly affected by Zn treatments. Significantly the highest harvest index (7.9%) was obtained where Zn-EDTA was applied as compared to control but it was statistically at par with other Zn amended treatments. It is evident from the results that all of the three varieties had no significant effect on harvest index.

DISCUSSION

Micronutrients are very important for plant health and add greatly to yield, which is the main concern for much of the agricultural industry. One of the most important micronutrients is Zn. Zinc deficient soil can be found throughout the world and are normally associated with low soil organic matter and a soil pH higher than 7. The results of our study showed that effect of different sources of Zn application on plant height was at par with each other but all sources of Zn showed give significant effect over control while varietals effect were also non significant with each other. These results are in line with those of Sanzo et al. (1994). They reported that there were no differences in plant height of rice with the application of Zn. While application of Zn sources was showed significant effect on biological yield that was in line with the findings of Furlani et al. (2005) who reported that Zn application enhanced biological yield significantly in comparison with untreated control.

In this study, it was observed that grain yield of maize increased significantly as compared with respective control. However, these findings are confirmatory to those of Alloway (2004). Similar results are also documented by Abunyewa and Mercer-Quarshie (2004); Himaytullah and Qasim (1998) who reported that grain yield of maize was increased by the application of trace element but these results were opposite to those of Maji and Bandyopadyay (1990). They reported that soil and foliar application of micronutrients had no effect on grain yield of rice. No significant difference of Zn sources was reported by Sajwan and Lindsay (1988). Similar effects of Zn sources were observed on 1000-grain weight while varietial effects were found non-significant with each other. These results are also confirmatory as the finding of Himaytullah and Qasim (1998); Tariq et al. (2002) who had recorded that yield and yield components of maize were significantly increased with Zn application.

In case of number of cobs per plant and number of plants per plot due to application of different sources of Zn were observed at par to each other while showed significant effect as compared to untreated control. Although our results were contrary to the findings of Himaytullah and Qasim (1998) who reported that number of cobs per plant were increased significantly by the trace element in the presence of N, P and K. Effect of Zn application on cob diameter as well as on number of grains per cob was highly significant among each other as well as respective control. The results of our study were supporting to the findings of Himaytullah and Qasim (1998) who studied that use of Zn significantly influenced the number of grains per cob. The same results were also reported by Shaaban (2001).

It is concluded from the study that maize grain yield under agro-ecological conditions of Faisalabad, Pakistan could be enhanced comparatively by application of Zn as Zn-fulvate than other sources of Zn.

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