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To study the interaction effect of Fe×Mn on yield, chemical composition and nutrient uptake at various cuttings of spinach plants and grain, straw at maturity

A pot experiment was conducted at pot culture yard in Department of Agricultural Chemistry and Soil Science, R.B.S. College Bichpuri, Agra (UP). To study the interaction effect of (Fe × Mn) on yields, chemical composition of plants at different growth stages and uptake of nutrients by grain and the straw at maturity by spinach crop. Four levels (0, 5, 10, 20 ppm) of each iron and manganese were evaluated in factorial design with three replications. The results indicated that the interaction of effect of (Fe × Mn) on yields was found to be significant. The maximum values (19.5, 49.0 mg/pot) of green foliage and dry matter (2.4, 5.6 mg/pot) were noted under 10 ppm Fe + 10 ppm manganese dose. The highest dose (20 ppm iron and 20 ppm manganese) reduce the yields upto minimum levels. Nutrient composition of spinach plants grain and straw in respect of N, P, Fe, Mn content was consistently increase up to (10 ppm) dose of iron and manganese level. Thereafter, a deduction was noted with higher dose (20 ppm) iron and manganese. Similar tend was noted in case of nutrients uptake by spinach plants. It is concluded from the results that (Fe × Mn) with dose of 10 ppm was found to significantly superior over rest of the combinations. Investigations also revealed that Fe and Mn has antagonistic relation in respect their content and uptake in all the growth stages of spinach plants.


Introduction
In order to boost up crop production per unit area per unit time, increasing emphasis is being laid on cultivation of high yielding varieties of crops intensive cropping heavy fertilization and modern techniques of cultivation. In this context, importance of micronutrients can hardly be over emphasized as in many areas their supply in soil may become a limiting factor in obtaining maximum levels of crop yields. In several parts of the country micronutrients disorders have been recognised as major cause of crop failure and poor productivity (Takkar and Randhawa, 1978) [11] . Substantial improvement in the performance of crop have been reported as a result of micronutrient supplement of soil for crop from different parts of country (Kanwar andRandhawa, 1974, Katyal, 1986) [5,6] . Thus the need for knowledge of micronutrients status of soil assumes still greater importance in view of increased hectare yields. Among various micronutrients, manganese is especially important owing to its typical and complex behaviour in soils besides, its vital and indispensable role in plant growth. Manganese functions in the activation of numerous enzymes concerned with carbohydrate metabolism, phosphorylation reactions and the citric acid cycle and with other metal in the activation of such enzymes as arginase, cystein, desulphydnase, deoxyribonuclease and yeast phosphatase. Apparently it is specific activator of the enzymes prolidase and glutomyl transferase. Antagonist relationship between Fe and Mn has been reported in soils and plants (Pathak et al., 1979) and likewise they influence yield of crop differently. Basen and Saxena (1970) [2] and Jain (1973) obtained increased rice yield by the application of Fe and Mn. Ratios of Fe and Mn either in soil and plant have no significant impact on crop yield, only their addition in optimum concentration is of great significance (Agarwala and Associates, 1964) [1] .
Such information available in this respect, so far is rather meagre in soils of Agra. Hence the study is being undertaken with a view to study the Fe and Mn interaction of yield, their content and uptake by Spinach crop.

Materials and Methods
A pot culture experiment was carried out using spinach crop in pot culture yard in the department of soil science and agriculture chemistry RBS College Bichpuri, Agra. The experimental soil was collected from research farm of RBS college the experimental soil was sandy loam in texture alkaline on reaction (pH 8.0) with organic carbon content 3.4 kg per hectare, available N 160 kg per hectare, available phosphorus 8.4 kg per hectare, available potassium 115 kg per hectare, total Fe extracted with HClO4 (1.8%), available Fe-DTPA (4.5 ppm), total Mn (350 ppm), determined by methods of Willard and Greathouse (1917) [12] , available Mn (7.0ppm) extracted with DPTA and determined colorimetrically by Willard and Greathouse (1917) [12] . The experiment comprising four levels (0, 5, 10, 20 ppm) of iron and four levels (0, 5, 10, 20 ppm) of manganese was conducted in a factorial randomised block design with three replications in 48 pots. Forty eight earthen pots of similar size and shape were selected clean and lined with polythene sheets after mixing the soil lot thoroughly 6kg of soil was filled in each pot iron manganese were applied through ferrous sulphate and manganese sulphate respectively. The Basal doses of nitrogen Phosphorus and potassium were applied through urea single super phosphate and muriate of potash respectively at the time of sowing. The crop was raised with recommended agronomic practices. First cutting of spinach was done after 15 days of sowing followed by second cutting 20 days after first cutting. The yield data in regard to green foliage and dry matter were recorded at first and second cuttings. The samples were analysed for nitrogen content by modified Kjeldahl method (Jakson 1973). Phosphorus in diacid (HNO3: HClO4) digest were determined by vanadomolybdate yellow colour method and flame photometre respectively. Iron and Mn in di-acid digest were determined on atomic absorption spectrophotometer uptake of nutrients was calculated by multiplying nutrient content with their respective dry matter yield.

Results and Discussion Yield
The interaction effect of Mn×Fe on yields was found to be significant. An analysis of data given in table 1 reveals that the green foliage and dry matter yields at both cuttings and grains and straw yields of spinach at maturity were increased consistently with applied manganese under lower levels of iron. The yields of spinach were reduced under 20 ppm Mn in the absence and presence of iron. The minimum yields of spinach at different stages of growth were recorded under 20 ppm Mn and 20 ppm Fe treatment. The maximum green foliage and dry matter yields at both cuttings and grains and straw yields at maturity were noted under 10 ppm Fe and 10 ppm Mn treatment. Similar results were reported by Swarup and Mishra (1972) [10] .  Singh and Singh (1975) [9] also reported similar findings. It is evident from the data presented in table-2

Chemical composition of nutrients at maturity
It is evident from data given in table-3 [7,8] that wheat crop responded to lower levels of iron and manganese applications. The application of iron reduced Mn content and vice versa.

Nutrients uptake
The interaction effect of Fe×Mn as reflected from the data given in table 4 [7,8] .