Impact of iron and zinc agronomic biofortification on yield, concentration and uptake of nutrients in wheat as affected by iron and zinc solubilizing microbial inoculants

\Field experiment was conducted to improve Fe and Zn concentration and yield of wheat in response to varying Fe and Zn solubilizers and fertilizer application rates. The field experiment was carried out during rabi season of 2021-22 at research farm Department of Soil Science and Agricultural Chemistry, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. Experiment consists of thirty six treatment combinations which includes four iron and zinc solubilizing cultures (Control, Pseudomona striata, Pseudomona fluorescens, and Bacillus megaterium), three levels of iron sulphate (0, 20 and 40 kg FeSO4 ha-1) and three levels of zinc sulphate (0, 20 and 40 kg ZnSO4 ha-1) in factorial randomized block design. The results emerged out found significant effect of iron and zinc solubilizing microbial inoculants particularly Pseudomona striata and in levels of iron sulphate and zinc sulphate upto40 kg ha-1on yield and concentration of iron and zinc. Significant increase in grain yield was noted with the application of Pseudomona striata (2968 kg ha-1) over control. Higher grain yield found with application of 40 kg FeSO4 ha-1 (2975 kg ha-1) and 40 kg ZnSO4 ha-1 (2971 kg ha-1). Similarly, maximum straw yield noted with application of Pseudomona striata (5331 kg ha-1) over control. Further, in levels of iron sulphate and zinc sulphate higher straw yield found with application of 40 kg FeSO4 ha-1 (5612 kg ha-1) and 40 kg ZnSO4 ha-1 (5530 kg ha-1). Higher concentration of macro nutrients and micronutrients noted with application of Pseudomona striata + 40 kg FeSO4 ha-1 +40 kg ZnSO4 ha-1. Similarly, higher uptake of macro and micro nutrients found with microbial inoculant particularly Pseudomona striata and with application of 40 kg FeSO4 ha-1 and 40 kg ZnSO4 ha-1 along with recommended dose of fertilizers.

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Grain yield (kg ha-1): M0 (Control) vs M1 (Pseudomona striata) vs M2 (Pseudomona... vs M3 (Bacillus megaterium)Close ×

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Grain yield (kg ha-1): Fe0 (FeSO4 0 kg ha-1) vs Fe1 (FeSO4 20 kg ha-1) vs Fe2 (FeSO4 40 kg ha-1)Close ×

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Introduction

Over 2 billion people worldwide suffer from micronutrient deficiencies, primarily as a result of eating monotonous diets which is dominated in low-nutrient foods. (Bouis and Satzman 2017) [9] . Iron deficiency is the most widespread nutritional problem. It mostly impacts children's learning capacity as well as their physical and mental development. (Talpur et al. 2018) [30] . Deficiency of micronutrients mainly affects women and children. An estimated 45% of deaths of children under the age of 5 are linked to micronutrient malnutrition (Gernand et al. 2016) [13] . Iron deficiency can leads to a serious condition like anemia, which is also a prime cause of women's death during childbirth (Anuradha et al. 2017) [5] . The most popular diet among people living in developing nations, such as India, is vegetarianism, which mostly consists of cereals and legumes with restricted access to fruits, meat, eggs, and dairy products. etc. (Puranik et al. 2017) [26] . This low nutrient diet is the main cause of micronutrient deficiency. Further, zinc is essential for the proper development of the human body and its deficiency is ranked as the 5 th major risk factor for impairment (Anuradha et al. 2017) [5] . Its deficiency is particularly prevalent in children under 5 years old as they have a comparatively huge demand for zinc to sustain development (Black et al. 2008) [8] . Deficiency of zinc causes physiological problems such as hindrance in brain development, improper growth and augmented vulnerability to infectious diseases like pneumonia and diarrhea and low birth outcomes in pregnant women (Hambidge and Krebs 2007) [15] . The two most vital elements in the human body are iron and zinc.

A vegetarian person depends mainly on cereal based diet which is low in of Fe and Zn. Biofortification is an economical and sustainable way to challenge the micronutrient malnutrition problem worldwide (Tripti et al. 2022) [32] . Wheat is one of the most important staple food crops grown in India. It is important to increase Fe and Zn concentration in wheat. Agronomic biofortification is a strategy to increase micronutrient content in the edible part of food crops through the application of mineral fertilizers (White and Broadley 2009) [34] . This approach can enrich food crops with multiple elements at a time and can reach resource poor rural populations, providing they have access to fertilizers. Food crop micronutrient concentrations can be enhanced through agronomic biofortification, with the potential to reduce micronutrient deficiencies among rural population (Teklu et al. 2023) [31] .

Materials and Methods

The present investigations were conducted at research farm of Department of Soil Science and Agricultural Chemistry, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. The crop was sown on fixed layout in the months of November and was harvested in month of March in during both growing seasons. The crop variety used was NIAW-1994. The recommended dose of chemical fertilizers was applied @ 100:50:50 N and P 2 O 5 and K 2 O kg ha -1 through urea, SSP and MOP. A basal dose of fertilizer was applied as per treatment at the time of sowing to wheat. Irrigation was given as per crop need. The recommended package of practices was followed. The grain and straw yields were recorded from net plot area at maturity stage of the crop. Experimental study consists of four iron and zinc solubilizing cultures (Control, Pseudomona striata, Pseudomona fluorescens, and Bacillus megaterium), three levels of iron sulphate (0, 20 and 40 kg FeSO 4 ha -1 ) and three levels of zinc sulphate (0, 20 and 40 kg ZnSO 4 ha -1 ) replicated twice in factorial randomized block design. Seed inoculation was done with iron and zinc solubilizing microbial inoculants as seed treatment before sowing. Nutrient content in plant sample and grain were analyzed for nitrogen (Micro Kjeldhals method (AOAC, 1990), phosphorus (Vanadomolybdate phosphoric acid yellow colour method by Jackson, 1973) [18] , potash estimated by Flame photometer (Jackson, 1973) [18] , iron and zinc by Atomic Absorption Spectrophotometer. The results data obtained were analyzed using standard statistical procedure given by Panse and Sukhatme (1967) [23] .

Results

Results

Grain yield

The data in respect of grain yield of wheat as influenced by Fe and Zn solubilizing microbial inoculants and fertilizers application is presented in Table 1. Microbial inoculants positively and significantly influenced on grain yield which ranged between 2454-2869 kg ha -1 . The higher grain yield was noted in plots inoculated with Pseudomona striata (M 1 ) over control i.e. 2869 kg ha -1 .There was significant increase in the grain yield of wheat due to graded levels of iron and zinc sulphate as compared to control treatment. Grain yield of wheat influenced with graded levels of iron up to 40 kg ha -1 ranged between 2394-2881 kg ha -1 . The highest grain yield was noted in plots treated with 40 kg FeSO 4 kg ha -1 (2881 kg ha -1 ). Similarly, the grain yield influenced with application of zinc sulphate which ranged between 2404-2876 kg ha -1 . Maximum yield was noted in plots treated with 40 kg ZnSO 4 ha -1 (2876 kg ha -1 ) Straw yield: Data narrated in Table 1. related to straw yield of wheat was significantly influenced due to microbial inoculants and graded levels of iron sulphate and zinc sulphate. The significantly maximum straw yield was recorded in treatment with inoculation of Pseudomona striata (M 1 ) (5698 kg ha -), it was statistically at par with treatment M 3 (Bacillus megaterium) (5604 kg ha -1 ). Further, graded levels of iron and zinc in the form of FeSO 4 and ZnSO 4 also significantly influenced on straw yield of wheat. The significantly highest straw yield was recorded in the application of 40 kg FeSO 4 and ZnSO 4 ha -1 . Straw yield influenced with application of iron sulphate which ranged between 5111-5922 kg ha -1 . The maximum straw yield was noted in plots treated with 40 kg FeSO 4 kg ha -1 (5922 kg ha - 1 ). Similarly, the straw yield influenced with application of zinc sulphate which ranged between 5245-5757 kg ha -1 . Higher straw yield was noted in plots treated with 40 kg ZnSO 4 ha -1 (5757 kg ha -1 ).

Treatments	Grain yield (kg ha-1)	Straw yield (kg ha-1)
Microbial inoculants (M)
M0 (Control)	2454	5194
M1 (Pseudomona striata)	2869	5698
M2 (Pseudomona fluorescens)	2608	5428
M3 (Bacillus megaterium)	2569	5604
SE ±	33.51	65.66
CD at 5%	68.08	133.39
Levels of FeSO4 (Fe)
Fe0 (FeSO4 0 kg ha-1)	2394	5111
Fe1 (FeSO4 20 kg ha-1)	2600	5411
Fe2 (FeSO4 40 kg ha-1)	2881	5922
SE±	29.03	56.86
CD at 5%	58.97	115.52
Levels of ZnSO4 (Zn)
Zn0 (ZnSO4 0 kg ha-1)	2404	5245
Zn1(ZnSO4 20 kg ha-1)	2594	5441
Zn2 (ZnSO4 40 kg ha-1)	2876	5757
SE ±	29.03	56.86
CD at 5%	58.97	115.52

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Effect of microbial inoculants and graded levels of iron sulphate and zinc sulphate on grain and straw yield (kg ha-1)

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Macro nutrient content (NPK)

Nitrogen content (%): Iron and zinc solubilizing microbial inoculants and fertilizers showed significant effect on nitrogen content of straw and grain of wheat presented in Table 1. Microbial treatments influenced on nitrogen content which was ranged between 1.00-1.18 and 2.77-3.17% of straw and grain of wheat respectively. The highest nitrogen content in straw and grain noted with application of Pseudomonas striata i.e. 1.18% and 3.17% respectively. The levels of iron sulphate and zinc sulphate also influenced on nitrogen content. The iron sulphate up to 40 kg ha -1 influenced on nitrogen content which ranged between 0.95-1.25 and 2.72-3.14% of straw and grain respectively. The higher nitrogen content was noted in 40 kg FeSO 4 ha -1 (1.25 and 3.14% of straw and grain respectively). Similarly, levels of zinc sulphate up to 40 kg ha -1 influenced on nitrogen content which was ranged between 0.99-1.18 and 2.72-3.10% of straw and grain respectively. The higher nitrogen content was noted in 40 kg ZnSO 4 ha -1 (1.18 and 3.10% of straw and grain respectively).

Phosphorus content: It was evidence from data presented in Table 2. That phosphorus content of wheat straw and grain was positively and significantly influenced by microbial inoculation and graded levels of iron and zinc sulphate. The microbial inoculants influence on phosphorus content and highest phosphorus content noted with application of Pseudomona striata i.e. 0.39% for straw and for grain 0.84%. Scrutiny of data further revealed that, graded levels of iron and zinc in the form of FeSO 4 and ZnSO 4 also influenced the phosphorus content in straw and grain up to 40 kg ha -1 . For iron sulphate up to 40 kg FeSO 4 ha -1 influenced on phosphorus content of straw and grain and ranged between 0.25-0.46% and 0.67-0.91% respectively. For zinc sulphate up to 40 kg ZnSO 4 ha -1 influenced on phosphorus content and ranged between 0.29-0.40 and 0.72-0.85% for straw and grain respectively. Highest phosphorus content of straw and grain noted with 40 kg FeSO 4 ha -1 (0.46 and 0.91%for straw and grain respectively) and 40 kg ZnSO 4 ha -1 (0.40 and 0.85%for straw and grain respectively). Potassium content: Microbial treatments influenced on potassium content which was ranged between 1.05-1.23% and 0.55-0.73% of straw and grain of wheat respectively (Table 2). The highest potassium content in straw and grain influenced by Pseudomonas striata i.e. 1.23% and 0.73% respectively. The levels of iron sulphate and zinc sulphate also influenced on potassium content. The iron sulphate up to 40 kg ha -1 influenced on potassium content which ranged between 1.01-1.29 and 0.51-0.80% of straw and grain respectively. The higher potassium content was noted in 40 kg FeSO 4 ha -1 (1.29 and 0.80% of straw and grain respectively). Similarly, levels of zinc sulphate up to 40 kg ha -1 influenced on potassium content which was ranged between 1.04-1.23 and 0.53-0.75% of straw and grain respectively. The higher potassium content was noted in 40 kg ZnSO 4 ha -1 (1.23 and 0.75% of straw and grain respectively). Nitrogen uptake: Microbial treatments influenced on nitrogen uptake of straw and grain which was ranged between 52.62-68.00 and 68.24-92.67 kg ha -1 respectively. For total nitrogen uptake of wheat influenced by microbial inoculation and ranged between 120.87-160.67 kg ha -1 . The higher nitrogen uptake influenced by Pseudomona striata i.e. 68.00, 92.67 and 160.67 kg ha -1 for straw, grain and total respectively. The levels of iron sulphate and zinc sulphate also influenced on nitrogen uptake. The iron sulphate up to 40 kg ha -1 influenced on nitrogen uptake of straw and grain which ranged 48.62-74.50 and 65.56-91.56 kg ha -1 respectively. For total uptake of nitrogen ranged between 114.18-166.06 kg ha -1 . The higher nitrogen uptake was reported in 40 kg FeSO 4 ha -1 (74.50, 91.56 and 166.06 kg ha - 1 for straw, grain and total respectively). Similarly, levels of zinc sulphate upto 40 kg ha -1 influenced on nitrogen uptake which was ranged between 52.20-68.62, 65.56-90.83 and 117.76-159.45 kg ha -1 for straw, grain and total respectively. The higher nitrogen uptake was noted in 40 kg ZnSO 4 ha -1 (68.62, 90.83 and 159.45 kg ha -1 at straw, grain and total respectively).

Treatments	Nitrogen content (%)	—	Phosphorus content (%)	—	Potassium content (%)	—	Iron content (mg kg-1)	—	Zinc content (mg kg-1)	—
	Straw	Grain	Straw	Grain	Straw	Grain	Straw	Grain	Straw	Grain
Microbial inoculants (M)
M0 (Control)	1.00	2.77	0.30	0.73	1.05	0.55	201.53	426.03	38.55	50.71
M1 (Pseudomona striata)	1.18	3.17	0.39	0.84	1.23	0.73	204.90	431.90	43.59	56.37
M2 (Pseudomona fluorescens)	1.04	2.88	0.34	0.78	1.10	0.61	202.83	430.66	43.27	55.82
M3 (Bacillus megaterium)	1.14	2.91	0.35	0.79	1.18	0.68	203.65	428.33	42.54	53.40
SE ±	0.029	0.035	0.015	0.013	0.030	0.023	0.552	0.581	0.565	0.543
CD at 5%	0.060	0.070	0.031	0.026	0.062	0.047	1.122	1.180	1.147	1.104
Levels of FeSO4 (Fe)
Fe0 (FeSO4 0 kg ha-1)	0.95	2.72	0.25	0.67	1.01	0.51	200.45	426.41	39.72	51.74
Fe1 (FeSO4 20 kg ha-1)	1.07	2.93	0.33	0.77	1.12	0.62	203.00	428.96	41.53	53.92
Fe2 (FeSO4 40 kg ha-1)	1.25	3.14	0.46	0.91	1.29	0.80	206.23	432.33	44.71	56.57
SE±	0.025	0.030	0.013	0.011	0.026	0.020	0.478	0.503	0.489	0.471
CD at 5%	0.052	0.061	0.027	0.023	0.053	0.041	0.972	1.022	0.994	0.956
Levels of ZnSO4 (Zn)
Zn0 (ZnSO4 0 kg ha-1)	0.99	2.72	0.29	0.72	1.04	0.53	201.02	426.90	39.47	51.58
Zn1(ZnSO4 20 kg ha-1)	1.11	2.98	0.35	0.79	1.15	0.65	203.21	429.09	41.57	53.71
Zn2 (ZnSO4 40 kg ha-1)	1.18	3.10	0.40	0.85	1.23	0.75	205.45	431.71	44.93	56.93
SE ±	0.025	0.030	0.013	0.011	0.026	0.020	0.478	0.503	0.489	0.471
CD at 5%	0.052	0.061	0.027	0.023	0.053	0.041	0.972	1.022	0.994	0.956

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Effect of microbial inoculants and graded levels of iron sulphate and zinc sulphate on macronutrient and micronutrient content of

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Micronutrient content (Fe and

Micronutrient content (Fe and

Iron uptake:

The data narrated in Table 4. about iron uptake is given. Iron uptake of straw and grain estimated separately and total iron uptake was calculated. The microbial inoculants influence on iron uptake and ranged between 1047.75-1170.26, 1340.26-1585.51 g ha -1 for straw, grain and 2093.53-2411.55 g ha -1 for total respectively. The higher iron uptake recorded in Pseudomona striata i.e. 1170.26 g ha -1 for straw, 1585.51 g ha -1 grain and total iron uptake 2411.55 g ha -1 . This was superior over other treatments. The lower iron uptake was observed in uninoculated control treatment (1047.75, 1340.26 and 2093.53 g ha -1 for straw, grain and total respectively). Moreover, highest increase in total Fe uptake over control was reported in treatment M2 i.e. Pseudomonas striata (15.19 percent).Further, graded levels of iron and zinc in the form of FeSO 4 and ZnSO 4 also influenced on iron uptake in straw and grain upto 40 kg ha -1 .The iron uptake was ranged from 1024.42-1222.50 g ha -1 for straw, 1308.39-1592.75 g ha -1 for grain and 2045.53-2469.48 g ha -1 for total uptake. The highest iron uptake was noted in 40 kg FeSO 4 ha -1 which was (1222.50 g ha -1 ) for straw uptake (1592.75 g ha -1 ) for grain uptake and total iron uptake (2469.48 g ha -1 ). Furthermore, higher total Fe uptake over control reported @ 40 kg FeSO 4 ha -1 (20.72 percent) followed by 20 kg FeSO 4 ha -1 over control (8.30 percent). For levels of zinc sulphate iron uptake ranged between 1054.65-1185.19, 1314.89-1589.96 and 2081.08-2429.85 g ha -1 for straw, grain and total uptake respectively and higher iron uptake noted in 40 kg ZnSO 4 ha -1 which was straw (1185.19 g ha -1 ), grain (1589.96 g ha -1 ) and total uptake of iron (2429.85 g ha -1 ). Moreover, higher total Fe uptake over control reported @ 40 kg ZnSO 4 ha -1 (16.75 percent) followed by 20 kg ZnSO 4 ha -1 over control (6.65 percent).

Treatments	Iron uptake (g ha-1)	—	—	—	Zinc uptake (g ha-1)	—	—	—
	Straw	Grain	Total	% increase over control	Straw	Grain	Total	% increase over control
Microbial inoculants (M)
M0 (Control)	1047.75	1340.26	2093.53	-	201.40	125.11	326.50	-
M1 (Pseudomona striata)	1170.26	1585.51	2411.55	15.19	250.78	163.02	413.80	26.73
M2 (Pseudomona fluorescens)	1101.27	1437.50	2225.75	6.31	235.41	146.67	382.08	17.02
M3 (Bacillus megaterium)	1141.99	1409.49	2243.16	7.14	239.50	137.65	377.15	15.51
SE ±	12.985	18.468	20.559		4.412	2.612	6.186
CD at 5%	26.378	37.518	41.765		8.963	5.306	12.567
Levels of FeSO4 (Fe)
Fe0 (FeSO4 0 kg ha-1)	1024.42	1308.39	2045.53	-	203.74	124.19	327.93	-
Fe1 (FeSO4 20 kg ha-1)	1099.03	1428.43	2215.48	8.30	225.46	140.68	366.14	11.65
Fe2 (FeSO4 40 kg ha-1)	1222.50	1592.75	2469.48	20.72	266.11	164.46	430.57	31.29
SE±	11.245	15.994	17.804		3.821	2.262	5.357
CD at 5%	22.844	32.491	36.170		7.762	4.595	10.884
Levels of ZnSO4 (Zn)
Zn0 (ZnSO4 0 kg ha-1)	1054.65	1314.89	2081.08	-	207.59	124.31	331.90	-
Zn1(ZnSO4 20 kg ha-1)	1106.11	1424.72	2219.56	6.65	227.19	139.90	367.09	10.60
Zn2 (ZnSO4 40 kg ha-1)	1185.19	1589.96	2429.85	16.75	260.53	165.13	425.66	28.24
SE ±	11.245	15.994	17.804	-	3.821	2.262	5.357
CD at 5%	1054.65	32.491	36.170	-	7.762	4.595	10.884

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Effect of microbial inoculants and graded levels of iron sulphate and zinc sulphate on uptake of iron (g ha-1)

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Zinc uptake:

The data narrated in Table 4. regarding zinc uptake is given. Zinc uptake of straw and grain estimated separately and total zinc uptake was also calculated. Microbial treatments influenced on zinc uptake of straw and grain which was ranged between 120.40-250.78 and 125.11-163.02 g ha -1 respectively. For total zinc uptake of wheat influenced by microbial inoculation and ranged between 326.50-413.80 g ha -1 . The maximum zinc uptake influenced by Pseudomona striata i.e. 250.78, 163.02 and 413.80 g ha -1 for straw, grain and total respectively. Moreover, highest increase in total Zn uptake over control was noted in treatment M2 i.e. Pseudomonas striata (26.73 percent) followed by Pseudomonas fluorescens and Bacillus megaterium (17.02 and 15.51 percent respectively). The levels of iron sulphate and zinc sulphate also influenced on zinc uptake. The iron sulphate upto 40 kg ha -1 influenced on zinc uptake of straw and grain which ranged 203.74-266.11

and 124.19-164.46 g ha -1 respectively. For total uptake of zinc, it was influenced by iron sulphate and ranged between 327.93-430.57 g ha -1 . The higher zinc uptake was reported in 40 kg FeSO 4 ha -1 (266.11, 164.46 and 430.57 g ha -1 for straw, grain and total respectively). Further, higher total Zn uptake over control reported @ 40 kg FeSO 4 ha -1 (31.29 percent) followed by 20 kg FeSO 4 ha -1 over control (11.65 percent). Similarly, levels of zinc sulphate upto 40 kg ha -1 influenced on zinc uptake which was ranged between 207.59-260.53, 124.31-165.13 and 331.90-425.66 g ha -1 for straw, grain and total respectively. The higher zinc uptake was noted in 40 kg ZnSO 4 ha -1 (260.53, 165.13 and 425.66 g ha -1 at straw, grain and total respectively) which was superior over control treatment. The lower zinc uptake was recorded in control treatment (207.59, 124.31 and 331.90 g ha -1 at straw, grain and total respectively). Furthermore, higher total Zn uptake over control reported @ 40 kg ZnSO 4 ha -1 (28.24 percent) followed by 20 kg ZnSO 4 ha -1 over control (10.60 percent).

Discussion

Availability of sufficient amount of nutrients by solubilization of native status of nutrient present in soil and increased uptake of nutrients and their utilization increased metabolism and synthesis of carbohydrates, better vegetative growth and subsequent partitioning and translocation from to head and also release of energy rich compounds by the biofertilizers which ultimately increased auxin activities, growth and activity of microbial saprophytes and phosphates activity which ultimately affect the yield and yield attributes (Choudhary et al. 2014) [10] .

Our results also correspond with the findings of Kandoliya et al. (2018) [19] reported significantly highest grain yield (4786 kg ha -1 ) was observed for the treatment T 12 (RDF + Soil application of ZnSO 4 @ 10 kg ha -1 + FeSO 4 @ 20 kg ha -1 ) which was almost 38.2 percent higher as compared to control treatment (N-P-K: 120-60-60 kg ha -1 ). Cotton yield was significantly increased with application of RD + soil application of FeSO 4 @ 25 + ZnSO 4 @ 20 kg ha -1 reported by Durgude et al. (2014) [11] . N, P and K absorption by plants increased by PGPR supply which decreased rhizosphere soil pH due to increased concentrations of organic acids and antioxidative activity. As a result of root exudation mediated rhizosphere acidification, growth enhancement by PGPR supply was associated with increased plant antioxidation activity as well as nutrient uptake Israr et al. (2016) [17] . Kapadia et al.

(2021) [21] stated that inoculation of microbial strains enhanced the more secondary roots, which store and transport more mineral nutrients to the various regions of the plant, resulting in increased biomass, nutrient contents, uptake and growth. Increase in the nutrient content in the plants showed that more bioavailability of available nutrients in soil solution and also supply of added fertilizers. Microbial isolates release the different organic acids make the nutrient available to crop plant. Similar findings reported by Hassan and Bano (2015) [16] reported that carrier-based biofertilizer enhanced the growth of wheat and also stated that the application of biofertilizer increased nutrients content and uptake of wheat over control treatment. The similar results confirmed with findings of Pawar et al.

(2015) [25] concluded that soil application of 15 kg ZnSO 4 ha - 1 + 15 kg FeSO 4 ha -1 with recommended dose of fertilizers recorded highest NPK concentration in grain and fodder of kharif sorghum. The enhancement of micronutrient concentration by plants may be due to microbial inoculation with additional supplement of fertilizers may effect on initiation and development of effective roots system and nutrient uptake also increased in iron content of leaves and grain was might be due to increased iron availability in soil due to siderophore producing ability (Schwyn and Neilands 1987).

Pseudomonas fluorocens (52.83%) CAS medium shows maximum siderophore production followed by Pseudomonas striata (48.33%) and Bacillus megaterium (46.67%) reported by Akshay et al. (2023) [2] . The maximum available Fe and Zn was noticed under RDF + 25 kg ha -1 FeSO 4 +25 kg ha -1 ZnSO 4 reported by Waikar et al. (2021) [33] . Parmer et al. (2020) [24] concluded that higher content of Fe recorded with 25 kg ha -1 ZnSO 4 +50 kg ha -1 FeSO 4. Further, similar findings reported by Habib (2009) [14] and Kandoliya and Kunjadia (2018) [19] . The increased nutrient uptake may be due to greater availability of nutrients through inorganic and biological sources and well-developed root system. The increased uptake was also due to added supply of nutrients, balanced nutrient application and acid secretions by the microbial cultures might have acted on unavailable K in soil and made it more available for wheat crop resulting in better absorption of water and nutrients Sheng (2005) [29] . The maximum N, P and K uptake by pearl millet grain and stover was noticed in treatment consisting of RDF + 25 kg ha -1 FeSO 4 + 25 kg ha -1 ZnSO 4 reported by Waikar et al. (2021) [33] Increase in Fe uptake might be due to siderophores produced by rhizosphere microorganisms are iron chelating ligands which can be beneficial to plants can supply iron to plants under iron stress or iron limiting conditions by increasing the solubility of ferric iron (Fe III), which otherwise is unavailable for plant nutrition. This element is assimilated by root cells in the reduced form (Fe II); however, especially in sufficiently aerated soils, the oxidized state (Fe III) is predominant and needs to be reduced to be taken up by plants. Plant roots have receptors or channels which can receive microbial siderophore, and plant ferric reductase helps in unloading of iron and converting it to the ferrous form (Altomare et al. 1999) [4] . Moreover, supply of additional iron through fertilizers also play important role in increasing more uptake by wheat crop. The research of this investigation are in consonance with the findings of Sable et al. (2016) [27] reported the content and uptake of Fe, Zn, Mn and Cu by groundnut was also found to be significantly highest with the inoculation of RDF + Rhizobium + Pseudomonas striata. Kiran et al. (2017) [22] reported highest increase in Fe uptake (4850 g ha -

1

) in treatment T 7 (GRDF + 20 kg ZnSO 4 ha -1 + 25 kg FeSO 4 ha -1 + seed inoculation of Fe and Zn solubilizers) over other treatments in wheat crop. Similarly, Parmer et al. (2020) [24] reported higher uptake of Fe noted with 25 kg ha -1 ZnSO 4 + 50 kg ha -1 FeSO 4. The treatment RDF+ 25 kg ha -1 FeSO 4 + 25 kg ha -1 ZnSO 4 recorded the significantly highest iron uptake reported by Waikar et al. (2021) [33] noted that highest iron uptake in treatment RDF + 25 kg ha -1 FeSO 4 +25 kg ha -1 FeSO 4 and lowest iron uptake was observed in absolute control. Enhanced Zn uptake might be due to solubilization of insoluble soil Zn by production of gluconic acids by the bacterial sp. Like Pseudomona striata, Pseudomona fluorescens and Bacillus megaterium. The bacterial inoculation increased Zn uptake at all ZnSO 4 application levels. Zn-solubilizers, owing to the organic acid production and proton extrusion (H+), lowers the rhizospheric pH, which sequesters zinc cations and improves uptake by plants. (Alexander 1997 [3,2,35,6] . The experimental findings are confirmed with Waikar et al. (2021) [33] reported that highest zinc uptake was noted with treatment RDF + 25 kg ha -1 FeSO 4 + 25 kg ha -1 ZnSO 4 and the lowest zinc uptake was observed in absolute control. Parmer et al. (2020) [24] reported higher uptake of Zn noted with 25 kg ha -1 ZnSO 4 + 50 kg ha -1 FeSO 4. Similar findings reported by Kiran et al. (2017) [22] and Banafsheh et al. (2022) [7] .

Conclusion

Seed inoculation with microbial inoculants (Iron and zinc solubilizer) + soil application of Fe and Zn in the form of FeSO 4 and ZnSO 4 along with RDF found beneficial in improving the yield, concentration and nutrient uptake of wheat crop. Microbial inoculant particularly Pseudomonas striata and 40 kg FeSO 4 ha -1 and 40 kg ZnSO 4 ha -1 noted higher yield, nutrient concentration and uptake of nutrients by wheat.

Figures and tables from the paper

Treatments	Nitrogen uptake (kg ha-1)	—	—	Phosphorus uptake (kg ha-1)	—	—	Potassium uptake (kg ha-1)	—	—
	Straw	Grain	Total	Straw	Grain	Total	Straw	Grain	Total
Microbial inoculants (M)
M0 (Control)	52.62	68.24	120.87	15.98	18.21	34.19	55.48	13.91	69.39
M1 (Pseudomona striata)	68.00	92.67	160.67	22.92	24.65	47.58	70.69	21.65	92.33
M2 (Pseudomona fluorescens)	56.81	75.91	132.73	18.69	20.86	39.55	60.17	16.68	76.85
M3 (Bacillus megaterium)	64.33	75.16	139.48	19.90	20.52	40.42	66.62	17.69	84.31
SE ±	1.819	1.410	2.535	0.831	0.520	1.254	1.834	0.583	2.341
CD at 5%	3.695	2.865	5.150	1.688	1.057	2.547	3.727	1.185	4.756
Levels of FeSO4 (Fe)
Fe0 (FeSO4 0 kg ha-1)	48.62	65.56	114.18	12.86	16.31	29.17	51.76	12.52	64.28
Fe1 (FeSO4 20 kg ha-1)	58.20	76.87	135.07	18.02	20.38	38.39	60.90	16.45	77.35
Fe2 (FeSO4 40 kg ha-1)	74.50	91.56	166.06	27.25	26.48	53.74	77.06	23.48	100.54
SE±	1.575	1.221	2.195	0.720	0.451	1.086	1.589	0.505	2.027
CD at 5%	3.200	2.481	4.460	1.462	0.915	2.206	3.227	1.026	4.119
Levels of ZnSO4 (Zn)
Zn0 (ZnSO4 0 kg ha-1)	52.20	65.56	117.76	15.32	17.58	32.90	55.18	12.95	68.13
Zn1(ZnSO4 20 kg ha-1)	60.51	77.59	138.10	19.04	20.62	39.67	63.04	17.15	80.19
Zn2 (ZnSO4 40 kg ha-1)	68.62	90.83	159.45	23.76	24.97	48.74	71.50	22.35	93.85
SE ±	1.575	1.221	2.195	0.720	0.451	1.086	1.589	0.505	2.027
CD at 5%	3.200	2.481	4.460	1.462	0.915	2.206	3.227	1.026	4.119

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Effect of microbial inoculants and graded levels of iron sulphate and zinc sulphate on uptake of macronutrients (kg ha-1)

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