Effect of Arbuscular Mycorrhizal Fungi and Different Combination of Foliar Application of Nutrients on Nutrient Uptake and Yield of Aerobic Rice

Rice (Oryza sativa L.) is main cereal grain crops. It feeds up more than half of the global population (Carrijo et al., 2017). Due to an over explosion in industrial and economic growth and rapid urbanization causes to meet the demand for food. It will be a great challenge in future food security (Fahad et al., 2017; Fukase and Martin, 2020). Since, it has been pointed out that global rice production want to be increase by approximately 20% by the year of 2030 and 30% before 2050. (Peng et al., 2009 and Shew et al., 2019). Currently, increases in labour rates, fertilizer costs and water requirements in conventional rice production methods result in lower profits (Nawaz et al., 2022), which has a direct impact on the farmer life. So, to come over that, farmers would go for aerobic rice cultivation. Aerobic rice is a novel cultivating technology that will be used as an alternative to flooded agriculture. The nutrition factor is the critical one in the yield realization of the aerobic rice ecosystem. The major consequence of inadequate nutrients is reduced leaf area, thereby limiting the following factors such as light interception, photosynthesis, biomass growth, grain yield and water productivity. Nutrient use efficiency was very poor in aerobic rice cultivation method, the presence of AM (Vesicular Arbuscular Mycorrhiza) fungi plays an important role to mobilize the nutrients which increasing their availability and ensuring those nutrients to crop during all growth stages. AM fungi significantly increased the nutrient concentration in shoot and root, grain and straw yield of rice under aerobic condition (Li et al., 2011). Micronutrients such as iron and zinc deficiency is major nutritional deficiency have been found in aerobic rice cultivation. Therefore present study formulated to mitigate the nutrient deficiency at early stage of aerobic rice. AM fungi and foliar application of nutrients is an option to correct such nutritional deficiencies of iron and zinc in aerobic rice.

Experimental site
 
During the month of January 2022, the research trial was conducted in wetland Farms situated at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore. The experimental site is geographically located at 11°N latitude and 77°E longitude at the height of 426.72 m above mean sea level. The soil type of the experimental site was clay loam in texture with  pH range of 7.84 and EC was 0.51 dsm^-1. The initial soil fertility status indicated low available KMnO₄ - N (225 kg ha^-1) (Asija and Subbiah, 1956), medium in available Olsen P (20.5 kg ha^-1) (Olsen, 1954) and high in available NH₄ O Ac - K (740 kg ha^-1) (Stanford et al., 1949).
 
Experimental design and treatment
 
Rice variety CO 53 (Duration 115 to 120 days, average yield - 3.7 to 3.8 t ha^-1, white short bold rice) was used in this experiment. The research trial field was designed with 13 treatments that were replicated three times in a Randomised Block Design. An individual plot sizes of 1 m × 1 m. The treatments include foliar applications of urea, iron (FeSO₄) and zinc (ZnSO₄), as well as soil applications of AM fungus (Table 1).
 

 
Crop management
 
Paddy seeds were directly sown in dry soil during Navarai season (Dec-Jan) with the spacing of 20 × 10 cm. Recommended dose of fertilizers (150 : 50 : 50 kg ha^-1 of N, P and K ) was given as a split application. N was given as four splits 20% at 15 DAS, 30% at tillering and panicle initiation stage and 20% at flowering. Full dose of P was given as basal application and K was given as 50 % at basal and 50% at panicle initiation stages. Foliar application of Urea, Iron (Fe) and Zinc (Zn) were given on 25^th and 45^th DAS.  Application of 100%, 125%, 150% recommended dose of VAM spores (50, 62.5, 75 kg ha^-1) along with farmyard manure was basally applied on before sowing. Crop was irrigated twice in a week with depth of 3 - 4 cm. Weed, pest and disease management was done as per the TNAU CPG 2020.
 
Nutrient uptake analysis
 
Total nitrogen was estimated by Kjeldahl distillation (Jackson, 1973), total phosphorous by Spectrophotometer (Jackson, 1973), total potassium by Flame photometry (Jackson, 1973) and micronutrients (Lindsay and Norvell, 1978) by Inductively Coupled Plasma Optical Emission spectroscopy (ICP - OES).
 
Statistical analysis
 
Data were analysed for Randomized Block Design by using SPSS 16.0. software to find the significance difference at 5 % level was used to test for significant differences among 13 treatment means. The relationship between total VAM colonization percentage with nutrient uptake of root and shoot of rice was assessed by Pearson correlation analysis using R software version 4.2.0 (RStudio 2022.02.3+492).

Nutrient uptake in shoot biomass
 
Macro and micronutrients uptake was significantly affected by soil application of VAM and foliar application of urea, zinc and iron. At 30 DAS application of 150% VAM + foliar application of 0.5% urea + 0.5% ZnSO₄ + 1% FeSO₄ at 25 and 45 DAS (T₁₃) exhibited a positive impact on nutrients uptake of N (27.2 kg ha^-1), P (6.6 kg ha^-1), K (39.7 kg ha^-1), Fe (648 g ha^-1) and Zn (106 g ha^-1) of shoot biomass respectively (Table 2). Lowest nutrient uptake of macro and micronutrients were recorded in control. At 50 DAS the plot fertilized with 150% soil application of VAM combined with foliar application of 0.5% urea + 0.5% ZnSO₄ + 1% FeSO₄ at 25 and 45 DAS (T₁₃) increased the nutrients uptake of  N (34.3 kg ha^-1), P (20.9 kg ha^-1), K (42.9 kg ha^-1), Fe (325 g ha^-1) and Zn (54 g ha^-1) of shoot biomass respectively. VAM fungi develop and spread through their external hyphae and cover the 8 cm area around the rhizosphere of the plant root system. Fungi expand the nutrient absorption range and surface area, which increase the nutrient uptake by plants. Primary nutrients (N, P and K), secondary nutrients (Ca and Mg) and micronutrients (Cu, Fe, Zn and Mn) can be more efficiently absorbed by plant root hairs when VAM fungi are present. These results line up with Abd-Alla et al., (2014). With respect to foliar application of 0.5% urea, 1% FeSO₄ and 0.5% ZnSO₄ at different growth stage in aerobic rice crop resulted in maximum iron and zinc uptake in shoot biomass. Soil application of FeSO₄ and ZnSO₄ results in adsorption to soil colloids and precipitation thereby reduced the availability of Zn and Fe (Recena et al., 2021). Foliar application of nutrients, alternate method of application, increased the Zn and Fe content and uptake (Phuphong et al., 2018).
 

 
Nutrient uptake in root biomass
 
At 30 and 50 DAS application of 150% VAM + foliar application of 0.5% urea + 0.5% ZnSO₄ + 1% FeSO₄ at 25 and 45 DAS (T₁₃) exhibited a positive impact on nutrients uptake of N (9.6 and 15.7 kg ha^-1), P (4.0 and 12.3 kg ha^-1) and K (9.9 and 15.0 kg ha^-1) of root biomass respectively (Table 3). Applying macro and micronutrients maximises the crop growth and output every time. When nutrients were abundant in the soil, plants were better able to absorb them, which had a major favourable impact on crop development and output. These findings match with results of (Bernardo et al., 2017).  According to the current study, applying foliar nutrients and VAM fungus to the soil together boosted the rice crop’s ability to absorb nutrients. Due to their symbiotic connection, VAM fungi aid in the greatest availability of nutrients by assisting plant roots in absorbing fertiliser. These results were consistent with those of Maiti et al., (2015) and Narwal et al., (2018). Saboor et al., (2021) and Okonji et al., (2018) stated that, soil having low pH level, Fe and Al activity, VAM fungi application significantly limits the nutrients absorption soil colloids. Prolonged application of VAM fungi ultimately improves the soil fertility status.
 

 
Yield traits
 
The yield traits viz., number of filled grains panicle^-1 (164), grain yield (3702 kg ha^-1), straw yield (4608 kg ha^-1) and Harvest index were influenced by different doses of soil application of VAM coupled with foliar application of Urea, Iron (Fe) and Zinc (Zn) (Table 4). The yield traits increased with 150% of recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO₄ + 1% FeSO₄ at 25 and 45 DAS (T₁₃). However, straw yield and harvest index was on pair with T₁₂. The presence of VAM fungi and foliar feeding of nutrient alter nutrient availability and absorption of nutrients at all stages of the crop, resulting higher yield traits under aerobic condition. These results are in confirmation with the results of Khan et al., (2022); Aziez et al., (2022). The inoculation VAM fungi can assist the host plant in absorbing nutrients required for photosynthesis and boost the yield (Bahadur et al., 2019).
 

 
Correlation analysis
 
Correlation analysis was carried out for total VAM colonization percentage and nutrient uptake of the aerobic rice. Results showed that shoot uptake of nitrogen (0.63), phosphorous (0.53), potassium (0.61), iron (0.63) and zinc (0.63) of aerobic rice observed were positively correlated with total VAM colonization percentage. Similarly root uptake of nitrogen (0.55), phosphorous (0.53) and potassium (0.58) of aerobic recorded positive correlation with total VAM colonization percentage (Fig 1). Comparatively shoot uptake was highly positive correlation than root uptake of aerobic rice.
 

Based on the discussion, it can be concluded that application of 150% of the recommended dose of VAM (75 kg ha^-1) along with foliar spray of 0.5% urea + 0.5% ZnSO₄ + 1% FeSO₄ at 25 and 45 greatly enhanced nutrient absorption and yield and yield traits under aerobic circumstances.

The authors declare that there is no conflict of interest.