Growth, nutrient uptake and yield of ginger as impacted by potting media, foliar nutrition and microbial inoculants

Experiments were conducted during 2017-19 at the Integrated Farming System Research Station, Karamana, Kerala Agricultural University for assessing the impact of quantity of potting media, foliar application of multinutrient mixture IISR Power Mix G and microbial inoculants Arbuscular Mycorrhizal Fungi (AMF) and Trichoderma on the growth, nutrient uptake and yield of ginger variety Karthika grown as pot culture. The study revealed that 12 and 15 kg of potting media filled grow bags could produce comparable yields of ginger significantly higher than that obtained with 9 kg of potting media. Application of IISR Power Mix G @ 0.5% at 2 and 3 months of planting enhanced the yield of ginger to the tune of 11 per cent in comparison to control. Microbial inoculants AMF (5 g plant-1) and Trichoderma (1 kg mixed with 90 kg FYM and 10 kg neem cake and 250 g of the mixture used) applied at planting time followed by Trichoderma at 1 month after planting resulted in higher fresh ginger yield of 596.67 g bag-1 and was comparable to 550 g of fresh ginger obtained with application of AMF and Trichoderma at planting.


Introduction
Ginger (Zingiber officinale) occupies a prime position among spice crops in India. India is a major producer and grows ginger in an area of 1.17 lakh ha accounting to an annual production of 5.29 lakh tons with an average productivity of 4.3 t ha -1 (Spices Board 2018). In Kerala, ginger is an integral crop component of homesteads grown for its medicinal value and year round demand for both fresh vegetable and dried spice. There are reports of successful cultivation of ginger in homesteads using growbags (Abraham 2016) and gunny bags (IISR 2016; Krishi Jagaran 2019). However, not much work was conducted to standardize an optimum quantity of container media for growing ginger and hence the present experiment aimed to address this issue.
Soil limitations can lead to nutrient deficiencies and foliar nutrition is well established as a corrective factor in overcoming such limitations. There are reports on improved growth and yield of ginger with ZnSO 4 (0.5%) spray (Singh & Dwivedi 2007). Foliar fertilizers with slow release rate are thus effective in counteracting the reduced mobility and bioavailability of Zn (Doolette et al. 2018). Supplemental foliar nourishment is a booster to attain better yield by correcting soil limitations.
Bioinoculants like AMF and Trichoderma through their growth promoting effects are reported to enhance crop yields. They are reported to improve root development leading to better nutrient uptake by crops and hence higher yields. Additionally, tolerance to abiotic stress and resistance against plant pathogens are also reported with the use of these bio inoculants (Bharat 2017). AMF inoculation also helps selective activation of beneficial soil microbes (Tahat & Sijam 2012). AMF belonging to Gigasporaceae have revealed prominent nutrient uptake capacity compared to plant protection effects, whereas the members of Glomeraceae ensured more of protection from pathogen invasions (Maherali & Klironomos 2007). Hence the present study also aimed at developing a production package for better yield of ginger through the inclusion of bio inoculants and foliar spray of IISR Power mix G in the crop management schedule.

Materials and methods
The experiment was conducted at the Integrated Farming System Research Station (IFSRS), Kerala Agricultural University, Karamana, Thiruvananthapuram, Kerala (8 0 48' 18'' N Latitude and 76 0 96' 57''E Longitude). The ginger variety used was Karthika developed by Kerala Agricultural University (selection from cv. Maran through tissue culture and somaclonal variation techniques). The study was conducted as two experiments as mentioned below.

Weight of growing media and multinutrient foliar sprays on the growth and yield of ginger grown in grow bags
The two factors studied under this experiment were quantity of potting media (P) and crop nutrition (N). The design of the experiment was Factorial CRD with three replications. The potting media was prepared by mixing red soil, rock sand, coir pith and FYM in the ratio 1: 0.5: 0.5:1 on volume basis and was enriched with neem cake (4.8% N) @50 kg per 500 kg mixture. The initial nutrient status of the mixture was 303 kg available N, 26 kg P 2 O 5 and 280 kg K 2 O ha -1 and 80, 0.41 and 1.26 mg kg -1 of Mg, B and Zn. Nutrients, pH and organic carbon were estimated as per standard procedures (Jackson 1973) including Microkjeldhal method (N), nitric -perchloric acid digestion and spectrophotometry using Vanadomolybdophosphoric yellow colour method (P) and Nitric -perchloric acid digestion and Atomic Absorption Spectrophotometry (Zn). B was estimated based on azomethine method and Mg through EDTA titration method. Potting media had a pH of 6.10 and the organic carbon content was 1.34%. Measurement of pH was done using pH meter with glass electrode and organic carbon was determined using the Walkely and Black rapid titration method.
Five plants were maintained per replication. The rhizomes were sown in protrays, which were transplanted in grow bags at one month after sowing. Periodic observations on growth attributes were recorded and the crop was harvested at 9 months of planting. Observations on fresh and dry ginger yield and root growth in terms of root length and root biomass were recorded at harvest. Dry ginger recovery was estimated by drying known weight of fresh ginger in hot air oven at a temperature of 60 o C for 48 hours, wherein the moisture content of rhizomes was reduced to a level of 10%.

Microbial inoculants in improving growth and yield of ginger
Based on the conclusions of Experiment I, a promising package for grow bag grown ginger was arrived (Potting media @12 kg/bag, organic crop nutrition, supplemental foliar spray of multinutrient mixture IISR Power mix G (0.5%) at 60 and 90 DAS). This was decided as control (T 7 ) treatment and was uniformly followed for all treatments. Further improvement in crop productivity using microbial inoculants was studied in Experiment II. Bio inoculants were imposed on all treatments except control as follows -T 1 (AMF at planting), T 2 (Trichoderma at planting), T 3 (Trichoderma at planting and 30 DAP), T 4 (AMF+ Trichoderma at planting), T 5 (AMF + Trichoderma at planting followed by Trichoderma at 30 DAP) and T 6 (Trichoderma @30 days interval throughout the crop growth).
The species of bioinoculants were Trichoderma sp. (KAU formulation) and AMF (KAU) including Glomus fasciculatum, G. acaulospora, G. mossaea, G. etunicatum and Gigaspora sp. AMF was applied @ 5 g plant -1 during planting of rhizomes in growbags. Trichoderma (1 kg) was multiplied in cowdung -neem cake mixture prepared in the ratio 90:10 kg. The mixture was incubated for 2 weeks and was applied @ 250 g per grow bag.
The design of the experiment was CRD with three replications. The initial nutrient status of the potting mixture was 298 kg of available N, 25 kg P, 285 kg K ha -1 and 78, 0.42 and 1.22 mg kg -1 of Mg, B and Zn. The pH of the mixture was 6.2 and organic carbon content was 1.28 per cent. Five observational plants were maintained per replication. Rhizomes were sown in protrays and the sprouted rhizomes were transplanted in grow bags after one month of sowing. Periodic observations on growth attributes were recorded. The crop was harvested at 9 months after planting and the observations on yield, root biomass and root length were recorded. Plant samples were analysed for major nutrients and uptake recorded. The data generated were subjected to statistical analysis and the significance tested as per analysis of variance (Panse & Sukhatme 1967).

Weight of growing media and multinutrient foliar spray Growth characters
Growth characters including plant height, number of tillers and number of leaves were observed at two stages i.e., 3 and 6 months after sowing (Table 1). At 3 MAS, none of the treatments could significantly influence the growth parameters studied. However, at 6 MAS, all the growth parameters were comparable for ginger plants grown in bags holding 12 and 15 kg media which was significantly superior to those grown in bags holding 9 kg of the media. With increase in the quantity of growing media, nutrient addition was more in bags of bigger size compared to lesser size bags resulting in enhancement in growth parameters.
Regarding crop nutrition, none of the treatments produced a significant impact on the growth characters at 3 months. However at 6 MAS, the treatments which received foliar nutrition of IISR Power mix G ie., N 2 (Package of Practices Recommendation for crops as per KAU + IISR Power mix G as foliar spray) and N 4 (Organic nutrition + IISR Power mix G as foliar spray) recorded higher and comparable growth attributes significantly superior to no application of IISR Power mix as in N 1 and N 3. This suggests that ginger being an exhaustive crop, recommended crop nutrition if supplemented with such foliar feeds could result in improved growth. The foliar nutrient formulation had Mg, Zn and B nutrients added in it, which are known for growth promotion. Mehta et al. (2017) observed a similar improvement in growth attributes of garlic when the crop was provided with supplemental foliar nutrient sprays. When plants are exposed to high Zn concentration, absorbed Zn via roots get complexed with P compounds to form Zn phytate, as a defense mechanism to prevent further translocation to shoots (Kopittke et al. 2011). This detoxification mechanism decreases the mobility and bioavailability of Zn in leaves. Foliar fertilizers with slow release rate are effective in counteracting such type of reduced mobility and bioavailability of nutrients (Doolette et al. 2018).

Root growth, dry matter production and nutrient uptake
The root length (38.98 cm) and root weight (159.1 g) were found higher for plants grown in grow bags holding 15 kg of potting media and were comparable to plants grown in 12 kg bags (37.21 cm and 153.39 cm respectively) ( Table 2). This can be related to the enhanced nutrient supply ensured with increase in quantity of potting media. Also, the container width was more for grow bags holding 15 and 12 kg media allowing horizontal proliferation of roots. Supplemental foliar sprays of IISR Power mix in treatments N 2 and N 4 improved the root growth significantly compared to non application. Root growth was found significantly reduced in 9 kg bag possibly due to space constraint for root proliferation and lower nutrient availability.
Grow bags holding higher quantities (15 and 12 kg) of the potting media recorded higher dry matter production of 142.77 and 137.36 g plant -1 respectively, significantly higher than that recorded with 9 kg media (117.48 g plant -1 ). Foliar sprays of IISR Power mix could significantly improve the dry matter production (DMP) compared to no foliar sprays due to enhancement in shoot and root growth (Tables  1 & 2).
The uptake of major nutrients nitrogen, phosphorus and potassium by the crop was significantly higher in grow bags holding 15 kg of the potting media compared to 12 and 9 kg bags. The treatments which received supplemental nutrient sprays could register significantly higher uptake of all these major nutrients compared to no application. Supplemental foliar spray of IISR Power mix (N 2 and N 4 ) also enhanced the DMP significantly over no application.

Yield
Plants raised in bags having higher quantity of media (15 and 12 kg) recorded fresh ginger yields of 468.75 and 447.5 g plant -1 respectively and were significantly superior to those grown in bags containing 9 kg (372.08 g plant -1 ) ( Table   Table 1 3). Regarding dry ginger yields also, the same trend followed and bags which had 15 and 12 kg media recorded significantly higher dry ginger yields compared to 9 kg bags. Significantly higher yields were recorded with supplemental foliar sprays of IISR Power Mix G, attributed to well balanced nutrition.

Growth characters
The growth characters studied were plant height, number of tillers and number of leaves plant -1 (Table 4). At 3 MAS, none of the treatments could significantly influence the plant height as well as tiller number plant -1 . However, leaf number was significantly influenced by treatment T 5 (AMF and Trichoderma at planting followed by Trichoderma at 30 DAP) registering higher leaf number of 55.55 comparable to that of 54.61 by treatment T 4 (AMF and Trichoderma at planting). The leaf number was the least with T 7 (40.4). At 6 months stage, all the treatments significantly influenced crop growth with treatments T 4 and T 5 registering comparable and superior performance for all the attributes studied compared to other treatments.

Root growth, dry matter production and nutrient uptake
Root growth (Table 5) in terms of length of roots were comparable for 3 treatments viz., T 5 (53.36), T 4 (51.44) and T 6 (49.0) and significantly higher than other treatments. Similar trend was noticed for root biomass also. Treatments T 5 and T 4 registered comparable and higher DMP of 188.6 and 179.03 g plant -1 respectively, followed by T 6 (171.82 g). Improved growth in terms of plant height, tiller number and leaf number as noticed in these treatments (Table 4) could be related with higher DMP. Uptake of nitrogen and potassium worked out for 200 plants was higher and comparable for treatments T 5 (309.31 and 350.8 kg ha -1 respectively) and T 4 (296.70 and 336.08 kg ha -1 ). Phosphorus uptake was significantly highest for treatment T 5 . Improvement in nutrient uptake could be linked to higher dry matter production (Table 5).

Yield
Treatments T 5 and T 4 registered significantly higher and comparable yields of 596.67 and 550.0 g plant -1 respectively (Table 6). This was followed by treatment T 6 (Trichoderma applied at 30 days interval throughout entire crop growth) which registered an yield of 523.33g plant -1 . Several workers have reported the significant effect of AMF in improving the yield of ginger (Santos 2010;Yunus et al. 2014;Abbasi et al. 2015;Li et al. 2015;Hijri 2016). Beneficial effects of Trichoderma in improving crop growth has been  Lopez-Bucio et al. 2015). Enhancement in uptake of nutrients is reported as a major growth promoting effect (Anil & Lakshmi 2010;Zhang et al. 2013;Saravanakumar et al. 2013). Trichoderma inhibits plant pathogens which helps in overcoming biotic stress, ensuring enhanced crop productivity (Paudel et al. 2017). Simultaneous application of Trichoderma and AMF is reported to have various positive and synergestic effects on crop growth (Medina et al. 2011;Poveda et al. 2019). Compatibility of these bio inoculants is revealed from favoured colonisation of Trichoderma in the presence of AMF, which in turn helps better nutrient uptake leading to yield improvement.

Economics of crop production
Treatment T 5 was significantly superior in generating higher gross and net returns as well as B:C ratio (Table 7). This was followed by T 4 . Based on the results of Experiment I, 12 and 15 kg potting media were on par with respect to ginger production. Hence considering resource and cost effectiveness, 12 kg media can be recommended for grow bag cultivation of ginger. As per the study, micronutrient mixture IISR Power mix G could enhance ginger yields by 11 per cent. INM package of KAU as well as organic crop nutrition were also equally good. Considering the fact that a majority of homestead farmers make use of terraces for cultivation, foliar application of IISR Power mix G could be recommended along with organic nutrition in ginger nutrition schedule.
The results of Experiment II reveal that bioinoculants AMF and Trichoderma conjunctively included in ginger cultivation schedule can enhance the yield. Yield increase of 25 per cent is evident from Table 6. With the application of bioinoculants AMF and Trichoderma at planting followed by Trichoderma at 30 DAP, 596.67 g fresh ginger was produced plant -1 , compared to 478.33 g fresh ginger plant -1 obtained with no application of bioinoculants. Based on these two experiments, it could be concluded that 12 kg of potting media is optimum for grow bag grown ginger and multinutrient mixture (IISR Power mix G) when supplemented with the recommended nutrition (organic/integrated) could enhance ginger yields to the tune of 11 per cent. Further enhancement in ginger yield is possible with the use of bioinoculants. AMF and Trichoderma when conjunctively used in ginger production could enhance yield up to 25 per cent.