Seed production performance of fodder sorghum in a Gliricidia sepium based Silvopastoral system

Introduction

The livestock sector plays a pivotal role in the Indian economy, contributing approximately 5.5% to the nation's Gross Value Addition (GVA) (GOI, 2022). One of the major constraints affecting livestock productivity is the acute shortage of green fodder, which is currently estimated at a deficit of about 36% (Singh, 2019) [7,13] . One of the reasons for deficit of green fodder production is due to non availability of quality seeds. The major problems in forage seed production are that forage crops are shy seed producers and harvested before seed setting to feed the animals, thereby restricting seed production (Kumar et al., 2015). Besides, farmers and other agencies do not take much interest to produce seed for their requirement and prefer to purchase from other sources. Consequently, a substantial gap persists between the demand and supply of quality forage seed across the country. (Chandra, 2020) [1] . Sorghum, besides being fifth most important cereal crop of the world, is also valued for its fodder and stover. Forage sorghum plant grows 6 to 12 feet tall and produces more dry matter tonnage than grain sorghum (Pandey and Roy, 2011) [8] . Globally sorghum is the major millet contributing 65% of total millet production (FAO, 2020). Fodder sorghum (Sorghum bicolor) is a major forage crop in tropical and subtropical regions due to its high biomass production, adaptability to varied agroclimatic conditions, and tolerance to drought and heat stress (Patel, 2018) [9] . In addition to green fodder production, availability of quality seed is critical for sustaining fodder-based production systems. Seed yield in fodder sorghum is strongly influenced by growing environment and management practices and therefore evaluating its performance under alternative and sustainable cropping systems i essential to ensure consistent seed supply (Singh and Kumar, 2017) [5,12] . Silvopastoral systems integrating multipurpose trees with forage crops have gained importance for improving resource-use efficiency, soil fertility and system sustainability (Nair, 2012) [14] . Gliricidia sepium, a fast growing nitrogen fixing tree, is widely grown in such systems due to its ability to improve soil nutrient status through biomass addition and pruning residues (Santiago, 2016) [11] . However, information on the seed production performance of fodder sorghum grown under Gliricidia sepium based silvopastoral systems is limited. The present study was therefore undertaken to evaluate the seed production performance of fodder sorghum in a Gliricidia sepium based silvopastoral system and to assess its suitability for sustainable seed production.

Materials and Methods Location:

The experiment was conducted on a Gliricidia sepium based silvopasture maintained in degraded wasteland established under All India Co-ordinated Research Project on Agroforestry scheme at the Institute of Animal Nutrition, Tamil Nadu Veterinary and Animal Sciences University, Kattupakkam, Tamil Nadu, India during the year 2020 to study the seed production performance of fodder sorghum grown under Gliricidia sepium based silvopastoral system. The farm is situated at 12.8198 0 N latitude and 80.0352 0 E longitude with an altitude of 52 m above mean sea level. The soil of the experimental site was red soil and having a pH of 6.2. The soil available nitrogen, phosphorus and potassium were 548.0, 4.6 and 190 kg ha -1 , respectively and the organic carbon content was 0.62%. Annual rainfall of the region during the experimental period was 1480 mm and more than 80 per cent was received between August to December. Mean annual maximum and minimum temperature were 32.15 0 C and 25.02 0 C, respectively.

Experimental details: Fodder sorghum variety Co(FS)29 was selected for this experiment. The experiment was laid out in a Randomized Block Design (RBD) replicated four times. The treatments are; Fodder sorghum was established with two methods viz., Line sowing with a spacing of 60 x 15 cm (T 1 ) and Broadcasting (T 2 ). The plot size adopted was 5mx3m. Seed rate of 5kg/ha was used for line sowing and for broadcasting 10 kg/ha was used. Ploughing was done three times to get good tilth, ridges and furrows of 6m long and 60 cm apart were formed and line sowing was done with a spacing of 60 x 15 cm. First weeding on 25-30 days after sowing and depending on the weed flora weeding was done periodically. Irrigation was carried out once in 7days depending upon the soil moisture condition. Seeds were harvested 125 days after sowing and harvested three times in a year. All recommended agronomic practices such as land preparation, fertilizer application, irrigation, weed management and plant protection measures were uniformly followed for all the treatments, except the method of sowing.

Statistical analysis:

The data recorded were subjected to analysis of variance (ANOVA) appropriate for a Randomized Block Design to test the significance of treatment effects. The treatment means were compared using the critical difference (CD) at 5% level of significance. Pictures 1 to 8 depicts the establishment of Fodder sorghum Co(FS)29 to evaluate the seed production performance of fodder sorghum understorey Gliricidia sepium based silvopastoral system.

Results and Discussion

The growth and yield of fodder sorghum Co(FS) 29 grown under a Gliricidia sepium based silvopastoral system were influenced by the type of sowing at different cutting intervals is presented in Table 1 and figure 1. Across all three harvests, line sowing (T 1 ) consistently recorded higher plant height, number of tillers, leaf length, leaf breadth and dry fodder yield compared to broadcasting (T 2 ); however, these differences were statistically non-significant. A progressive reduction in growth parameters was observed with successive harvests, irrespective of sowing method, indicating the effect of repeated cutting and understorey growing conditions. The present findings are in agreement with the findings of Iyanar et al. (2015) [4] . The number of leaves per tiller differed significantly at the first harvest with line sowing producing more leaves than broadcasting, while no significant differences were observed at subsequent harvests. Seed yield was significantly influenced by the type of sowing at all harvests. Line sowing produced significantly higher seed yield than broadcasting at the first harvest (53.30 vs. 35.30 kg ha⁻¹), second harvest (40.10 vs. 27.10 kg ha⁻¹) and third harvests (35.96 vs. 20.83 kg ha⁻¹). The superior performance under line sowing may be attributed to better plant spacing and reduced competition under tree shade. Shattering of seeds to the extent of twenty five per cent in Co(FS)29 was attributed as reason for poor seed yield. The similar results were earlier reported by Manjunath Patil et al., 2024 [6] . Dry fodder yield was numerically higher under line sowing at all harvests, but the differences were non-significant. Overall line sowing (60 × 15 cm) proved more efficient than broadcasting for improving seed yield and maintaining better growth of fodder sorghum under Gliricidia sepium based silvopastoral systems. Irrespective of the harvest the seed yield was significantly (P<0.05) highest in line sowing. There was no significant (P>0.05) variation in all other parameters for all harvests irrespective of treatments adopted. However in the first harvest the number of leaves per tiller was significantly (p<0.05) highest in line sowing.

The growth and yield parameters of fodder sorghum Co(FS) 29 understorey Gliricidia sepium as influenced by cutting intervals irrespective of type of sowing is presented in Table 2 and figure 2. 3.90 b ±0.09 2.17 a ± 0.13 1.98 a ± 0.05 L:S ratio 0.17 b ± 0.00 0.10 a ± 0.00 0.10 a ± 0.00 Seed yield (Kg/ha) 44.30 b ± 4.95 33.60 ab ± 3.77 28.40 a ± 4.07 Dry fodder yield(t/ha) 9.17 b ± 0.35 5.20 a ± 0.19 4.75 a ± 0.12 *Mean of six replications Means bearing alphabetical superscripts within rows differ significantly (p<0.05) NS -Statistically Non significant (p>0.05)

The growth and yield parameters of fodder sorghum Co(FS) 29 grown understorey in Gliricidia sepium, as influenced by cutting intervals irrespective of the type of sowing, showed significant variation (Table 2). The first cutting recorded significantly higher plant height (210.95 cm), number of tillers (8.50), number of leaves per tiller (75.67), leaf length (69.83 cm), leaf breadth (3.90 cm), and leaf-to-stem ratio (0.17) compared to the second and third cuttings, indicating better vegetative growth and forage quality during the initial harvest. This superiority may be attributed to greater availability of assimilates, better nutrient uptake, and less physiological stress during early growth stages, whereas successive cuttings likely reduced carbohydrate reserves and regenerative capacity of the plants. Yield parameters followed a similar trend, with the highest seed yield (44.30 kg ha⁻¹) and dry fodder yield (9.17 t ha⁻¹) recorded at the first cutting, which were significantly higher than the third cutting and comparable to the second cutting. The progressive decline in growth and yield with later cuttings could be due to reduced photosynthetic area, shading effects of Gliricidia sepium, and depletion of soil moisture and nutrients over time. Overall, the results demonstrate that the first cutting interval is more favorable for maximizing growth, fodder yield and forage quality of fodder sorghum Co(FS) 29 under Gliricidia sepium irrespective of sowing method. The seed yield and fodder yield of fodder sorghum Co(FS)9 as influenced by treatments and harvest intervals is presented in Table 3. Line sowing at 60 × 15 cm (T₁) recorded higher seed and fodder yields at all harvests compared to broadcasting (T₂), resulting in greater total seed yield (129.4 kg ha⁻¹) and dry fodder yield (19.9 t ha⁻¹). In both treatments, yields were highest at the first harvest and declined in subsequent harvests. The superior performance of line sowing may be attributed to better plant spacing, efficient resource utilization, and reduced competition, while the reduction in yield with successive harvests could be due to depletion of plant reserves and reduced regenerative capacity after repeated cutting. These results corroborate the findings of Patil et al., 2024 [10] , who reported that management practices viz., optimizing sowing and nutrient practices influences the seed yield in perennial fodder sorghum.

The net economics of fodder seed production as influenced by sowing methods are presented in Thus, the results clearly indicate that line sowing is economically superior to broadcasting for fodder seed production.

Conclusion

The present investigation clearly demonstrates that fodder sorghum Co(FS)29 can be successfully grown for seed production under a Gliricidia sepium based silvopastoral system in degraded wastelands. Among the sowing methods evaluated, line sowing at 60 × 15 cm proved superior to broadcasting by significantly enhancing seed yield across all harvests and providing better economic returns, while maintaining comparable growth and fodder yield. Irrespective of sowing method, the first cutting was most favorable for achieving higher growth, forage quality, seed yield and dry fodder yield, with a progressive decline observed in subsequent cuttings. The integration of fodder sorghum with Gliricidia sepium thus offers a sustainable option for augmenting forage seed availability while improving land productivity. Adoption of line sowing under silvopastoral systems can therefore be recommended for enhancing fodder seed production and farm profitability in similar agroclimatic conditions.

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