Sugarcane is an important commercial cash crop and plays vital role in Indian agriculture. It ranks second after Brazil both in area and production among sugar producing countries. It is grown in 4.5 per cent of the total cropped area of the country. Ratoon is unique phenomenon in the sense that a number of succeeding sugarcane crops will be raised from a single planting which is an integral component of sugarcane production system. In India more than 50 to 55 per cent of sugarcane acreage is occupied by ratoons, which are often poor yielders than the plant cane due to non-adoption of improved agricultural technologies. However, its contribution to the total cane production is about 30 per cent. Ratooning in sugarcane is economical for the farming community as the production cost is lowered by 25 – 35 per cent over plant crop in addition to saving on cost of seed material. But the productivity is 10 to 30 per cent less than the plant crop of sugarcane. A ratoon crop matures prior to plant crop ensuring early supply of cane to mills. Under similar conditions sugarcane ratoon have a supplementary advantage of better juice quality and sugar recovery more than plant crop of same variety [1].

            Fertilizer is one of the most important agricultural inputs for increasing the crop production. Soil testing is now accepted as a procedure for the recommendation of fertilizer doses for various crops. But soil testing would become a useful tool only when it is based on intimate knowledge of soil-crop-variety-fertilizer-climate management interaction for a given situation [2]. In this regard targeted yield approach has been found to be beneficial which recommends balanced fertilization considering available nutrient status in the soil and the crop needs. Excessive and indiscriminate use of inorganic fertilizers creates imbalance of nutrition causing decline in productivity and simultaneously increase the cost of production per ton of cane. Application of adequate inorganic fertilizers on soil test basis will certainly be helpful for increasing productivity of sugarcane with better soil health [3-5] reported the superiority of the target yield concept over other practices for different crops as it gave higher yields, net benefit and optimal economic returns. The present investigation was undertaken to assess the feasibility of fertilizer prescription equations of target yield approach in ratoon sugarcane.

Hence, the present study was carried out for sugarcane on Vertisols of Nizamabad (Telangana) which is neutral to slightly alkaline in nature. Extrapolation of the results emanated from the study is possible if it is test verified at farmer’s holdings. Therefore, to enhance the production of sugarcane ratoon and to sustain soil health, verification of suitable fertilizer prescription model is highly essential.

Materials and Methods

Field experiments were conducted at Regional Sugarcane and Rice Research, Rudrur during during Eksali 2017-18 to Eksali 2019-20. The fertilizer prescription equations developed for desired yield target of sugarcane ratoon are furnished below.

STCR Equation for sugarcane ratoon crop

FN = 12.53T-4.66SN

FP₂O₅ = 1.82T-3.24SP

F K₂O = 4.48T-0.97SK

Where, FN, FP₂O₅ and FK₂O are fertilizer N, P₂O and K₂O in kg ha^-1 respectively. T is the yield targeted in t ha^-1; SN, SP and SK are soil available N, P and K in kgha^-1 respectively. The treatments include farmer’s fertiliser practice, RDF and soil test crop response (STCR) based fertilizer dose for a yield target of 90 t ha^-1.

Initial soil samples were collected in each location and analysed for alkaline KMnO₄-N [6] Olsen-P [7] and NH4OAc-K [8].Initial determination of native fertility revealed that, soils were neutral in reaction to non-saline in nature. Available N, P and K were low, medium to high and medium to high in status ranging from 189 to 201, 28 to 34 and 308 to 342 kg ha^-1, respectively (Table 1). The test crop sugarcane variety 83 R 186 was raised during Eksali 2017-18 to Eksali 2019-20. BCR (B:Cratio) was worked out based on the standard procedure [9]. The cultivation practices were carried out periodically and the cane yield was recorded at harvest.

            The available status of nutrients was used to compute fertiliser doses for sugarcane through adjustment equations using basic data that had earlier been generated from fertility gradient field experiments for sugarcane. The detailed procedure has been described by [10]. The range of N, P₂O₅ and K₂O application rates under different treatments indicated that, N, P₂O₅ and K₂O recommendations by farmers practice were higher than STCR recommendations. Fertilizer recommendations for sugarcane under different treatments over three years indicated that, farmers practice of N, P₂O₅ and K₂O recommendations are342, 136 and 110kg ha^-1, respectively where as STCR practice of N, P₂O₅ and K₂O recommendations ranged from 233, 69 and 91 kg ha^-1, respectively (Table 1). Recommended dose of fertilizer application for sugarcane ratoon crop in Telangana region is 233-69-91 kg N- P₂O₅-K₂O ha^-1.

Table 1: Fertilizer recommendations for sugarcane ratoon under different treatments (Pooled over three years)

Results and Discussion

            The results showed that, against the sugarcane yield target of 90t ha^-1, the cane yield in STCR recommendation is 90 t ha^-1 (Table 2).With respect to farmer’s practice of fertiliser recommendations, the yield is 88 t ha^-1 where as in RDF; the yield is 90 t ha^-1.The mean yield obtained in soil test based targeted yield for 90 t ha^-1 (90 t ha^-1) was more or less similar with that of farmer practice of fertilizer recommendations (88 t ha^-1). The results of the experiment revealed that, the per cent achievement of the targeted yield was within ±5% variation proving the validity of the equations for prescribing fertilizer doses for sugarcane ratoon crop. Similar results were reported in sugarcane ratoon by [11] at SRS, Vuyyur, Krishna district, Andhra Pradesh.

Table 2: Cane yield and Benefit Cost Ratio of sugarcane ratoon under different treatments (Pooled over three years)

Validated STCR equation for hybrid maize and reported that, STCR based fertiliser recommendations with the targeted yield have been achieved within +/- 10 per cent variation proving the validity of the equations [12]. Similar results were reported by [13] for beetroot, [14] for pearl millet, [15] for rice, [16] for Brinjal. According to [17], if the targeted yield was achieved within ± 10 per cent variation, then the equations are found to be valid. The results of the validation experiment on soybean clearly indicated that the per cent achievement was above 10 per cent (72-91 %) variation at all the locations for validation was not achieved the targeted yield of soybean crop [18-19].

The benefit cost ratio of the treatments was estimated using the cost of input and value of output. Economics of fertiliser application based on targeted concept gave benefit cost ratio of 2.47 (Table 2). The corresponding value for farmers fertiliser practice and RDF is 2.35 and 2.40, respectively. The results are confirming that, the higher benefit cost ratio recorded through targeted yield approach comparison to farmers practice of fertiliser recommendations and RDF. The treatment of targeted yield found most economic treatment as compare to farmer practices and general recommendation reported by [15].

The fertiliser prescription equation developed for sugarcane ratoon crop has succeeded to achieve the target yield of 90 t ha^-1 and found suitable to harvest the targeted yield of sugarcane.  A net saving of  N, P₂O₅ and K₂O fertilizers from current recommended dose by 62, 31 kg and 29 kg ha^-1, respectively and saving of cost of fertilizers applied per hectare to the extent of Rs.3,247/-.

Fig.1. Overall view of the experimental site at Karegam village

Conclusion

The STCR equation (FN = 12.53T-4.66SN; FP₂O₅ = 1.82T-3.24SP; FK₂O = 4.48T-0.97SK) developed for sugarcane ratoon crop can be recommended for Vertisols of the Northern Telangana Zone for achieving a yield target of 90 t ha^-1 and it can be extrapolated to other agro-climatic zones of Telangana on similar and allied soil types.

References

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