Effect of Nutrient Levels on Growth, Yield and Economics of Dolichos Bean (Dolichos lablab L.) in Northern Dry Zone of Karnataka, India

Dolichos bean (Dolichos lablab L.) is one of the most precious legume crop grown both for tender pods and dry seeds occupies unique position both as vegetable and pulse purpose in the tropics. It has many nutritional benefits and it is the best source of digestible vegetable protein (20-25%) required for human health, because of this, this crop is considered as a poor man’s meat (Joshi and Rahevar, 2015). Unlike other legumes, it has ability to fix nitrogen into soil thereby improving soil fertility and crop yields in an economic and environment friendly manner. But application of nitrogen especially in early stage is highly responsive and not only improves the yield and yield components of dolichos bean but also influence the biological nitrogen fixation (Sammauria et al., 2009). Likewise, application of phosphorus serves dual purpose in legume by increasing the yield of green pods of current as well as succeeding crop of the dolichos bean (Turuko and Mohammed, 2014). Potassium also plays an important role in promotion of enzyme activity and enhances the translocation of assimilates thereby increases the plant growth and yield of dolichos bean (Devlin and Witham, 1986). The growth and yield of crop are largely influenced by application of judicious and adequate fertilizer doses but basically, the farmer adopts only those improved practices which are more paying and easily workable (Shahid et al., 2015). Dolichos bean as a vegetable is growing in a limited area of Karnataka and also does not have a separate recommended package of practices, however, farmers are growing this crop by adopting the recommended fertilizers dose used for field type of dolichos bean. Therefore, the present study was undertaken to find out the optimum dose of nitrogen, phosphorus and potassium for profitable production of vegetable type dolichos bean crop by realizing higher pod yield in northern transition zone of Karnataka.

The experiment was carried out experimental plot of Department of Vegetable Science, Kittur Rani Channamma College of Horticulture, Arabhavi, Belgaum district during rabi 2016 and 2017 on dolichos bean. Soil of the experimental site was medium black soil with fairly uniform topography. The soil was low in available nitrogen (228.05 kg/ha), high in phosphorus (68.29 kg/ha) and medium in available potassium (266.85 kg/ha). The experiment was laid out in the factorial randomized complete block design. The NPK fertilizers were applied in different levels nitrogen (0 and 25 kg/ha), phosphorus (0, 50 and 75 kg/ha) and potassium (0, 25 and 50 kg/ha) in eighteen different combinations with three replications.  Full dose of fertilizers (nitrogen, phosphorus and potassium) in the form of urea, single super phosphate and muriate of potash, respectively were applied to soil before seed sowing as per the treatment. Dolichos bean seeds (var. Arka Amogh) were used for sowing at the seed rate of 20 kg/ha. Two seeds per pit were sown in the rows at a depth of 1.5 to 2 cm by dibbling method at a row spacing of 45 cm and plant to plant spacing of 15 cm. Five healthy plants other than border plants selected randomly were tagged from the net plot area of each treatment for recording various observations and the data collected were analyzed statistically following the procedure described by Panse and Sukhatme (1978). The cost of cultivation and gross returns per hectare were calculated. The benefit cost ratio was worked out using the formula:

Effect of nutrient levels on growth parameters of dolichos bean
 
The data presented in Table 1 revealed significant influence of different levels of nitrogen (N), phosphorus (P), potassium (K) and their interactions on growth parameters  like plant height, number of branches (primary and secondary), leaf area at various growth stages, plant dry matter production at harvest due to fertilizer levels (Table 1). Plant height is an important vegetative trait for biomass production. Significantly taller plants (89.65 cm) were obtained from 25 kg N/ha (N₂ level) than without nitrogen (N₁ level) application in pooled analysis. Similarly, plant receiving higher dose of phosphorus (75 kg P₂O₅/ha) and potassium (50 kg K₂O/ha) gave significantly taller plants (91.69 cm and 88.63 cm) as compared to lower levels in pooled analysis.  Similar trend was also observed in 2016-17 and 2017-18 experimental years. Among the different interactions of NPK (N-P₂O₅-K₂O), the plant height was significantly maximum (98.13, 98.57 and 98.35 cm) in 25-75-50 kg N-P₂O₅-K₂O/ha (T₁₈) which was onpar with T₁₇ in 2016-17, 2017-18 and in pooled data respectively. On pooled basis, plant height was significantly varied from 90.95 cm in recommended fertilizer level of 25-50-25 kg N-P₂O₅-K₂O/ha (T₁₄) to 98.35 cm in highest fertilizer level of 25-75-50 kg N-P₂O₅-K₂O/ha. The marked variations amongst the indivisual NPK and their interaction levels were also noticed for production of primary and secondary branches during both the years. The individual effect of NPK was significantly varied for production of primary and secondary branches and recorded more in N₂ (8.14 and 6.17), P₃ (8.73 and 6.66) and K₃ (8.00 and 6.08) over lower levels in pooled data, respectively. Similar trend was also noticed in 2016-17 and 2017-18 successive growing seasons. Among the interaction levels, pooled data showed that maximum number of primary (9.33) and secondary (7.17) branches were recorded at highest fertilizer level of 25-75-50 kg N-P₂O₅-K₂O/ha compared to the recommended fertilizer level (25-50-25 kg N-P₂O₅-K₂O/ha) at harvest but it was onpar with 25-75-25 kg N-P₂O₅-K₂O/ha (T₁₇). Similar trend was also noticed in 2016-17 and 2017-18 successive growing seasons. The results on plant height and number of branches (primary and secondary) were also obtained by Sammauria et al., (2009) in cluster bean.
 

        
The large size leaves receive more sunlight for photosynthesis as compared to smaller leaves. Leaf area responded significantly to different levels of NPK and their interaction in all the growth stages. In pooled data analysis, significantly maximum leaf area per plant (331.98, 346.76 and 329.23 cm²) was registered with the higher nitrogen (25 kg N/ha), phosphorus (75 kg P₂O₅/ha) and potassium (50 kg K/ha) fertilization over other levels.  The similar trend was also noticed in both the experimental years (2016-17 and 2017-18). Among interaction levels, on pooled basis, higher fertilizer dose of 25-75-50 kg N-P₂O₅-K₂O/ha  recorded significantly maximum leaf area (371.62 cm²) followed by T₁₇ (362.80 cm²) and T₁₆ (356.63 cm²) compared to other treatments. In first (2016-17) and second (2017-18) season of experiments, the result trend was same as followed in pooled data.  Maximum leaf area with higher fertilizer levels was also reported by Veeresh (2003) in French bean. The significant increase in growth parameters noticed under higher fertilizer dose was attributed to better utilization of plant nutrients resulted in the luxuriant crop growth through enhanced cell division, elongation and differentiation as compared to lower fertilizer level. Similar results regarding growth parameters of dolichos bean also confirmed by Shrikanth et al., (2008). Indivisual effect of NPK fertilization had significant influence on dry matter production per plant during both the experimental year as well as in pooled data. Higher nitrogen (25 kg/ha), phosphorus (75 kg/ha) and potassium (50 kg/ha) fertilization produced significantly higher dry matter content (24.54, 27.65 and 23.99 g) over lower levels. The similar trend was also noticed in both the experimental years (2016-17 and 2017-18). The NPK interaction has also promotive effect on dry biomass and recorded maximum dry weight of plant (35.97 g) in plants supplied with higher dose of fertilizer (25-75-50 kg/ha) followed by T₁₇ (33.77 g) and T₁₆ (29.67 g) which showed 11 (13.27 g), 9 (11.07 g) and 3 (4.1 g) per cent higher over recommended fertilizer level of 25-50-25 kg N-P₂O₅-K₂O/ha (22.70 g). The interaction effects during 2016-17 and 2017-18 experimental years also followed similar trend as that of pooled analysis. The higher dry matter production with increase fertilizer dose was mainly due to maximum green biomass and its accumulation in various plant parts.  Similar results have also been noticed by Shrikanth et al., (2008) who observed significantly higher dry matter in higher fertilizer level of 33-67-33 kg N-P₂O₅-K₂O/ha.
 
Effect of nutrient levels on flowering and yield components of dolichos bean
 
The indivisual effect of NPK and their interaction were significantly varied for flowering and yield parameters during first, second season and in pooled analysis (Table 2). Early onsets of reproductive phase indicate earliness. Nitrogen application prolonged the flowering period of dolichos bean. Thus delayed flowering viz. fifty per cent flowing (41.41 days) and physiological maturity (75.06) were also observed due to 25 kg N application/ ha. Early days to fifty per cent flowing (37.36 and 40.33) and maximum days to crop maturity (75.64 and 75.03) were noticed in higher levels of phosphorus (75 kg P₂O₅/ha) and potassium (50 kg K₂O/ha) over lower levels. The similar trend was also noticed in both the experimental years (2016-17 and 2017-18). Significantly minimum days to 50 per cent flowering (38.67, 39.00 and 38.83) was recorded in recommend fertilizer dose (25-50-25 kg/ha) whereas maximum days to crop maturity (77.33, 77.00 and 77.17) was recorded in higher fertilizer dose of 25-75-50 kg/ha (T₁₈) followed by T₁₇ and T₉ in 2016-17, 2017-18 and in pooled data respectively, which confirmed the findings of Shrikanth et al., (2008).
        
The plant yield is a dependent variable, which depends upon all other growth and yield contributing traits. The higher pod yield with higher fertilizer dose was due to increase in number of pods per plant (Achakzai and Bangulzai, 2006) which was significantly influenced by indivisual and interaction of NPK levels during both the growing season (2016-17 and 2017-18) of experiment (Table 2). Pooled analysis of data indicate, significantly maximum number of pods per plant (134.18, 142.58 and 134.53) was observed in higher levels of nitrogen (25 kg N/ha), phosphorus (75 kg P₂O₅/ha) and potassium (50 kg K₂O/ha) compared to lower levels. Similar observations were also made during both the years of the study. In the present study, on pooled basis, significantly higher number of pods per plant (148.78) was recorded in 25-75-50 kg/ha (T₁₈) followed by T₁₇ (146.20) and T₉ (143.35), which showed maximum improvement of 12.86 (11%), 10.28 (9%) and 7.43 (6%) number of pods per plant compare to recommended dose of 25-50-25 kg N-P₂O₅-K₂O/ha (135.92). These results can be due to better utilization of NPK which enhanced photosynthetic activity, accumulation and translocation of assimilates from source to sink resulting in improved yield attributing characters in higher dose of fertilizers. These results are confirmed with the findings of Palankar and Malabasari (2014) in cluster bean.
 

 
Effect of nutrient levels on pod yield of dolichos bean
 
Pod yield of dolichos bean var. Arka Amogh significantly influenced by indivisual NPK and their interaction levels in 2016-17, 2017-18 growing seasons and pooled analysis presented in Table 2. On pooled basis, the higher level of nitrogen (25 kg N/ha), phosphorus (75 kg P₂O₅/ha) and potassium (50 kg K₂O/ha) produced significantly higher pod yield per plant (139.57, 154.31 and 141.21 g) and pod yield per hectare (162.32 q, 184.14 q and 164.75 q) compared to lower levels, respectively. Similar observations were also noticed during 2016-17 and 2017-18 growing seasons. Among the interaction levels, on pooled basis, significantly higher fertilizer dose of 25-75-50 kg N-P₂O₅-K₂O/ha (T₁₈) produced more pod yield per plant (163.95 g) followed by T₁₇ and T₉ treatment combinations which showed maximum improvement of 20.78 g (17 %) over recommended fertilizer level T₁₄ (25-50-25 kg N-P₂O₅-K₂O/ha). Similarly, T₁₈ also recorded significantly higher pod yield per plant but it was onpar with T₁₇ (161.50 g) in first season (2016-17) whereas in second season (2017-18) the similar trend was observed. These results may be due to the fact that the dolichos bean responded well to the enhanced doses of fertilizers. These results are in consonance with the findings of Palankar and Malabasari (2014) in cluster bean. Amongst the NPK interaction levels, in pooled data, maximum pod yield per hectare was recorded at T₁₈ (198.44 q) followed by T₁₇ (193.43q) and T₉ (190.20 q). The result trend was same in first (2016-17) and second (2017-18) season of experiments. Maximum pod yield per hectare was recorded at T₁₈ which showed maximum improvement of 20.78 g (17%) and 30.79 q (26%) over recommended fertilizer level (25-50-25 kg N-P₂O₅-K₂O/ha). This might be due to increased performance of growth parameters and also complementary effect of optimum combinations of nitrogen, phosphorus and potassium levels. These results confirmed the finding of Shrikanth et al., (2008) in dolichos bean.
 
Effect of nutrient levels on economics of dolichos bean
 
Economic feasibility of the fertilizer practices should be an essential element of studies aimed at improving crop productivity (Shahid et al., 2015). All the fertilizer levels were found profitable over control indicating that the use of fertilizer in judicious amounts will always remain a profitable proposition for the dolichos bean growers. The higher estimated value of gross income obtained during 2016-17, 2017-18 growing season and in pooled data was significantly varied due to NPK interactions levels (Table 3). In pooled data, significantly maximum gross income (Rs. 396889/ha) obtained from higher fertilizer dose 25-75-50 kg N-P₂O₅-K₂O/ha (T₁₈) followed by 25-75-25 kg N-P₂O₅-K₂O/ha (T₁₇) and 0-75-50 kg N-P₂O₅-K₂O/ha (T₉) whereas, in 2016-17, maximum gross income was recorded from T₁₈ (Rs. 398420/ha) which was statistically onpar with T₁₇. Regarding gross income, similar trend was also noticed in 2017-18 growing seasons as followed in pooled data. This was due to higher pod yield recorded with these levels of nutrients.
        
The total cost of cultivation of dolichos bean included treatment cost and common expenditure incurred for cultivation during the year 2016-17 and 2017-18. In the present study, the cost of cultivation in different treatments differed significantly mainly for the variation in cost of nutrient (NPK) during both the years of investigation (Table 3). Among all the treatment combinations, higher fertilizer dose of 25-75-50 kg N-P₂O₅-K₂O/ha (T₁₈) was recorded higher cost of cultivation (Rs. 75292/ha) followed by T₉ and T₁₇. However, the lowest cultivation cost was registered with control (T₁) during both the years (2016-17 and 2017-18) of cultivation. Interaction levels of NPK showed significant impact on net returns in dolichos bean cultivation during 2016-17, 2017-18 and in pooled data. Significantly maximum net profit (Rs. 321,597/ha) was recorded from higher dose (T₁₈) of fertilizer application which was followed by T₁₇ (Rs. 312,048/ha) over rest of the treatment combinations whereas, in 2016-17, maximum net profit was obtained from T₁₈ (Rs. 323,128/ha) which was statistically onpar with T₁₇. Simlar trend was also noticed during 2017-18 growing season. The marked variations in interaction effect of NPK levels were noticed in relation to benefit cost ratio of dolichos bean cultivation during both the years and in pooled data. Pooled analysis data indicated that, T₁₈ (25-75-50 kg N-P₂O₅-K₂O/ha) recorded higher benefit: cost ratio (5.27) which was statistically onpar with T₁₇. However, lower benefit: cost ratio (3.31) was recorded in control (T₁). Similar trend was also noticed during 2016-17 and 2017-18 growing seasons. Evidently, all the fertilizer levels were found profitable over control, which received no fertilizers, indicating that the use of fertilizer in judicious quantity will always remain a profitable proposition for the dolichos bean growers and it shown responds well to the application of higher fertilizer dose over recommended fertilizer dose. Similar result also obtained by Thirumalai and Khalak (1993), Shahid et al., (2015) and Shubhashree et al., (2011) in French bean.
 

Dolichos bean responds well to the application of higher fertilizer dose over recommended fertilizer dose. However, from the combined data of both the consecutive years, it can be concluded that for profitable cultivation of vegetable type dolichos bean var. ‘Arka Amogh’, fertilizers must be supplemented at the rate of 25-75-25 kg N-P₂O₅-K₂O/ha which gave higher green pod yield and profitability against recommended fertilizer level (25-50-25 kg N-P₂O₅-K₂O/ha), at Arabhavi condition under Belgaum district of Karnataka.