Growth, yield attributes and yield
The pooled data regarding ancillary and yield attributing characters of Pigeon pea (Table 1) revealed that, drip fertigation had significantly influenced plant height, number of root nodules at 60 DAS, dry matter weight per plant, number of pods per plant and grain weight per plant. The highest values for all these characters were recorded with application of 125% N and 100% P and K through drip fertigation, closely followed by 100% NPK and 75% N and 100% P and K, However lowest values for all the growth and yield attributing characters were observed in furrow irrigation with conventional method of fertilizer application (T
1) and 100% NPK as basal with drip irrigation (T
2). The treatment T
6 i.e. drip fertigation with 125% N + 100% P+ 100% K in five splits was found at par with 100% NPK ha
-1 in respect of all the growth and yield characters.Increase in the levels of N, P and K through fertigation increases the plant height, number of branches, dry matter weight per plant and root nodules per plant at 60 DAS which might be due to enhanced availability and uptake of nutrients leading to enhanced photosynthesis, expansion of leaves and translocation of nutrients to the reproductive parts as compared to soil application method
Singh and Yadav (2008) and
Manikandan et al., (2015) also reported the beneficial effect of higher level of N, P and K fertigation on growth and yield attributes which indicated that pigeon pea required more nutrients for enhancing the growth and yield attributes Vanishree
et al. (2019) also reported that higher number of pods,seed weight g plant
-1, stalk and seed yields was recorded with drip fertigation of recommended N and P
2O
5 in five splits using water soluble fertilizers (WSF) compared to other drip fertigation of water soluble and normal fertilizers at different levels of splits.
Application of higher level of fertigation
i.e. 125:100:100 per cent recommended dose of NPK in five splits recorded maximum number of pods plant (301) and grain weight per plant (152.71 g) and established its significance over 100 per cent recommended dose of N,P and K in furrow irrigation and drip irrigation through soil application and all other lower level of fertigation. The substantial increase in number of pods per plant and grain weight per plant due to higher levels of fertigation than lower level and conventional fertilizer application method was associated with the improvement in various growth attributes
viz. plant height, number of branches, functional leaves, leaf area, dry matter accumulation per plant and its subsequent translocations to sink. The cumulative effect of these finally improved the number of pods per plant and grain weight per plant, because the ability of pigeon pea crop to produce and support more number of pods depends on dry matter accumulation and its translocation to sink. The increase in more number of pods per plant and grain weight per plant under higher level of fertigation might be due to enhanced availability and uptake of nutrients to enhance photosynthesis, expansion of leaves and translocation of nutrients to reproductive parts as compared to lower rate of N, P and K given through fertigation and over conventional soil application of fertilizers. Furrow irrigation with 100% NPK (T
1) recorded significantly lower number of pods per plant and grain weight per plant than all other treatments may be due to leaching of nutrients and moisture variations between two successive irrigationswith lower uptake of nutrients. Similar advantage of higher level of fertigation of nutrients in improving the number of pods per plant and grain weight per plant were reported earlier by
Kumar and Kushwaha (2006) and
Manikandan and Sivasubramaniam (2014).
Grain yield and harvest index
Pooled data of three years indicated in Table 2 revealed that, drip fertigation at 125 per cent recommended N, 100 per cent P and 100 per cent K ha
-1 had recorded significantly higher Pigeon pea grain yield in the individual years as well as in pooled (4053 Kg ha
-1) of three years and followed by drip fertigation at 100 per cent RDNPK ha
-1 which registered next higher Pigeon pea grain yield of 3913 kg ha
-1. There was a significant response to fertigation of all the nutrients through drip in five splits than furrow and drip irrigation coupled with conventional method of fertilizer application. The lowest pooled grain yield was recorded at T
1 (Furrow irrigation with 100 % NPK as soil application) which might be due to losses of fertilizers through leaching and volatilization in conventional method of fertilizer application. Drip fertigation at 75 per cent recommended dose of NPK ha
-1 registered significantly comparable yield with 100 per cent recommended dose of NPK ha
-1 applied through soil by conventional method during 2016-17, 2017-18 and 2018-19 years of study and pooled of three years also showed the similar trend indicating 25 per cent fertilizer saving through fertigation when compared to conventional method of fertilizer application with drip irrigation. The saving of fertilizers might be due to reduction in losses of nutrients through volatilization and leaching and better movement of nutrients under drip fertigation as against soil application of fertilizers. Drip fertigation at higher level of 125:100:100 per cent NPK ha
-1 fertigation recorded 52.67 per cent and 29.06 per cent increase in yield over conventional soil application with furrow irrigation and conventional soil application with drip irrigation respectively over the pooled of three years. Better crop growth at higher fertigation levels influenced the yield attributes favourably. The increase in yield might be due to better proportion of air-soil-water which was maintained throughout the life period of crop in drip fertigation compared to surface irrigation with conventional method of soil application of fertilizers. Increased nutrients availability and absorption by the crop at the optimum moisture supply coupled with frequent and higher nutrient supply by fertigation and consequent better formation and translocation of assimilates from source to sink might have increased seed yield under fertigation. The results are in conformity with the findings of
Praharaj and Kumar (2012),
Chandrashekhar et al. (2014);
Praharaj et al., (2016); Vimalendran and Latha (2016).
The harvest index was significantly influenced due to fertigation over conventional method of fertilizer application. Highest pooled harvest index of 36.62 was registered in the treatment of drip fertigation with 100% N + 75% P+75% K in five splits followed by 125% N + 75% P+ 75% K in five splits. The results are in conformity with the results of
Singh and Singh (2012) and
Chandrashekhar et al. (2014) who reported that harvest index increased with increase in the level of fertigation indicating efficient utilization of the biomass for conservation in grain yield.
Water use efficiency and nutrient use efficiency
Water use efficiency is important tool to assess the productivity of crop per unit of water utilized. In pooled data of WUE and NUE (Table 3) , it was observed that, highest water use efficiency of 7.85 Kg ha
-1 mm was recorded with drip fertigation at higher level of 125:100:100 per cent NPK ha
-1 followed by water use efficiency of 7.59 Kg ha
-1 mm in fertigation level of 100:100:100 per cent NPK ha
-1. Lowest value of water use efficiency (3.11) was noticed where furrow irrigation was given with conventional soil application of fertilizers. This might be due to more water consumed in furrow irrigation with less yield compared to all the drip and fertigation treatments. Nitrogen, phosphoric acid and potassium applied through drip irrigation had distinct bearing as evident from higher WUE with higher level of recommended dose of NPK. Markedly higher WUE was recorded with higher level of fertigation than lower level, because of adequate and timely availability of water and nutrients and their positive interaction might have simulated the early growth and increased the yield to record higher WUE under drip fertigation with higher levels compared to soil application of fertilizers.
Praharaj et al., (2014), Vimalendran and Latha (2014),
Praharaj et al., (2016) also reported the similar finding of increasing water use efficiency with increasing level of fertigation.
Maximum nutrient use efficiency was observed in all the treatments where fertilizer was applied as fertigation in five splits as compared to soil application of fertilizer in furrow and drip irrigation.The nutrient use efficiency was considerably increased in drip fertigation compared to soil application of N, P and K fertilizers. This could be attributed to regular application of N,P and K (as high as five splits in drip fertigation) combined with irrigation water in the active root zone of the crop and their interaction in even N distribution in the soil with minimum leaching of nutrients away from the root zone. These results are in accordance with the findings of
Hassan et al., (2010), Praharaj et al., (2014).
Soil moisture content
The soil moisture data indicated in Table 2 revealed that, adequate soil moisture availability ensures successful Pigeon pea production under drip irrigation. The soil moisture data indicated that, in drip fertigation system below dripper point (0-15 cm), the moisture content at 24 hrs. after drip irrigation showed higher soil moisture content in the top layer and progressively decline vertically in the bottom layer (15-30 cm). The results of present investigation indicated that uniform soil moisture distribution due to increased frequency of irrigation at once in two days led to higher and constant moisture availability nearer to field capacity. Similar results in respect of soil moisture distribution in cotton have been reported by
Suganya et al., (2007) and
Gokila (2012) in drip irrigation. At 60 DAS, 120 DAS and at 150 DAS, soil moisture in all the fertigation treatment was found higher compared to the furrow irrigation. In all fertigation treatments, the moisture availability was at par due to equal application of the water in all the fertigation treatments.
Economics
Fertigation at 125 per cent recommended dose of N 100 per cent P and 100 per cent K registered the maximum GMR (Rs 226807 ha
-1) and NMR (Rs176604 ha
-1) when pooled over three years being comparable with values of 100 per cent fertigation of N,P and K. (Table 3).The higher level of 125 per cent fertigation of recommended dose of NPK ha
-1 registered 51.98 per cent increase in NMR than 100 per cent soil application of N,P and K through conventional method with furrow irrigation. The similar trend of B:C ratio as observed in individual year of 2016-17, 2017-18 and 2018-19 were also observed in pooled data of three years. The data presented in Table 3 indicated that split application of N , P and K fertilizers also improved the economic efficiency (net returns per day) in Pigeon pea and higher economic efficiency (883 Rs day
-1ha
-1 ) was noticed with higher level of 125 per cent N with 100 per cent P and K (T
6) followed by T
7 i.e. DF with 100% N + 100% P+ 100% K in five splits .Similar results were reported by
Singh (2012);
Praharaj and Kumar (2012);
Praharaj et al., (2014).