Application of 60 kg phosphorus/ha although recorded maximum plant height but was at par with 40 kg phosphorus/ha and both recorded significantly higher plant height than 20 kg phosphorus/ha. Similarly plant height recorded among 30 and 20 kg sulphur/ha being at par with and both recorded significantly higher plant height over 10 kg sulphur/ha. Both phosphorus and sulphur levels recorded significantly higher plant height over control (Table 1). Plant dry matter and crop growth rate increased significantly higher values at 60 kg phosphorus/ha. However, plant dry matter and crop growth rate increased significantly up to 20 kg sulphur/ha, further increase in sulphur levels fail to produce significant effect. Phosphorus and sulphur levels recorded significantly higher values of these indices than control. Higher values of these growth parameter on higher phosphorus and sulphur levels might be due to phosphorus estimates initial root improvement and growth, thus help in cell division and elongation. It also enhanced root proliferation and their development thereby enhancing uptake of nutrients and water from soil resulting in better plant growth of the plant. Similar findings were also noticed by Kumawat et al., (2014)
and Gajera et al., (2014).
Sulphur helps to increase enzymatic activity of plant which accelerate the metabolic process result in great plant vigor, resulting more production of photosynthates and their accumulation in plants system these ultimately increase the growth indices. This similar result was recorded by Kumawat et al., (2014).
Table 1: Effect of phosphorus and sulphur levels on plant height, plant dry matter and crop growth rate.
Phosphorus and sulphur levels recorded significantly higher number of pods/plant, pod length, grains/pod and test weight than control (Table 2). Application of 60 and 40 kg phosphorus was found at par with respect to number of pods/plant, pod length, grains/pod and test weight and both recorded significantly higher values than 20 kg phosphorus/ha. Similarly, these indices recorded at 30 and 20 kg sulphur being at par and both recorded significantly higher values of these parameter than 10 kg sulphur/ha. This might be because of raised to higher nutrient absorb and their move which had suitable effect on rate of photosynthesis and production of photosynthates. Efficient portioning of accumulated photosynthates, in turn contribute towards better development of yield indices. These results are supported by Singh et al., (2017b)
and Das (2017)
also recorded the similar result. Sulphur also increase the vegetative growth of plant through the synthesis and activation of many enzyme it also increased the photosynthesis and provide more photosynthates from source of sink resulting favorable increase in no. of pods per plant, length of pod, no. of grain per pod, 100 seed weight. The similar finding was recorded by Ram et al., (2013).
Grain and straw yield
Table 2: Effect of phosphorus and sulphur levels on pods per plant, pod length, grains per pod and test weight.
Phosphorus and sulphur levels significantly enhanced the grain and straw yield of summer greengram than control (Table 3). Application of 60 kg phosphorus/ha although produced higher grain and straw yields (914 and 1946 kg/ha, respectively) but was found at par with 40 kg phosphorus/ha (880 and 1882 kg/ha, respectively) and both recorded significantly higher grain and straw yield than 20 kg phosphorus/ha. Application of 30 kg sulphur/ha although produced higher grain and straw yields (920 and 1933 kg/ha, respectively) but was found at par with 20 kg sulphur/ha (879 and 1886 kg/ha, respectively) and both recorded significantly higher grain and straw yield than 10 kg sulphur/ha. Higher grain and straw yields at higher phosphorus and sulphur level might be due to the availability of plant nutrients in adequate proportion and in balanced quantity to the crop plant lead to improved crop growth and better expression of yield induced when consequently reflected to grain and stover yields. These results are supported by Das (2017)
and Singh et al., (2019c).
Sulphur is essential part in synchronize metabolic or enzymatic activity as well as respiration, photosynthesis or rhizobium legume cooperative nitrogen activity, these processes help to increase grain and straw, besides it is essential part of energy transformation, operate many enzymes and important in carbohydrate metabolism. Similar finding was recorded by Patel et al., (2013a), Singh et al., (2017a).
Similar trend was also recorded in harvest index.
Table 3: Effect of phosphorus and sulphur levels on grain yield, straw yield and harvest index.
Number, fresh and dry weight of nodules increased with advancement of growth stages (Table 4). Number, fresh and dry weight of nodules/plant did not varied significantly among phosphorus, sulphur levels and control at 20 DAS. However, at 40 DAS, application of phosphorus and sulphur significantly enhanced the number, fresh and dry weight of nodules/plant than control. Among the phosphorus and sulphur levels, application of 60 kg phosphorus and 30 kg sulphur/ha recorded significantly higher number, fresh and dry weight of nodules than 20 and 10 kg sulphur/ha and phosphorus respectively. Higher number, fresh and dry weight of nodules at higher phosphorus and sulphur dose might be due to higher dose of phosphorus increase in the proliferation of lateral and tap root system. Similar result was recorded by Rathour et al., (2015).
Sulphur application increases nodulation by enhancing the contribution of sulphur hold proteins which are pivotal role for proliferation and growth of rhizobia. Similar finding was recorded by Patel et al., (2018b).
Optimum dose of phosphorus and sulphur for summer greengram
Table 4: Effect of phosphorus and sulphur levels on no. of nodule per plant, fresh and dry weight of nodule per plant.
The response of phosphorus and sulphur on grain yield of summer greengram was worked out to be quadratic. The grain yield of greengram enhanced with enhancing the level of phosphorus and sulphur up to certain levels of phosphorus and sulphur there after it decreased with increasing levels of phosphorus and sulphur. The optimum dose of phosphorus and sulphur for summer greengram was found to be 51.0 (Fig 1) and 24.5 (Fig 2) kg/ha respectively.
Fig 1: Effect of phosphorus on grain yield of summer greengram.
Fig 2: Effect of sulphur on grain yield of summer greengram.