Effect of Gypsum, Nitrogen and Phosphorus on Growth, Yield and Quality of Spring Groundnut

Groundnut (Arachis hypogaea L.) is known as the king of oilseeds and belongs to the family Leguminosae and sub-family Papilionoideae. Imbalanced and inadequate use of nutrients is the main reason for lower yield of groundnut. Since groundnut is a legume-oilseed crop, its requirement of phosphorus, calcium and sulphur is quite high. Gypsum is commonly used as a source of calcium and sulphur for groundnut all over the world. Deficiency of calcium leads to the production of immature pods, black embryo in seed, weak germination of seeds and increases production of aflatoxin and thus, decays peanut pod (Agasimani et al., 1992; Evanylo, 1989; Grichar, 2002; Murata, 2003). Calcium uptake is highest during the early stages of fruit development mainly pod expansion and seed growth (Boote 1982). It was observed that withholding Ca from the pegging zone (0-8 cm soil depth) during the first 30 days after initial pegging severely reduces seed size and dry weight as compared to withholding Ca at the other stages of growth (Smal et al., 1989). Sulphur is a component of protein and has an important role to play in oil synthesis. It also increases chlorophyll synthesis and decreases chlorosis. Phosphorus plays a significant role in nodule formation and fixation of atmospheric nitrogen (Brady and Well, 2002). Phosphorus application determines plant reproductive efficiency and promotes growth, development and yield of groundnut crop (Savani and Darji, 1995; Bairagi et al., 2017). The nitrogen requirement of nodulated groundnut cannot be met from symbiotic nitrogen fixation alone. However, to meet the nitrogen requirement during early growth stages, nitrogen could be applied as starter dose (Iman and Ahmed, 2014). However, very less information on the balanced nutrition of spring groundnut is available. Therefore, there is a need to develop a nutrient management strategy to achieve the potential production of spring groundnut. Keeping all these points in view the present study was undertaken to find out the optimum mineral nutrition of spring groundnut.

The field trials of the present investigation were conducted at the Students’ Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana during spring season of 2018 and 2019. Soil of experimental field was normal alkaline in pH (8.17) and electrical conductivity (0.58 dS m^-1), low in organic carbon (0.33%), available nitrogen (156.1 kg ha^-1) and available calcium (114 ppm) while medium in available phosphorus (16.29 kg ha^-1), available potassium (323.5 kg ha^-1) and available sulphur (24.8 kg ha^-1). The experiment was laid out in a split plot design replicated three times with four gypsum levels (0, 125, 175 and 225 kg ha^-1) in combination with two stages of gypsum application (Full at sowing and 50% at sowing + 50% at flower initiation stage) in the main plot and three levels of nitrogen and phosphorus (15 kg N ha^-1 + 20 kg P₂O₅ ha^-1, 25  kg P₂O₅ ha^-1 and 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1) in the sub-plot. Second split of gypsum was applied at flower initiation stage i.e. at 30 days after sowing while all the doses of nitrogen and phosphorus were applied at the time of sowing. Groundnut variety ‘TAG 37A’ was sown at the spacing of 30 cm × 15 cm on second week of March during both the years. All the recommended packages of practices were adopted. Nitrogen and phosphorus were applied through DAP while the remaining nitrogen requirement was met by using urea. The number of plants per metre row length were counted at 10, 12 and 14 days after sowing (DAS) from two spots in the inner rows of the plot and this was represented as emergence count. Five plants were tagged randomly in each plot and were used to measure the plant height and number of branches plant^-1 at 30, 60 and 90 DAS and at harvest. One plant was cut at ground level randomly from each plot at 30, 60 and 90 DAS and at harvest to determine dry matter accumulation. After harvesting of the crop, five tagged plants from each plot were selected to count the number of pods plant^-1, 100-kernel weight, shelling percentage, sound mature kernels percentage. Pod yield, haulm yield and kernel yield were determined on net plot basis and converted into per hectare yield. The economics was calculated based on the standard prevailing market prices of various inputs. Nitrogen content in kernel was determined by Kjeldahl’s method and protein content was calculated by multiplying N content with the factor 6.25. Oil content was determined by using standardised Nuclear Magnetic Resonance (NMR) instrument and oil percentage was recorded on weight basis.

Growth attributes
 
Different levels of gypsum exerted positive influence on the emergence count, plant height, number of branches and dry matter accumulation of spring groundnut (Fig 1 and 2). The maximum emergence count was observed with highest level of gypsum (225 kg ha^-1) and lowest with control. The increase in dose of gypsum from 0 to 225 kg ha^-1 also increased the plant height, number of branches and dry matter accumulation at all the stages of crop growth  Maximum plant height, number of branches and dry matter accumulation at 30, 60, 90 DAS and at harvest were obtained with the application of 225 kg ha^-1 gypsum. Singh (2007), Yadav et al., (2015) and Yadav et al., (2017) also supported the findings of the current study and reported that the progressive increase in the level of gypsum upto 324 kg ha^-1 resulted in significantly increased growth parameters over control. Gypsum application stage also influenced emergence count of groundnut and maximum was observed withfull dose of gypsum application at sowing (Fig 1). Split application of gypsum (50% at sowing + 50% at flower initiation stage) resulted in higher plant height, number of branches and dry matter accumulation of groundnut as compared to the application of full dose of gypsum at sowing at all the stages except at 30 DAS. It was due to the reason that the second split of gypsum was applied at flower initiation stage i.e. at 30 DAS, therefore its effect could not show up in the data of growth parameters recorded at 30 DAS. The results are in accordance with the findings of Ghosh et al., (2015) who observed that the growth parameters were significantly increased with the split application of gypsum (50% basal + 50% top dressing) as compared to the basal application of gypsum. The maximum emergence count was observed with 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1and lowest with 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1 (Fig 1). Plant height, number of branches and dry matter accumulation were positively affected by different levels of nitrogen and phosphorus (Fig 1 and 2). Maximum plant height of 5.40 cm (30 DAS), 25.75 cm (60 DAS), 43.56 cm (90 DAS) and 52.95 cm (at harvest) was observed with the application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 and it was followed by 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1 and 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1 (Fig 1). At 30 DAS, 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 resulted in significantly higher number of branches as compared to the other levels. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 resulted in maximum number of branches (5.43 at 30 DAS, 9.09 at 60 DAS, 10.57 at 90 DAS and 11.93 at harvest) which was followed by 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1 and 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 resulted in maximum dry matter accumulation per plant (5.63 g at 30 DAS, 16.94 g at 60 DAS, 30.81 g at 90 DAS and 39.5 g at harvest) which was followed by 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1 and 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1. Kabir et al., (2013) and Hasan and Sahid (2016) also supported same findings and reported that the application of phosphorus and nitrogen @ 82 kg P₂O₅ ha^-1 and 27 kg N ha^-1 increased the plant height, number of branches and dry matter accumulation as compared to the lower levels of nitrogen and phosphorus.
 

 

 
Yield attributes
 
Total number of pods, 100-kernel weight, shelling percentage and sound mature kernels were observed to have been significantly influenced by the use of different levels of gypsum (Table 1). Application of 225 kg ha^-1 gypsum resulted in significantly higher total number of pods as compared to the other lower doses of gypsum. Application of 225 kg ha^-1 gypsum resulted in maximum 100-kernel weight (46.23 g) and sound mature kernels percentage (83.04%) which were statistically at par with 175 kg ha^-1 and 125 kg ha^-1 gypsum, while significantly higher than that of control. Application of 225 kg ha^-1 gypsum resulted in maximum shelling percentage (68.38%) which was statistically at par with 175 kg ha^-1 gypsum, while significantly higher than that of 125 kg ha^-1 gypsum and control. Mandal et al., (2005), Sivanesarajah et al., (1995), Thilakarathna et al., (2014) and Yadav et al., (2015) supported these results by concluding that the application of gypsum up to 500 kg ha^-1 resulted in maximum yield attributes of groundnut than the lower gypsum doses. Gypsum application stage also had a significant influence on the total number of pods, shelling percentage and sound mature kernels. Split application of gypsum (50% at sowing + 50% at flower initiation stage) gave significantly more total number of pods (46.34), shelling percentage (67.78%) and sound mature kernels percentage (82.74%) as compared to the application of full dose of gypsum at sowing. The maximum test weight (45.91 g) was observed with the split application of gypsum though the differences were non-significant. The results are supported by Jat and Singh (2006) and Ghosh et al., (2015) who reported that the number of pods plant^-1 were significantly increased with the split application of gypsum as compared to application of full dose of gypsum at the time of sowing. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 resulted in maximum number of pods (47.08), shelling percentage (67.9%) and sound mature kernels percentage (83%), which were statistically at par with the application of 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1 while significantly more than the application of 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1. The effect of nitrogen and phosphorus levels on the 100-kernel weight of groundnut was non-significant. However, an increasing trend was observed in the 100-kernel weight (45.1 g to 45.93 g) with an increase in the levels of nitrogen and phosphorus though the difference was non-significant. Similarly, Meena and Yadav (2015) found that the application of 30 kg N ha^-1 + 60 kg P₂O₅ ha^-1 significantly increased the yield attributes over lower doses.


 
Yield
 
Different gypsum levels exerted a significant influence on the pod yield, haulm yield and kernel yield of groundnut (Table 1). With an increase in the levels of applied gypsum, an increasing trend in the pod yield, haulm yield and kernel yield was observed. Application of 225 kg ha^-1 gypsum resulted in maximum pod yield (44.94 q ha^-1) and haulm yield (126.46 q ha^-1), which was significantly higher as compared to the other doses (Control, 125 and 175 kg ha^-1) of gypsum. Application of 225 kg ha^-1 gypsum resulted in maximum kernel yield (30.76 q ha^-1), which was at par with 175 kg ha^-1gypsum while significantly higher as compared tocontrol and 125 kg ha^-1 of gypsum. Gashti et al., (2012), Yadav et al., (2015) and Pancholi et al., (2017) confirmed the above results and reported that 200 kg ha^-1 gypsum application upto 400 kg ha^-1 resulted in maximum pod yield and straw yield of groundnut. Gypsum application stage significantly influenced the pod yield, haulm yield and kernel yield of spring groundnut. The split application of gypsum (50% at sowing + 50% at flower initiation stage) gave significantly higher pod yield (41.24 q ha^-1), haulm yield (117.82 q ha^-1) and kernel yield (28 q ha^-1) as compared to the application of full dose of gypsum at sowing. Harvest index was non-significantly affected by gypsum application stage. However, split application of gypsum gave higher harvest index (25.97) as compared to the basal application of gypsum (25.73). The findings are in line with the results of Jat and Singh (2006) who reported that the split application of gypsum @ 250 kg ha^-1 at sowing + 125 kg ha^-1 at flowering significantly increased the pod yield and kernel yield over gypsum application at sowing time. Nitrogen and phosphorus levels had a significant effect on the pod yield, haulm yield and kernel yield of spring groundnut. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 gave maximum pod yield (41.67 q ha^-1), haulm yield (118.39 q ha^-1) and kernel yield (28.34 q ha^-1), which were statistically at par with 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1 (38.68 q ha^-1 in 2018 and 42.36 q ha^-1 in 2019) while significantly higher than that of 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1. Nitrogen and phosphorus levels had a non-significant effect on harvest index, however an increasing trend in harvest index was observed with increase in the levels of nitrogen and phosphorus. Similarly, Meena and Yadav (2015) found that the application of 30 kg N ha^-1 + 60 kg P₂O₅ ha^-1 significantly increased the pod yield, haulm yield and kernel yield of groundnut over lower doses of nitrogen and phosphorus.
 
Quality attributes
 
Different gypsum levels exerted a significant influence on the protein and oil content of kernels (Table 1). Application of 225 kg ha^-1 gypsum resulted in maximum protein content (27.12%) which was statistically at par with that of 175 kg ha^-1 and 125 kg ha^-1 gypsum while significantly higher than control. Application of 225 kg ha^-1 gypsum gave maximum oil content of 47.93%, which was significantly higher as compared to the other doses of gypsum. Rao and Shaktawat (2001), Rao and Shaktawat (2005) and Thilakarathna et al., (2014) also reported that application of 250 kg gypsum ha^-1 significantly improved the protein content and oil content as compared to control. The effect of gypsum application stage on the protein content and oil content of groundnut kernels was non-significant. The maximum protein content and oil content was observed with the split application of gypsum as compared to full gypsum application at sowing time though the difference was non-significant. Different levels of nitrogen and phosphorus exerted a significant effect on the protein and oil content of groundnut kernels. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 gave maximum protein content (27.41%) and oil content (47.71%), which was significantly higher than the other two levels of nitrogen and phosphorus. Similarly, (Shinde et al., 2000) and Hasan and Sahid (2016) revealed that the increase in levels of nitrogen and phosphorus increased the protein and oil content in the kernels of groundnut.  
 
Economics
 
Gypsum levels influenced gross returns, net returns and benefit cost ratio significantly (Table 2). Application of 225 kg ha^-1 gypsum resulted in maximum gross returns (₹ 172786.9 ha^-1), net returns (₹ 119313.2 ha^-1) and benefit cost ratio (3.23), which were significantly higher than other levels of gypsum. Gypsum application stage significantly influenced the gross returns, net returns and benefit cost ratio. Split application of gypsum (50% at sowing + 50% at flower initiation stage) gave significantly higher gross returns (₹ 158645.6 ha^-1), net returns (₹ 105992.2 ha^-1) and benefit cost ratio (3.00) as compared to the application of full dose of gypsum at sowing during both the years. Nitrogen and phosphorus levels influenced gross returns and net returns significantly. Application of 35 kg N ha^-1 + 40 kg P₂O₅ ha^-1 gave maximum gross returns (₹ 160303 ha^-1) and net returns (₹ 106042.8 ha^-1), which were at par with 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1, but significantly higher than 15 kg N ha^-1 + 20 kg P₂O₅ ha^-1. Nitrogen and phosphorus levels influenced the benefit cost ratio non-significantly. However, an increasing trend in the value of benefit cost ratio was observed with increase in the levels of nitrogen and phosphorus.
 

The application of higher level of gypsum @ 225 kg ha^-1 resulted in significantly maximum yield and also improved growth and quality parameters of spring groundnut over lower levels. In spring groundnut, gypsum should be applied in two split doses i.e. half at sowing time and remaining half at flower initiation stage to get more growth, yield and quality of groundnut. To get maximum growth, yield and quality of spring groundnut, the crop should be applied with 25 kg N ha^-1 + 30 kg P₂O₅ ha^-1.

None.