Effect of Integrated Nutrient Management Practices on Growth and Yield of Groundnut (Arachis hypogaea L.) in an Alfisols of Tamiraparani Tract

Groundnut (Arachis hypogaea L.) crop is native to South America.  It is an excellent source of nutrition to both human and animal due to it’s high nutritive values having 26 %   protein, 12 % starch, 5% minerals and 9 % fibres. India  holds head position in the worldwide oilseed scenario accounting 6.7 million hectares of total area (Anonymous, 2017) and production was 7.4 million tonnes with the productivity of about 1.46 tonnes per ha.
       
Groundnut is cultivated in Tamil Nadu in an area of 2,82,000 ha contributing 5,82,000 tonnes groundnut production, which is 12% of national production. The productivity of groundnut in Tamil Nadu is about 2.08 tonnes per ha compared to national average of 1.46 tonnes per ha (Anonymous, 2017). Hence, nutrient management strategies should be aimed at achieving the goals of productivity and sustainability with minimum cost of organic nutrients.  Poultry manure, humic acid (HA) and Rhizobium spp. contain all the essential plant nutrients and it improves the soil fertility. Regular and imbalanced application of inorganic nutrient sources by omitting organic leads to reduction in soil health besides restricting groundnut productivity (Thulasiram et al., 2018). The lack of well-decomposed organic sources such as manure from poultry, manure from farms, rhizobium and humic acid contributes to low production. Though many studies have been carried out in groundnut crop, the soil test crop response (STCR) on integrated nutrient management for groundnut in an Alfisols of Tamiraparani tract is lacking. Therefore a study was undertaken to evaluate the soil test crop.  response integrated nutrient management package on the growth and yield of groundnut.
 

A field experiment was conducted to study the integrated nutrient management on growth and yield of groundnut (Arachis hypogaea L.) during Rabi season of (September to December) 2019  and 2020 at Agricultural College and Research Institute, Killikulam, Thoothukudi with the test crop of groundnut variety TMV (Gn) 13. The field was located at 80°46' latitude and 77°51' longitude. The elevation of the site was 40 m above sea level. Thoothukudi region coming under alluvial Tamiraparani river basin and semi arid condition received 750 and 785 mm, rainfall during 2019 and 2020, respectively. The daily mean maximum and minimum temperatures for the cropping period were 33.3 and 25.4°C during 2019 and 34.4 and 25.6°C during 2020, respectively. The experimental soil’s texture was sandy clay loam (Scl).  The soil was nearly neutral in reaction (pH 6.79 and 6.82), EC (0.13 and 0.16 dSm^-1), low in organic carbon (0.45 and 0.48%), low available N (212 and 218 kg ha^-1), medium available P (16.4 and 18.5 kg ha^-1) and available K (228 and 215 kg ha^-1). The 10 treatments consisted of combination 2 levels of soil test crop response (STCR) recommended fertilizers (STCR, 38 : 64 : 94 N-P₂O₅-K₂O kg ha^-1) i.e, 75 and 100% and three organic manures, poultry manure @ 3 t ha^-1, Humic acid @ 20 kg ha^-1 and Rhizobium  @ 3 kg ha^-1 along with absolute control that received no manures or fertilizers. Ten treatments viz., T₁ - 100% STCR based NPK @ 38 : 64 : 94 kg ha^-1, T₂ - 75% STCR + Poultry manure @ 3 t ha^-1, T₃ - 75% STCR + Rhizobium  @ 3 kg ha^-1, T₄ - 75% STCR + Humic acid @ 20 kg ha-¹, T₅ - 75% STCR + Humic acid @ 20 + Rhizobium @ 3 kg ha^-1, T₆ - 75% STCR + Rhizobium @ 3 kg ha^-1  + Poultry manure @ 3 t ha^-1, T₇ - 75% STCR + Humic acid @ 20 kg ha^-1  + Poultry manure @ 3 t ha^-1, T₈ - 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry  manure @ 3 t ha^-1, T₉ -  Poultry manure @ 3 t ha^-1,  T₁₀ -  Absolute control.
       
The STCR fertilizers (urea, single super phosphate and muriate of potash) and manures as per treatment was applied at sowing. The experiment was laid out in a randomized block design (RBD) with 3 replications. The observations on plant height, no. of branches plant-1 were recorded manually on five randomly selected representative plants from each plot of each replication separately as well as pod and haulm yield attributing character were recorded as per the standard method. The pod and haulm yield was recorded from net plot area of each treatment. Nutrient (NPK) concentration in plant samples, nutrient uptake and post harvest soil were determined as per standard procedures. The economics were worked out using market prices of output. The data obtained from various characters under study were analyzed by the method of analysis of variance as described by (Gomez and Gomez, 1984). 

Growth attributes
 
Among treatments, 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈) recorded the tallest plant (67.2 cm) and minimum days (31.1 days) required to 50% flowering during both years. This was followed by 75% STCR + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₇) and they were on par with each other. Integration of humic acid and poutry manure with 75% STCR fertilizers markedly enhanced the plant height and days to 50% flowering over 100% STCR fertilizers alone or poultry manure alone. The use of three organic sources as rhizobium, humic acid and poultry manure with 75% STCR fertilizer recorded significantly higher plant height and minimum days required to 50% flowering among all treatments, while unfertilized absolute control has the poor performance of these parameters. The growth attributes were similar trend in both years. The integrated sources of nutrients through fertilizers and organics might have increased plant height and minimum days required for 50% flowering. Similar findings were reported by Khaim et al., (2013) and Sarathi et al., (2014). The association of nutrients from inorganics and organics produced more number of leaves with height of plants. Particularly association of nitrogen nutrients with cell division and photosynthesis might have helped the plants to produce more leaves. This is in accordance with the findings of Choudhary et al., (2017) and Thakur et al., (2018). The increase in plant height and more leaves resulted in significant increase dry matter production (DMP). Rhizobium, humic acid and  poultry manure with 75% STCR fertilizer recorded significantly higher DMP than all other treatments (8854 kg ha^-1, means of 2 years).
 
Yield attributes
 
The different organics with 75% STCR recommended fertilizers had significant influence on the pods plant-1, 100 pods weight and 100 kernels weight (Table 1). Application of 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈) recorded the maximum number of pods plant-1 (67.4), 100 pods weight (71.2 g) and100 kernels weight (36.4 g) and  over rest of the treatments in both years while absolute control resulted in lowest values of pods plant^-1 (26.4), 100 pods weight (27.8 g) and 100 kernels weight (31.4 g). Application of 75% STCR + Rhizobium + Humic acid + Poultry manure might have promoted higher growth rate from the early stage onwards in terms of plant height, pod weight, kernel weight as well as dry matter production. Thus the optimum growth of the plant due to favourable nutritional environment and higher uptake of nutrients might have favoured significant increase in number of pegs plant-1 and thus more number of pods plant^-1. This is in agreement with the findings of Falodun et al., (2015) and Aruna and Sagar (2018). 75% STCR + Rhizobium + Humic acid + Poultry and 75% STCR + Humic acid + Poultry are at on par with each other during both the years of study.
 

 
Yield
 
The nutrient management practices had significant influence on pod and haulm yield of groundnut during both the years (Table 2). The pod and haulm yield were significantly higher (2964 and 8975 kg ha^-1, respectively)  at 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈). This was followed by 75% STCR + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₇) and they were on par with each other. The absolute control recorded the lowest pod and haulm yields (1522 and 4849 kg ha^-1, respectively). Application of 75% STCR + Rhizobium + Humic acid + Poultry manure increased the pod and haulm yields significantly over all other treatments during both the years. However, the haulm yield of 75% STCR + Rhizobium + Humic acid + Poultry manure and 75% STCR + Humic acid + Poultry manure in both years were at on par. Higher pod yield could be attributed to favourable changes in physical and chemical characteristics of the soil which might have enable better pod formation. Moreover, the positive influence of these treatments through immediate supply of nutrients from inorganic sources especially at early stage of the crop and slow and steady supply of nutrients from poultry manures, rhizobium and humic acid throughout the crop growth period might have improved adequate biomass production and improvement in yield parameters resulting in higher pod and haulm yield. Earlier reports also confirmed the significant increase in pod yield of ground nut due to integrated application of nutrients (Zalate and Padmani 2009 and Vala et al., 2018).
 

 
Quality
 
The oil and protein yield was also influenced by the application of STCR recommended NPK with different organic manures (Fig 1 and 2). Application of 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid  20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈)  recorded the highest oil and protein content (50.24 and 25.72, per cent, respectively) and yield (1014  and 536  kg ha^-1) followed by 75% STCR + 20 kg of humic acid ha^-1 + Poultry manure @ 3 t ha^-1 (T₇) which registered the next best oil  and protein content (49.10 and 25.21 per cent) and yield of  962 and 497  kg ha^-1. The absolute control (T₁₀) was recorded the lowest oil and protein yield (348 and 187 kg ha^-1). Application of  75% STCR +3 kg ha^-1of Rhizobium + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈)  provided the significant improvement in the oil and protein yield of groundnut seeds. Eisa., (2011) and Saini et al., (2017) reported that the humic acid influenced the oil and protein in groundnut. So, the humic acid can be contribute to increasing the yield and similarly improving the oil and protein yield.
 

 

 
Nutrient content, uptake and soil nutrient status

Application of inorganic fertilizers in combination with organic manures had significantly influenced the N, P and K content and uptake by groundnut crop during both the years of study (Table 3). The highest N, P and K  content (3.9, 0.5 and 2.79 per cent, respectively) was observed in the treatment with 75% STCR + Rhizobium 3 kg ha^-1 + Humic acid  20 kg ha^-1 + Poultry manure@ 3 t ha^-1 (T₈) . The next highest N, P and K content (3.74,0.45 and 2.54, per cent respectively) was observed in the treatment received with 75% STCR + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1  (T₇). Among the treatments, application of 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈) recorded significantly higher N, P and K uptake (195, 22.9 and 166 kg ha^-1, respectively) than rest of the treatments. This was followed by 75% STCR +  Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₇) (176, 19.9 and 146 kg ha^-1, respectively) and they were at on par. The uptake of major nutrients increased with 75% soil test crop responded recommended fertilizers and organic amendments application. Similar results were reported by Prasad et al., (2005) and Kara et al., (2006). Among the different treatments, the inorganic fertilizers alone or organic alone registered lower uptake of N, P and K. The application of 75% soil test crop response recommended fertilizers with organic sources favoured higher root and shoot development which might have also increased the uptake of N, P and K. The poultry manures, rhizobium and humic acid besides supplying major and minor plant nutrients, might have influenced the physical properties favourably resulting in better soil structure, greater water retention, more favourable environment for root and pod development ultimately registering increased nutrient uptake. This is evidenced from the reports of Chitdeswari et al., (2007) and Ravi et al., (2010).
       

 
Similar trend was as that of uptake of nutrients, the available nutrients status after harvest of crop was observed. The two levels of fertilizers with different levels of organic manures significantly influenced the available nutrients (NPK) after harvest of groundnut crop during both the years of study (Table 4). The soil available N, P and K were maximum (275, 14.8 and 288 kg ha^-1, respectively) in 75% STCR + Rhizobium @ 3 kg ha^-1 + Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₈) and it was significantly superior to rest of the treatments. This was followed by 75% STCR +  Humic acid @ 20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₇) with the higher available N, P and K (253, 12.7 and 273 kg ha^-1, respectively). The lower status of available NPK was recorded in fertilizer alone or organic manure alone applied treatments. The absolute control registered lowest status of available N, P and K (180, 8.6 and 180 ka ha^-1, respectively). The rate of release of nutrients from organic manures may depend on initial chemical composition together with the stage of composting. The highest available N, P and K in soil due to combination of fertilizers with  organic sources which increased the post harvest soil by mineralization. Similar finding were reported by Karunakaran et al., (2010) and Ramakrishna et al., (2017).
 

 
Economics
 
The economics (Table 2) data reveal that the application of  STCR of fertilizer as 38:64:94  kg of NPK ha^-1 with humic acid @    20 kg ha^-1 + rhizobium 3 kg  ha^-1 and poultry manure @ 3 t ha^-1 (T₈) was the best treatment with net income of   72,706 ha^-1  with benefit cost ratio of 2.47 followed by treatment of 75% STCR + Humic acid  20 kg ha^-1 + Poultry manure @ 3 t ha^-1 (T₇)  with next best net income of ( 66,375) with the B:C ratio of 2.35. The poor net income and benefit: cost ratio was obtained from absolute control (T₁₀) ( 23,715 and 1.53). Due to the poultry manure is a very cheap source compared to all other inputs and it has an high nutrient content. So, it could be increasing the highest net income. The earlier findings of were also supported for this result Akbari et al., (2011) and Gurni and Nath (2012).

It is concluded that in areas where organics are available at cheaper prices, the application of STCR recommended fertilizer as 75% STCR + 3 kg of Rhizobium ha^-1 + 20 kg of Humic acid ha^{- 1}+ Poultry  manure @ 3 t ha^-1 (T₈)  is effective to maximize the yield and income of groundnut farmers of Alfisols of  the Tamiraparani tract.

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