Influence of yellow gypsum on nutrient uptake and yield of groundnut in different acid soils of Southern India

Seasonal conditions during crop growth

The groundnut crop produces optimum yield in the regions receiving rainfall between 200 to 1000 mm⁸. The total rainfall during groundnut growing season was 257.10 mm and 403.10 mm at Baljigapade in 2018 and 2019, respectively, wherein Pavagada (2018) total rainfall was 53.90 mm (Fig. 1). In 2018, both Pavagada and Baljigapade received very low and negligible rainfall during the reproduction and harvest stage of groundnut. Optimum temperature for groundnut production ranges between 20 to 30 °C and growth and pod formation limited below 16 °C and above 32 °C⁹. The monthly mean atmospheric temperature was ranged from 23 to 27 °C and 21 to 26 °C at Baljigapade in 2018 and 2019, respectively, wherein Pavagada ranged from 25 to 28 °C. At all three locations, the monthly mean atmospheric temperature was slightly high during the early vegetative growth of groundnut and it was progressively decreased as the crop reaches its maturity stage (Fig. 1). All three locations recorded higher and lower mean monthly sunshine hours (hours day⁻¹) during peg initiation to pod filling stage (September and October) and early vegetative growth of groundnut (July and August), respectively.

Growth parameters of groundnut

Analysis of variance revealed that treatment, location, and their interaction had a significant effect on plant height and number of branches at harvest (P < 0.01) (Fig. 2a,b). Application of gypsum at different rates resulted in a significant difference in the plant height and number of branches at all three locations except on plant height at Baljigapade during 2018. Irrespective of the locations, higher and lower plant height and number of branches was observed with treatment receiving 625 kg YG ha⁻¹ as basal + split and 500 kg NG ha⁻¹ as basal, respectively. With respect to different times of YG application, plant height was not significantly influenced, except at Baljigapade in 2019. However, basal + split application treatments recorded a significantly higher number of branches over basal application treatments.

Yield and yield components of groundnut

Yield components of groundnut were significantly affected by different treatments and locations. Further, there was no significant difference observed due to its interaction (Table 3). Application of YG at different rates significantly affected the yield components of groundnut at all three locations, except 100 kernel weight and shelling percentage at Pavagada and Baljigapade in 2018, respectively. Significantly higher yield components were recorded with basal and basal + split application of 625 kg YG ha⁻¹ and lower yield components were recorded with control. Regardless of the locations, application of YG at different times had no significant effect on the number of pods plant⁻¹. However, significant differences in 100-kernel weight and shelling percentage were observed at Baljigapade in 2019.

Analysis of variance showed that different treatments significantly affected the pod and haulm yield, while different locations significantly affected the haulm yield and harvest index (Table 3). The treatment and location interaction had no significant effect on pod and haulm yield and harvest index of groundnut. YG receiving treatments recorded increase in pod yield over control, which ranged 1.08–10.76% at Pavagada (2018), wherein Baljigapade it ranged 10.76–1.80% and 12.71–0.44% in 2018 and 2019, respectively. Application of YG at different time had no significant effect on pod yield at Baljigapade, however, at Pavagada basal + split application of 625 kg YG ha⁻¹ (2753.91 kg ha⁻¹) recorded significantly higher pod yield than the basal application of 625 kg YG ha⁻¹ (2653.97 kg ha⁻¹).

The pod yield of groundnut was significantly and positively correlated with total uptake of Fe (r = 0.95*), Mn (r = 0.99**), Zn (r = 0.96*), Cu (r = 0.93*), and Si (r = 0.96*) by crop (see Supplementary Fig. S1 online). The haulm yield was significantly different among treatments at all three locations and recorded higher with YG receiving treatments than in NG receiving treatments. Haulm yield at Pavagada (2018) and Baljigapade (2018 and 2019) was increased by 11.84%, 6.97%, and 15.71%, respectively, in the basal + split application of 625 kg YG ha⁻¹ compared with NG. Haulm yield of groundnut was significantly and positively correlated with total uptake of Fe (r = 0.92*), Mn (r = 0.88*), Cu (r = 0.97**) and Si (r = 0.96**) (see Supplementary Fig. S1 online). Irrespective of the locations, the harvest index of groundnut was not significantly affected by application of YG at different rates and time.

Changes in physiochemical properties of post-harvest soil

Post-harvest soil pH differed significantly among different treatments and locations, while post-harvest soil electrical conductivity (EC) varied significantly among different locations (Fig. 3a,b). Application of various levels of YG at different times over control had no significant effect on post-harvest soil pH at Baljigapade in 2018. Nevertheless, there was a significant increase in the other two locations. In both Pavagada (2018) and Baljigapade (2019), all the YG receiving treatments observed higher post-harvest soil pH than NG receiving treatment. The application of 625 kg YG ha⁻¹ as basal + split increased the pH of Pavagada soil from 6.93 to 7.76 and from 5.77 to 5.84 and 4.76 to 4.92 in Baljigapade soils in 2018 and 2019, respectively. There was no significant difference among treatments with different time of YG application. Among the locations, Pavagada showed a remarkable change in pH at harvest while the other two locations showed a meager level of change in pH with YG application. Significant changes in EC with YG application were observed at Baljigapade during 2018, but it was not observed at other locations. EC of Pavagada soil ranged from 8.15 to 9.20 mS m⁻¹ and that of Baljigapade soils ranged from 3.91 to 4.02 mS m⁻¹ and 9.83 to 10.66 mS m⁻¹ in 2018 and 2019, respectively. Further, there was no significant difference in EC among different times of YG application and different sources of gypsum.

Effect of YG application on soil micronutrient and silicon status

Treatments, locations, and their interaction had significant effects on the DTPA extractable Fe, Mn, Zn, and Cu contents in post-harvest soils of all the locations (P < 0.01) (Table 4). The DTPA extractable Fe, Mn, Zn, and Cu contents in post-harvest soils were significantly varied with different rates of YG application, except DTPA extractable Cu at Pavagada in 2018. DTPA extractable Fe content in soils varied from 5.34 to 24.63 mg kg⁻¹, with the highest in basal + split application of 625 kg YG ha⁻¹ and lowest in control. Overall, DTPA extractable Fe content in soils increased with increasing YG rates, and all the YG receiving treatments recorded significantly higher DTPA extractable Fe content than NG treatment. DTPA extractable Mn content was higher with basal alone and basal + split application of 625 kg YG ha⁻¹ than in the other treatments. Significantly higher DTPA extractable Zn was noted in the basal + split application of 625 kg YG ha⁻¹ and all the YG receiving treatments recorded significantly higher DTPA extractable Zn than control, expect at Baljigapade in 2018. Significant increase in DTPA extractable Cu was observed with increasing rate of YG, with the higher content in 625 kg YG ha⁻¹ as basal and basal + split application. Basal + split application of YG recorded higher DTPA extractable Fe, Mn, Zn and Cu contents than basal application of YG, but the difference was not significant, except for DTPA extractable Fe and Zn at Baljigapade and Pavagada in 2018, respectively. Overall, higher DTPA extractable Fe (24.63 mg ha⁻¹), Mn (2.74 mg ha⁻¹) and Cu (1.61 mg ha⁻¹) in post-harvest soil was recorded with basal + split application of 625 kg YG ha⁻¹, while higher DTPA extractable Zn (1.98 mg ha⁻¹) was recorded with basal application of 625 kg YG ha⁻¹.

Different treatments, locations and their interaction had significant effect on the acetic acid (AA-Si) and calcium chloride (CC-Si) extractable Si content in post-harvest soil (P < 0.01) (Table 4). Both, AA-Si and CC-Si were found to be significantly increased with increasing rate of YG, however, AA-Si at Baljigapade in 2019 was found to be non-significant. Application of 625 kg YG ha⁻¹ as basal + split recorded significantly higher CC-Si in all locations, where lowest CC-Si was recorded in control. In all the locations, basal + split applications of YG recorded significantly higher CC-Si than basal application of YG. At both the locations in 2018, significantly higher AA-Si was observed with basal + split application of 625 kg YG ha⁻¹. Unlike CC-Si, AA-Si was found to be non-significant among basal and basal + split application of YG treatments. In different treatments, CC-Si ranged from 23.72 to 52.39 mg kg⁻¹, while AA-Si ranged from 19.04 to 56.58 mg kg⁻¹. The pH of post-harvest soil was significantly and positively correlated with availability of AA-Si (r = 0.98**) and CC-Si (r = 0.96**) (see Supplementary Fig. S1 online). In general, YG applied treatments recorded significantly higher AA-Si and CC-Si than NG and Pavagada recorded higher CC-Si and AA-Si than Baljigapade in 2018 and in 2019.

Micronutrients and silicon uptake by groundnut in relation to their availability in soil

Based on the uptake of micronutrients and silicon by groundnut as well as their available content in the soil, the value of plant available nutrient (PAN) recovery coefficient was calculated and presented in Fig. 4. Analysis of variance showed that different treatments, locations and their interactions had significant effect on PAN recovery coefficient of micronutrients. PAN recovery coefficient of micronutrients was found to be significantly varied among different treatments at Pavagada. Significantly higher PAN recovery coefficient of Fe (0.19), Zn (0.11) and Cu (0.11) was recorded with basal + split application of 625 kg YG ha⁻¹, while for Mn (0.38) it was recorded with basal + split application of 500 kg YG ha⁻¹. In Baljigapade, basal + split application of 625 kg YG ha⁻¹ resulted significantly higher PAN recovery coefficient of Zn (0.05) and Cu (0.05), and Fe (0.08) in 2018 and 2019, respectively. Regardless of the location, higher PAN recovery coefficient values of micronutrients were observed with high rate of YG application, while lower PAN recovery coefficient values were observed with NG application. Very low PAN recovery coefficient values of micronutrients (PAN recovery coefficient < 1.0) indicated that soils of all three locations were sufficient for covering nutritional needs of groundnut crop.

For silicon, different treatments and its interaction with location had no significant effect on PAN recovery coefficient of silicon, but found to be significant due to location (P < 0.01) (Fig. 5). PAN recovery coefficient of Si was not varied significantly among different YG receiving treatments, except at Baljigapade in 2018. All the YG receiving treatments recorded lower PAN recovery coefficient value than NG receiving treatment. Higher values of PAN recovery coefficient for silicon (PAN recovery coefficient > 1.0) showed that quantity of this beneficial element in soil was too low to cover plant nutritional requirements.

Micronutrient and silicon uptake by haulm and kernel

Uptake of micronutrients by haulm and kernel of groundnut was found to be significantly affected by different treatments and locations (P < 0.01). Nonetheless, treatment and location interaction had no significant effect on micronutrients uptake by kernel of groundnut (Table 5). Uptake of micronutrients by both haulm and kernel of groundnut largely increased in YG applied treatments, comparing with control treatment. Among different treatments, uptake of Fe, Mn, Zn and Cu by haulm of groundnut was in the range 1562.38–3915.44 g ha⁻¹, 237.08–691.86 g ha⁻¹, 82.69–252.32 g ha⁻¹ and 70.74–193.11 g ha⁻¹, respectively. Irrespective of the locations, treatment received 625 kg YG ha⁻¹ as basal + split recorded significantly higher micronutrient uptake, while lower micronutrient uptake was recorded with 500 kg NG ha⁻¹. Total uptake of Fe, Mn and Cu by groundnut were significantly and positively correlated with availability of Fe (r = 0.93*), Mn (r = 0.91*) and Cu (r = 0.89*), respectively (see Supplementary Fig. S1 online). In general, application of 500 and 625 kg YG ha⁻¹ at different time had no significant effect on micronutrient uptake. Among the locations, significantly higher uptake of micronutrients was observed at Baljigapade in 2019 followed by Baljigapade and Pavagada in 2018.

Different treatments and locations significantly affected the Si uptake by haulm of groundnut (P < 0.01). Nevertheless, treatment and location interaction had no effect on Si uptake by haulm and kernel of groundnut (Table 5). YG application at different rate and time had significant effect on Si uptake by haulm of groundnut and higher Si uptake was observed with basal + split application of 625 kg YG ha⁻¹. Further, all YG receiving treatments had significantly higher Si uptake than NG receiving treatment except treatment receiving 500 kg YG ha⁻¹ as basal. Application of same level of YG as basal alone and basal + split was found to be at par with each other. The Si uptake by kernel was not significantly varied among treatments at Pavagada and Baljigapade in 2018, however, there was significant variation at Baljigapade in 2019. Higher and lower Si uptake by groundnut kernel was observed with basal + split application of 625 kg YG ha⁻¹ (7.39 g ha⁻¹) and basal application of 500 kg NG ha⁻¹ (4.04 g ha⁻¹), respectively.

Economic analysis

Compared to control where 500 kg NG ha⁻¹ was applied, all the YG treatments achieved maximum returns in producing maximum gross income and benefit: cost ratio (Table 6). Maximum gross return (2420.56 US$ ha⁻¹) and benefit: cost ratio (3.00) was achieved by basal + split application of 625 kg YG ha⁻¹. The lowest gross income (2169.72 US$ ha⁻¹) and benefit: cost ratio (2.73) was recorded in treatment where 500 kg NG ha⁻¹ was applied as basal.

Source: Ecology - nature.com