Effect of biofertilizers on phosphorus nutrition and grain yield of des chickpea (Cicer arietinum L.) grown in different agro-ecologies
South African soils are predominantly acidic and have high levels of Al and Fe, giving a higher P sorption capacity and low P levels. Consequently, soil fertility has become a major constraint in South Africa’s farming, thereby threatening crop production and food security. Literature reveals, however, that biofertilizers have the potential to improve crop growth, grain yields and, acid and alkaline phosphatase activities in both the plant tissue and soil. Nonetheless, there is scant information about the biofertilizers’ effects on their co-application with rhizobium inoculation as most of the studies focused on the sole application of the biofertilizers such as Bontera, Kelpak, Mycorrhiza, and Rhizobium inoculation. This study evaluated the biofertilizers’ effects on the phosphorus accumulation in the rhizosphere soil, the acid and alkaline phosphatase activity in the rhizosphere soil and, the two chickpea genotypes’ growth and yields under different environments. In 2019, three field experiments were conducted in three locations, namely Thohoyandou, Syferkuil, and Sikhwahlane, and two more were done at Thohoyandou and Syferkuil in 2021. The treatments consisted of a factorial combination of six biofertilizer levels (Mycoroot, Kelpak, Rhizobium inoculation, Kelpak+Rhizobium inoculation, Mycoroot+Rhizobium inoculation, zero control) and two chickpea genotypes (Accession 3 and Accession 7). These were arranged in a three-time replicated randomised complete block design. The intercepted radiation’s (IR) proportion was measured using the AccuPAR LP-80 ceptometer at Thohoyandou in 2019 and 2021. The chlorophyll content was measured at vegetative and reproductive stage using a chlorophyll meter (CCM-200 PLUS, Opti-Science) at Thohoyandou and Syferkuil in 2021. The stomatal conductance (gs) was measured using a portable porometer (AP4 DELTA-T Device) at the vegetative and reproductive stage at Thohoyandou in 2021. The normalised different vegetation index (NDVI) was measured using the portable GreenSeeker at the vegetative stage at Thohoyandou and Syferkuil in 2021. The chlorophyll fluorescence was measured at the flowering stage using the portable chlorophyll fluorometer at Thohoyandou, Syferkuil, and Sikhwahlane in 2019; and at Thohoyandou and Syferkuil in 2021. The acid and alkaline phosphatase activities were measured at the flowering stage at Thohoyandou, Syferkuil, and Sikhwahlane in 2019, and at Thohoyandou and Syferkuil in 2021. The inorganic phosphorus was measured at the flowering stage at Thohoyandou and Syferkuil in 2021. The yield and yield components (pod weight, shoot biomass, and harvest index) were measured at the harvest maturity stage at Thohoyandou, Syferkuil, and Sikhwahlane in 2019, and at Thohoyandou and Syferkuil in 2021. Data were analysed for variance (ANOVA) using the STATISTIX (2017) version 10.0. The Tukey’s honestly difference (HSD) test was used to separate the means that were significantly different (P≤0.05). The Pearson correlation was used to test the linear association’s strength between the parameters studied. The biofertilizers significantly increased the intercepted radiation’s proportion (%IR) at Thohoyandou in 2019 and 2021. The Kelpak sole and in combination with the rhizobium inoculation on 61DAE (86.71) and 75DAE (85.10) recorded the highest %IR in 2019 cropping season. The rhizobium inoculation recorded the highest %IR at 47DAE (50.17) & 83DAE (80.67) and the Kelpak+Rhizobium inoculation recorded the highest %IR at 61DAE (54.33) & 75DAE (68.67) in the 2021 cropping season. The genotype had no significant effect on %IR in both seasons but the interaction between M x accession7 gave the greatest proportion of the intercepted radiation in 2019. The chlorophyll content was significantly increased by the biofertilizers at Thohoyandou (clay soil) only in 2021 with the Kelpak combined with rhizobium inoculation recording the greatest chlorophyll content (2.13-3.10) in all measurement dates. However, the genotype affected the chlorophyll content at 74DAE with accession7 recording the highest chlorophyll content compared to accession3. However, the interaction between the biofertilizer and the genotype had no significant effects on the chlorophyll content in all sites. The stomatal conductance was significantly affected by the biofertilizer application with K+R recording the highest gs at 42DAE (529.25) and M+R recording the highest gs at 56DAE (473.08) at Thohoyandou in 2021. Both the genotype and interaction between the biofertilizer and the genotype significantly affected the gs at 70DAE with accession3 recording the highest gs compared to accession7, and the Mycoroot x accession3 recording the highest gs. The normalised difference vegetative index was significantly increased by the biofertilizer application at 28DAE & 42DAE at Syferkuil only (sandy soil) with Mycoroot and K+R recording the highest NDVI at 28DAE (0.56) and rhizobium inoculation and M+R recording the highest NDVI at 42DAE (0.68). Neither the genotype nor the interaction between the biofertilizer and the genotype had a significant effect on the NDVI in all sites. The biofertilizer’s application significantly affected the acid and alkaline phosphatase activities in all sites except at Syferkuil in 2021 where the biofertilizers had no significant effect on the alkaline phosphatase activity. The co-application of K+R gave the highest APase at Syferkuil (sandy soil) and Sikhwahlane (loamy soil) in 2019, while at Thohoyandou (clay soil) the co-application of M+R gave the highest APase. In 2021, the co-application of K+R gave the highest APase at Syferkuil and Thohoyandou. The alkaline phosphatase activity was higher with the application of rhizobium inoculation at Syferkuil and Thohoyandou in 2019, and higher with the co-application of M+R (13.03) in Sikhwahlane in 2019. However, the zero control gave the highest AlkPase activity (74.14) at Syferkuil in 2021. At Thohoyandou (2021), however, the Kelpak’s application recorded the highest AlkPase activity (56.81). Inorganic phosphorus was significantly affected by the biofertilizers in both sites. The co-application of K+R recorded the highest inorganic phosphorus at Syferkuil and the sole Kelpak (15.16mg/kg) gave the highest inorganic phosphorus at Thohoyandou in 2021. The genotype had no significant effect on the APase and AlkPase activities but significantly affected the inorganic phosphorus at Syferkuil with accession3 (55.61mg/kg) recording the highest Pi compared to accession7. The interaction between the biofertilizer and the genotype affected the APase and inorganic at Thohoyandou, and only the Pi at Syferkuil in 2021. Among the various biofertilizers used at Thohoyandou, the rhizobium inoculation recorded the highest quantum yield of PSII (0.24 to 0.33) in 2019. The biofertilizers, however, significantly affected the PSII, Fv/Fo, and Fv/Fm at Syferkuil in 2021 with the rhizobium inoculation exhibiting the highest PSII, Kelpak exhibiting the greatest Fv/Fo, and the sole Mycoroot and Mycoroot combined with the rhizobium inoculation exhibiting the strongest Fv/Fm. Among the biofertilizers administered at Thohoyandou, the Kelpak and rhizobium inoculations gave the highest PSII, and the Kelpak sole gave the greatest Fv/Fo. The genotype significantly affected the minimal fluorescence (Fo) in Sikhwahlane in 2019. It was pronounced in accession7 than in accession3 and the genotype affected the Fv/Fm at Syferkuil and was more pronounced in accession7 than in accession3. In 2019’s cropping season, the biofertilizers increased the pod weight and grain yields at Thohoyandou to above-ground biomass and grain yield at Syferkuil, and pod weight to above-ground biomass and the grain yield in Sikhwahlane. In both sites in 2021, the biofertilizers increased the above-ground biomass, harvest index, and grain yield. Accession7 gave the highest value of pod weight at Syferkuil’s cropping season in 2021. The interaction between the biofertilizer and the genotype had no significant effect on the grain yield and yield components in all the locations and in both cropping seasons. Therefore, this makes the biofertilizers an effective tool for increasing the chickpea’s yield in these regions.
Biofertilizers, Chickpea, Kelpak, Mycoroot, Rhizobium inoculum, P-enzymes, UCTD
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