Does a Soybean Intercrop Increase Nodule Number, N Uptake and Grain Yield of the Followed Main Crop Soybean?

Abstract

It is not known whether seed inoculated soybean intercropping can increase the number of nodules, nitrogen uptake and yield of the subsequent main crop, soybean. For this reason, the soybean intercropping approach, sole or mixed cropping with buckwheat, was adopted to examine the influence of inoculation and intercropping of soybean and buckwheat on the subsequent main crop, soybean. Field trials were conducted from 2016 to 2019 in Germany and Poland. For this purpose, soils on which soybeans had not been grown in the past were selected as experimental plots and laid out in a split-plot design. It was surprising that even without inoculation a nodule growth could be documented. However, intercrop inoculation resulted in an average of 12 times more nodules per plant at four out of five sites. In addition, a 43% higher number of nodules was found on the lateral roots of the main soybean crop when intercropping with inoculated soybean occurred. The influence of the intercrop on the main crop soybean also depended on their growth in late summer and autumn. Further, there was a medium relationship (R = 0.7) between the number of nodules in the intercrop soybean and the nitrogen content of the soybean grain in the main crop. In terms of soybean grain yield, a single inoculation of the intermediate soybean crop contributed an average of 5% higher yield and inoculation of both the intercrops, and the main crop improved yield by 15%.

Total chlorophyll and root nodules at various ages of soybean plants (Glycine max L.) in the wet-dry season

“…Not all of the root nodules formed were effective in fixing N. Root nodules that were small in size and spread over the roots of branches were relatively ineffective in fixing N. More nodules will increase N content and leaf chlorophyll. Root nodule' amount and N content have a strong correlation [8]. But too high N content reduces chlorophyll content [3].…”

“…Soybean plants planted on land that has never been planted with soybeans will produce a small number of root nodules compared to soybeans planted on land that is often planted with legumes. The root nodules' amount can be increased by inoculation of N-fixing bacteria [8]. The soil for research every year in the dry season is always planted with soybeans and the results of the study show that the number of nodules is relatively small (fig.…”

Maize and Soya Bean Response to the Residual Influence of Early-Season Cropping System and Fertiliser Applications

“…The favourable response of crops to organic fertiliser in this region has been documented (Imoloame and Ahmed, 2018). Likewise, a study conducted by Porte et al (2022) has reported the favourable response of subsequent crops to the residual effects of the organic fertiliser applied to a previous crop. However, the sole use of organic fertilisers is not viable due to the large quantities required to satisfy crop nutrient demand.…”

“…The application of inorganic fertilisers provides nutrients instantaneously to the crops (Ohyama et al, 2017;Díaz-Chuquizuta et al, 2022). Despite the high cost of inorganic fertilisers, they have minimal effects on the subsequent crops (Porte et al, 2022), while their frequent application leads to soil acidification and soil organic matter reduction, thus threatening soil health (Mumbach et al, 2019). The favourable response of crops to organic fertiliser in this region has been documented (Imoloame and Ahmed, 2018).…”