## 4 Discussion
### Crop Productivity  
Studies evaluating the relationship between phosphorus doses (52.32 and 4.36 mg dm\({}^{-3}\) of P) in potted plants, without maintenance fertilization, in Quartzarenic Neosol, and the root system development of _Urochla_ plants found that higher phosphorus doses resulted in an average increase of 172.5% in root mass [30]. Similarly, in a study conducted on Dyn-trophic Red Latosol, testing phosphorus doses (0.0, 277.5, 555.0, 832.5, and 1110.0 kg ha\({}^{-1}\) of single superphosphate) for dry matter yield in maize, greater production was observed at higher doses [31]. This increased plant growth and production with higher phosphorus supply is attributed to more efficient root development, enhancing water and nutrient uptake due to a larger soil exploration area. This leads to better phosphorus distribution in the plant, allowing its translocation and storage in superficial roots and aerial parts [32]. In this context, increasing soil P levels enhances dry matter production in crops, particularly in pastures, due to their dependence on this nutrient for tillering and root development [33]. However, in the present study, no significant yield difference was observed between the control (0 kg ha\({}^{-1}\)) and the highest residual dose (240 kg ha\({}^{-1}\)) (Tables 3 and 22). This can be attributed to the area being under a stabilized no-till system for 20 years, with a diverse crop rotation, involving plants with different root types, sizes, and nutritional requirements. Consequently, this increases nutrient cycling efficiency, as nutrients are absorbed at different soil depths, accumulated in plant tissues, and redeposited into the soil after mineralization, meeting the crop's phosphorus needs [34]. The bacterium _A. brasilense_ colonizes the interior and surface of roots as facultative endophytic diazotrophs. In addition to fixing nitrogen, it can also promote plant growth by solubilizing phosphate, producing phytohormones (auxins, gibberellins, and cytokins), and stimulating root metabolism [35]. This microorganism benefits grasses by primarily enhancing root development, which, in turn, improves soil surface utilization for water and nutrient absorption [36]. These findings support previous research showing that _A. brasilense_ facilitated the development of Cynodon (Croastcross) plants during the summer of the second production year, after one year of application [37]. However, in the present experiment, the presence or absence of _A. brasilense_ did not significantly affect Paiaguas grass yield (Table 3). This effect may have been due to the substantial organic residue accumulation after harvest, resulting from the long-term adoption of no-till farming. The abundance of organic material in the soil provides sufficient nutrients for proper crop development [38]. Phosphorus deficiency leads to reduced plant productivity and stature. In soybeans, it lowers the species' potential during early reproductive stages by reducing flower production and increasing flower abortion [39]. However, in the present study, no grain yield differences were observed among treatments with different residual phosphorus applications (Table 4). However, as observed in Figure 7, in the area without inoculation, there was a significant quadratic response of soybean grain yield to the residual phosphorus rates, with an ideal dose of 151.6 kg ha\({}^{-1}\) of P\({}_{2}\)O\({}_{5}\). In contrast, in the inoculated areas, no regression adjustment was observed, indicating that in the absence of inoculation, phosphorus doses influenced soybean yield. In a study by [39], phosphate fertilization resulted in a quadratic adjustment for soybean yield, increasing at lower doses and declining at higher P\({}_{2}\)O\({}_{5}\) doses. This partially aligns with the present study's results, where, despite the lack of a regression fit, a similar trend was observed due to the residual effect of P\({}_{2}\)O\({}_{5}\) doses.