Corrected data following equation (*x* + 0.5)0.5.

ΨMeans followed by the same letters in the column do not differ by Tukey at 0.05 probability level.

**Table 6.** Nitrogen utilization efficiency (NUE), recovery of the applied nitrogen (RAN), physiological efficiency (FE), and agronomic efficiency (AE) in the function of N rates and sources and inoculation with *Azospirillum brasilense* in the wheat crop.

The Effect of N Fertilization on Wheat under Inoculation with *Azospirillum brasilense* http://dx.doi.org/10.5772/intechopen.68904 177

**Figure 5.** Nitrogen utilization efficiency (NUE) in wheat crop in the function of N rates. Selvíria—MS, Brazil 2015.

In relation to the N sources, urea presented higher NUE compared to Super N, differently from what was expected due to the possibility of mitigation of volatilization of the ammonia provided by Super N fertilizer (urea with urease enzyme inhibitor NBPT) (**Table 6**). However, Dupas et al. [53] evaluated in the *Brazilan Cerrado* the dry‐matter yield, RAN, and NUE of palisade grass in response to sources of N (ammonium nitrate, ammonium sulfate, ammonium sulfate‐nitrate, urea, urea with urease inhibitor NBPT, polymer‐coated urea, and control) in seven harvests (100 kg ha−1 N applied after each harvest) and reported for RAN and NUE that the use of N fertilizers that minimizes N loss, such as urea with urease inhibitor NBPT, and polymer‐coated urea, was very promising, especially for minimizing the environmental impact of N fertilization. However, they found no difference in DMY due to N sources.

The inoculation with *A. brasilense* did not influence the NUE, although it gave 15.4% greater efficiency compared to the non‐inoculated treatments (**Table 6**), which again may be indicative of the phytohormonal effect cited in the literature, confirming that *Azospirillum* produces phytohormones that stimulate root growth of several plant species and that this greater development of the roots may be implied in several other effects, such as increases in the water and nutrient uptakes like N.

The interaction between N rates and inoculation, and N sources and inoculation, was significant for RAN. Analyzing the split between N rates and inoculation, at 50 and 100 kg ha−1 of


Selvíria—MS, Brazil 2015.

this bacteria diazotrophic may vary and determine the success or failure of *A. brasilense*

The NUE was negatively affected by the increment of N rates with adjustment to the linear function decreasing (**Table 6**, **Figure 5**). This result can be attributed to the losses of N portrayed clearly in the literature. The increase of N rates culminates in greater losses and less use by the crops, since there is a limit in the nutritional demand of the plant, that is, the plants uptake certain amount of nutrients for a given time; thus, the N that is applied and is not taken can be lost, decreasing the efficiency of fertilization with the higher rates of N, as portrayed in the literature by the law of decreasing increments. The results are similar to those reported by Silva et al. [51], studying N rates (0, 100, 200, and 300 kg ha−1) in the Marandu palisadegrass and Sant'Ana et al. [52], working with common bean crop in the rates of 0, 30,

> **NUE RAN FE AE (kg kg−1) (%) (kg D.M. kg−1 of N**

0 – – – – 38.34 78.82 50.27 22.41 30.07 62.08 48.90 14.57 13.92 31.08 55.24 8.40 15.30 39.52 39.00 6.79

Urea 29.65 a 56.87 51.63 aΨ 14.14 Super N 19.16 b 48.87 45.08 a 11.95 L.S.D. (5%) 6.51 12.78 16.97 3.05

With *Azospirillum* 26.15 a 63.11 42.01 a 16.58 Without *Azospirillum* 22.67 a 42.64 54.70 a 9.50 L.S.D. (5%) 6.51 12.78 16.97 3.05 Overall mean 24.41 52.87 48.35 13.04 C.V. (%) 17.25# 15.33# 19.44# 24.24#

ΨMeans followed by the same letters in the column do not differ by Tukey at 0.05 probability level.

**Table 6.** Nitrogen utilization efficiency (NUE), recovery of the applied nitrogen (RAN), physiological efficiency (FE), and agronomic efficiency (AE) in the function of N rates and sources and inoculation with *Azospirillum brasilense* in the

**accumulated)**

**(kg grains kg−1 N applied)**

inoculation.

176 Nitrogen in Agriculture - Updates

**N rates (kg ha−1)**

**N sources**

**Inoculation**

#

wheat crop.

Selvíria—MS, Brazil 2015.

Corrected data following equation (*x* + 0.5)0.5.

60, 120, and 240 kg ha−1 of N in topdressing.
