The low availability of phosphorus in most Brazilian soils causes a heavy dependence of agricultural production on phosphate fertilizers, which are generally agronomically inefficient in tropical soils. Breeding for increased longevity of sugarcane ratoons is extremely important, but understanding how the efficiency of phosphate fertilization can be improved is equally necessary. The objective of this research was to evaluate the effects of phosphate fertilizers with and without polymer coating on the productivity and nutritional status of sugarcane ratoons and phosphorus availability in the soil. The experiment was carried out on a commercial sugarcane field on a dystrophic Ultisol over two growing seasons in a randomized complete block design with four replications. Two phosphorus sources (monoammonium phosphate (MAP) and MAP + Policote) were tested at four rates (20, 40, 60 and 80 kg P₂O₅ ha⁻¹) in addition to the control (no P fertilization). The Policote-coated phosphate fertilizer induced higher stalk and TRS yields in the first experimental year, while the same effect was not observed in the second year. Nevertheless, with the reapplication of the treatments in the second study year, the mean stalk yield was high in response to the application of 20 kg P₂O₅ ha⁻¹ of coated fertilizer and very different from that of the higher rates of the same fertilizer, which yielded 88 Mg ha⁻¹, i.e., 8 Mg ha⁻¹ more than the mean of the other rates.

The objective of this study was to evaluate dry matter (DM) production of Urochloa brizantha cv. Marandu and ammonia volatilization in response to rates and sources of enhanced-efficiency N fertilizers. The experiment was took place in a pasture area, two growing seasons. A randomized block design with four replications was used, in a 4 × 2 + 1 factorial arrangement, consisting of four N sources (Urea—Ur_Conv; Ammonium nitrate—AN; Urea + NBPT—Ur_NBPT; Urea + Duromide—Ur_Duromide) and two nitrogen rates (100 and 200 kg ha⁻¹ year), plus a treatment without nitrogen fertilization (control). At both N rates, ammonia volatilization from Ur_Conv100/200 was greatest. Ammonia volatilization was less after Ur_NBPT and Ur_Duromide application, with values similar to AN. Ammonia losses from Ur_Duromide tend to be lower than from Ur_NBPT. The N use efficiency in dry matter production of Marandu was influenced by the N sources and rates. At both N rates, the efficiency of Ur_Duromide and Ur_NBPT was greater than that of Ur_Conv. With regard to total DM and leaf percentage in response to N rates, DM production increased after 200 kg N ha⁻¹ rates in response to all sources, in both years. The Ur_Duromide reduce N losses by volatilization compared to Ur_NBPT and Ur_conv, and resulted in greater total DM production and relative leaf production of Marandu, in comparison to Ur_NBPT, AN and Ur_conv.

O presente estudo foi conduzido com o objetivo de avaliar a produção de massa seca da parte aérea e teor de proteína bruta da pastagem de Urochola brizantha cv. Marandu, além das perdas de amônia (N-NH3) por volatilização e a eficiência da adubação de fontes de fertilizantes nitrogenados e doses de nitrogênio aplicadas. O delineamento experimental foi em blocos casualizados, com quatro repetições, em esquema fatorial 3x3, os tratamentos consistiram na combinação de três fontes de nitrogênio (ureia, ureia com polímero e ureia com inibidor de urease NBPT (N-(n-butil) tiofosfórico triamida), três doses de N (50,100 e 150 kg ha-1 de N) e o controle (sem adubação) constituindo 10 tratamentos, com quatro repetições. A fonte nitrogenada que apresentou menores perdas de amônia (N-NH3) por volatilização foi a ureia tratada com inibidor de urease (NBPT), o pico de volatilização ocorreu no segundo dia após a aplicação do nitrogênio. As doses de N influenciaram a PMS, PB e volatilização da amônia, sendo assim, devem ser considerados na determinação de estratégias no manejo da pastagem.

Aims The objective of this study was to evaluate dry matter (DM) production of Urochloa brizantha cv. Marandu and ammonia volatilization in response to rates and sources of enhanced-efficiency N fertilizers. Methods The experiment was installed in a pasture area, evaluated over two growing seasons. A randomized block design with four replications was used, in a 4x2+1 factorial arrangement, consisting of four N sources (Urea - Ur Conv ; Ammonium nitrate - AN; Ureia+NBPT - Ur NBPT ; Urea+Duromide - Ur Duromide ) and two nitrogen rates (100 and 200 kg ha -1 year), plus a treatment without nitrogen fertilization (control). Results At both N rates, ammonia volatilization from Ur Conv100/200 was highest. Ammonia volatilization was lower after Ur NBPT and Ur Duromide application, with values similar to AN. Ammonia losses from Ur Duromide tend to be lower than from Ur NBPT . The N use efficiency in dry matter production of Marandu was influenced by the N sources and rates. At both N rates, the efficiency of Ur Duromide and Ur NBPT was greater than that of Ur Conv . With regard to total DM and leaf percentage in response to N rates, DM production increased after 200 kg N ha -1 rates in response to all sources, in both years. Conclusions The Ur Duromide reduce N losses by volatilization compared to Ur NBPT and Ur conv, and resulted in greater total DM production and relative leaf production of Marandu, in comparison to Ur NBPT, AN and Ur conv.