Nitrous Oxide Emissions from a Long-Term Integrated Crop–Livestock System with Two Levels of P and K Fertilization

Nitrous oxide (N 2 O) emissions resulting from nitrogen (N) fertilization have been documented. However, no data on the effects of other nutrients, such as phosphate (P) and potassium (K), on N 2 O emissions in integrated crop–livestock systems are available so far. In the 2015/2016 and 2016/2017 growing seasons, we measured N 2 O emissions from a long-term system, established in 1991 in the Cerrado biome (a tropical savanna ecoregion in Brazil), fertilized with two P and K levels. The studied no-tillage farming systems consisted of continuous crops fertilized with half of the recommended P and K rates (CC-F1), continuous crops at the recommended P and K rates (CC-F2), an integrated crop–livestock system with half of the recommended P and K rates (ICL-F1), and an integrated crop–livestock at the recommended P and K rates (ICL-F2). The cumulative N 2 O emissions (603 days) and soil chemical properties were analyzed as a 2 × 2 factorial design (long-term agricultural systems x fertilization). The cumulative N 2 O emissions from CC-F2 and ICL-F1 were 2.74 and 1.12 kg N ha −1 , respectively. The yield-scaled N 2 O emissions from soybean were 55.5% lower from ICL-F1 than from CC-F2 in the 2015/2016 growing season. For off-season sorghum, the mean yield-scaled N 2 O emissions were 216 mg N 2 O m −2 kg −1 (in a range from 79.83 to 363.52 mg N 2 O m −2 kg −1 , for ICL-F2 and CC-F1, respectively). The absence of pasture and the presence of soybean and sorghum promoted the highest cumulative N 2 O emissions, favored by the recommended rate in relation to half of the P and K. In the total evaluation period (603 days), the presence of grazed land in the years prior to this study and land fertilized with half the recommended P and K rates in an integrated crop–livestock system reduced the resulting cumulative N 2 O emissions by 59%. Thus, we conclude that crop–livestock systems can be beneficial in reducing P and K applications and also in mitigating N 2 O emissions in comparison with continuous cropping systems fertilized with the full recommended P and K rates. In view of the global fertilizer crisis, this aspect is extremely relevant for agriculture in Brazil and around the world.