Pasture and grain crop intercropping is considered an alternative for increasing biomass production during the winter periods in Brazil for the establishment of no-tillage systems. We studied nitrogen (N) fertilization rates in a corn-palisadegrass intercropping system that would allow both corn and biomass production without a reduction in corn yield. A field trial was carried out in São Desidério, Bahia -Brazil using a complete block experimental design with a 5 x 2 factorial layout with two factors: N rate (control, 50, 100, 150, and 200 kg ha -1 N) and two cropping systems (corn with or without palisadegrass). Both corn and palisadegrass were sown simultaneously with N fertilizer applied at sowing. The measurements included corn biomass, grain yield and N uptake. In addition, palisadegrass biomass was assessed at corn harvest and at three consecutive times during the winter. There was an interaction between N rates and the intercropping system. Grain yield was affected by intercropping when N fertilizer rates were lower than 100 kg ha -1 , but above that rate, corn grain yield reached 10,000 kg ha -1 and was similar with or without palisadegrass. Nitrogen fertilizers also positively affected corn N uptake. There was no residual effect of N fertilization on palisadegrass biomass production during the sampling periods. However, the biomass of the palisadegrass increased during the winter period and reached 5,000 kg ha -1 of dry matter by the following season. There was no corn yield reduction when corn was intercropped with palisadegrass using nitrogen rates above 100 kg ha -1 . In addition, it is possible to increase biomass production for the establishment of no-tillage systems in Brazil.

Early fertilizer nitrogen (N) application on cover crops or their residues during the off-season is a practice adopted in Brazil subtropical conditions under no-tillage corn (Zea mays L.) systems. However, the effect of early N application on yield, plant N content, and N recovery efficiency (NRE) for corn is not yet well documented. Five fertilizer N timings in an oat-corn system were evaluated in two studies utilizing an isotopic-labeled N determination, 15N isotope. The N fertilization timings were: (i) oat tillering, (ii) 15 days before corn planting time, over the oat residues, (iii) at corn planting time, (iv) in-season at the three-leaf growth stage (V3), and (v) in-season split application at V3 and six-leaf (V6) growth stages. Based on the statistical analysis, the N fertilization timings were separated into three groups: 1) N-OATS, designated to N applied at oat; 2) N-PLANT, referred to pre-plant and planting N applications; and 3) N-CORN, designated to in-season corn N applications. Corn yield was not affected by the N fertilization timing. However, the N-CORN N fertilization timings enhanced NRE by 17% and 35% and final N recovery system (plant plus soil) by 16% and 24% all relative to N-OATS and N-PLANT groups, respectively. Overall, N-OATS resulted in the largest N derived from fertilizer (NDFF) amount in the deeper soil layer, in overall a delta of 10 kg N ha-1 relative to the rest of the groups. Notwithstanding corn yield was not affected, early N fertilization under subtropical conditions is not a viable option since NRE was diminished and the non-recovery N increased relative to the in-season N applications.

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The corn biomass and nutrient dynamics may be altered when it is intercropped with Brachiaria (syn. Urochloa spp.). The present study aimed to investigate the dynamics of biomass, nitrogen (N), phosphorus (P) and potassium (K) for farming systems that produce corn intercropped with Brachiaria species. Field experiments were performed during the season and off-season, in a split-plot design. The main plots were composed of Brachiaria species (B. brizantha,B. ruziziensis and B. Convert) intercropped with corn, in addition to corn monocropping. The subplots consisted of three forage sampling periods, ranging from 0 to 60 days after the corn harvest. The intercropping arrangements did not affect the corn grain yield, nutrient accumulation and partitioning, relatively to the corn monocropping. After the grain harvest, B. brizantha achieved the greater biomass accumulation rate in both the season (69 kg ha-1 day-1) and off-season (17 kg ha-1 day-1). The nutrient accumulation ranged widely between the Brachiaria species and planting seasons: 0.2-1.2 kg ha-1 day-1 for N; 0.01-0.07 kg ha-1 day-1 for P; and 0.13-0.8 kg ha-1 day-1 for K. However, the greatest nutrient accumulation was found for B. brizantha, followed by B. ruziziensis and then B. Convert. In the short-term, corn intercropped with Brachiaria in the season showed the largest effect on the nutrient cycling and biomass yield. The intercropping between corn and B. brizantha in the season was the best way to enhance the biomass yield and the N, P and K cycling.

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