Core Ideas Urochloa brizantha as cover crop produced more biomass and nutrient cycling than U. ruziziensis. Nitrogen fertilizer on Urochloa cover crops increased biomass production but limited maize yield. The highest maize yields were obtained when N was applied on day before seeding or under conventional method (N applied at seeding plus sidedressing). All N applied on Urochloa residue prior to maize can be an option, but is risky in regions of high rainfall. Crop residue decomposition is slower in no‐till (NT) systems, especially in high‐biomass systems. Adopting optimum nN management can provide increased soil coverage and synchronize the supply of nutrients with the period of highest crop demand in agroecosystems. A three‐year experiment was conducted to assess the feasibility of applying N on forage grass cover crops before termination {Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. Ex A. Rich) Stapf] and Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins [syn. B. ruziziensis (R. Germ. and C.M. Evrard)]}, or on forage grass cover crop residues immediately before maize (Zea mays L.) seeding, aiming to supply N to the following maize crop. Urochloa brizantha had 25% higher biomass production and a higher amount of nutrient content than U. ruziziensis. The N application before termination increased biomass production and nutrient content in cover crop residues compared with the conventional fertilization method (30 kg N ha−1 in the maize seeeding plus 170 kg N ha−1 sidedressed in V6 growth stage). Nitrogen applied one day before seeding (DBS) of maize or using conventional method resulted in a higher number of ears per plant and more kernels per ear as well as a higher grain yields of maize (13.8 and 14.1 Mg ha−1, respectively) compared to N applied on cover crops. Our results suggest that, while both forage grass cover crops produced greater amounts of dry matter (DM) and released similar amounts of nutrients, applying all N to cover crops before maize is not a feasible alternative. Nitrogen application 1 DBS could be an alternative management option to supply N to maize because this method resulted in similar nitrogen use efficiency (NUE) as conventional fertilization method.

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High grain yields of upland rice (Oryza sativa L.) can be achieved in no-tillage systems. However, managing nitrogen (N) fertilization for rice in succession to forage grasses is a challenge because forage residues change N cycling and increase microbial immobilization of N, thereby reducing N availability to the subsequent cash crop. In the present study, two field experiments were conducted to determine if applying all or part of the N fertilizer on preceding palisade grass (Urochloa brizantha) and ruzigrass (Urochloa ruziziensis) or their desiccated residues immediately before rice seeding can supply N to the subsequent rice crop. Forage biomass yield (8–16 Mg ha− 1), N accumulation, and N supply to the subsequent upland rice were highest when all of the N fertilizer was applied on forage grasses at 50, 40 or 35 days before rice seeding (DBS), as opposed to the conventional split application at rice seeding and at tillering. On average, the grain yield of upland rice was 54% higher in succession to palisade grass compared with ruzigrass. The grain yield of rice was higher when N was applied to palisade grass at 35 DBS and ruzigrass at 50 DBS, reaching 5.0 Mg ha− 1 and 3.7 Mg ha− 1, respectively. However, applying N to ruzigrass was less effective for increasing upland rice yields since the yields did not differ from the treatments with the conventional split application. Adjusting the time of N application to forage grasses to increase the grain yields of subsequent upland rice is a sustainable alternative that can promote the economic viability of upland rice production.

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Common bean (Phaseolus vulgaris L.) has been grown under no‐till (NT), but nitrogen (N) management remains unclear when a previous cover crop is part of the farming system. In this study, we hypothesized that N applied to living cover crops, preceding the main grain crop of the rotation, can increase productivity and N‐use efficiency of the grain crop. Common bean was grown after palisade grass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster] and ruzigrass [Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins] cover crops combined with N management [application to living cover crops 35 days before common bean seeding (DBS), 1 DBS, conventional, and control (zero‐N application)] in four experiment‐years. Dry matter (DM) and N content for palisade grass was consistently greater at termination relative to ruzigrass. Nitrogen application 35 DBS increased cover crop DM, N content, and the decomposition rate relative to the other N treatments. Greater common bean yield occurred following palisade grass than ruzigrass, and N application 35 DBS increased common bean yield compared to 1 DBS and conventional in one out of four experiment‐years. Only minor differences in the agronomic efficiency (AE) of applied N to cover crops were detected between 35 DBS and 1 DBS, and only for one experiment‐year, when palisade grass resulted in greater AE than ruzigrass. Applying N early to living crops such as palisade grass is an alternative N management strategy to the traditional approach for N fertilization in common bean.