Nitrogen fertilisation improves the grain production efﬁciency and sustainability of out-of-season corn and Congo grass intercropping Karina Batista A,B , Alessandra Aparecida Giacomini A , Luciana Gerdes A , Waldssimiler Teixeira de Mattos A , and Ivani Pozar Otsuk A A Instituto de Zootecnia, Agência Paulista de Tecnologia dos Agronegócios, 56 Heitor Penteado St. Centro, Zip Code: 13.460-000, Nova Odessa, SP, Brasil. B Corresponding author. Email: batistakarin@gmail.com Abstract. Intercropping is a method for straw production and maintenance during the dry season in no-tillage systems. Among the crops used for intercropping are corn and grasses. However, nitrogen can interfere with the production capacity of these plants. The objective of this study was to evaluate the macronutrient accumulations and efﬁciency values of out-of-season corn and Congo grass intercropped under a no-tillage system as a function of the nitrogen fertilisation applied by side dressing. The experimental design was a randomised complete block with four replicates of four nitrogen application rates: 0, 30, 60 and 90 kg ha 1 . The evaluations were carried out when the corn was physiologically mature. The phosphorus and potassium accumulation and nitrogen utilisation efﬁciency of the out-of-season corn did not respond to the nitrogen rates. The nitrogen recovery efﬁciency and the nitrogen to biomass conversion efﬁciency of the Congo grass also did not respond to nitrogen application rates. Nitrogen fertilisation as side dressing in the rows of the out-of- season corn and Congo grass intercropping improves the nutrient cycling in the no-tillage system. Side dressing fertilisation with nitrogen improves the agronomic efﬁciency and physiological efﬁciency of the out-of-season corn and Congo grass intercropping under a no-tillage system. Additional keywords: crops, integrated system, no-tillage, out-of-season, sustainability. Received 4 January 2019, accepted 13 March 2019, published online 14 May 2019 Introduction One of the methods for the production and maintenance of straw in the dry season no-tillage system is the system of agriculture integrated with forage production, in which intercropping is used. Intercropping is a cropping system that involves planting two or more species in an area, such that each crop can coexist with the other throughout at least part of its cycle (Gou et al. 2018). For intercropping between grain plants and forage under a no-tillage system, it is essential to understand the dynamics and balance of nutrients to adjust agronomic practices and increase the efﬁciency of the intercropped plants without compromising their nutritional quality (Ciampiatti et al. 2013). Among the crops used for intercropping are out-of-season corn (Zea mays) and Congo grass (Urochloa ruziziensis cv. Comum), which are used as a strategy to protect soil and reduce the effects of monocultures in autumn–winter seasons (Pacheco et al. 2011). Brazilian out-of-season corn is an important economic alternative to autumn–winter seasons tillage. However, in order to achieve high economic productivity, it removes large amounts of nitrogen and requires adequate management of nitrogen levels to complement the amount of soil nitrogen and reduce unnecessary expenses with the purchase of nitrogen fertiliser (Souza et al. 2011). Although there has been an increased development of cropping systems in recent years, the world’s fertiliser recommendations for corn are still based on a single crop, and additional studies relevant to intercropping are required (Martins et al. 2017). Congo grass has been used for intercropping in the autumn–winter seasons because of its tolerance to water deﬁciencies, slow initial growth and accumulation of dry mass and nutrients only after the beginning of the rains in September and October (Pacheco et al. 2011). In Congo grass, nitrogen availability deﬁnes the plant’s production capacity throughout its phenological cycle, because of its participation in the growth and development of plant tissues (Salvador et al. 2016). The use of Congo grass intercropped with out-of-season corn for straw production and maintenance of the no-tillage system needs to be adequate, since the success of this system is related to the decomposition dynamics of vegetable residues. This is especially important during the ﬁrst years of the no-tillage system when the lowest rate of decomposition of organic matter in the soil can result in nitrogen deﬁciencies (Kihara et al. 2011). The dynamics of nitrogen and its availability in the soil–plant system may interfere with its efﬁcient use (Fageria and Baligar 2005). To combat overuse or deﬁciency in nitrogen Journal compilation Ó CSIRO 2019 www.publish.csiro.au/journals/sr CSIRO PUBLISHING Soil Research, 2019, 57, 397–407 https://doi.org/10.1071/SR19002