RESEARCH ARTICLE Efficient Nitrogen and Water Management for the Soybean– Wheat System of Madhya Pradesh, Central India, Assessed Using APSIM Model M. Mohanty • K. Sammi Reddy • M. E. Probert • R. C. Dalal • Nishant K. Sinha • A. Subba Rao • N. W. Menzies Received: 5 March 2014 / Revised: 6 August 2014 / Accepted: 25 September 2014 Ó The National Academy of Sciences, India 2014 Abstract A series of long-term simulations were carried out to investigate alternative management practices to increase grain yields of soybean and wheat by optimizing sowing dates, nitrogen (N) and water requirements, along with complimenting farmyard manure (FYM) as a N source in the soybean–wheat cropping system of Madhya Pradesh. The APSIM simulation study showed that the mean soy- bean yield ranged from 1.0 to 1.6 t ha -1 for the different dates of sowing. The average wheat grain yield was 3.2–3.9 t ha -1 , whereas, the crop sown on 15 November gave the highest yield. In this region, there is a potential to increase soybean and wheat yields by 0.6 and 2.2 t ha -1 , respectively. Among the various irrigation practices sim- ulated, five irrigations of 60 mm at 20 days interval was the best option for wheat. Application of 16 t FYM ha -1 to soybean produced 50 % higher wheat yield than the same amount of FYM applied to wheat. The wheat yield obtained from inorganic application of N was at par with that obtained from the application of integrated and organic sources. However, the amount of N loss from the integrated use of fertilizer N was lower than that from the current recommended practice for the region. Application of FYM alone or in combination with inorganic fertilizer main- tained higher soil organic carbon concentration as com- pared to the application of inorganic fertilizer alone. Thus, the model provided a mean of evaluating alternative crop N and water management options for effectively managing the soybean–wheat cropping system. Keywords Soybean Á Wheat Á Nitrogen Á Farmyard manure Á Modelling Á APSIM Introduction Soybean is the major rainy season crop in the rainfed agro- ecosystem of central and peninsular India [1]. The crop is predominantly grown on Vertisols and associated soils with an average crop season rainfall of about 900 mm. Soybean occupies third place in the oilseed production in India, after groundnut (Arachis hypogaea) and rape seed (Brassica napus)/mustard (Brassica juncea) and the area under soy- bean cultivation in India has increased from 0.03 mil- lion ha in 1970 to 10.7 million ha in 2012 [2]. Introduction of soybean in these areas has led to a shift in the cropping system from rainy season fallow followed by post rainy season wheat or chickpea (fallow-wheat/chickpea), to soybean followed by wheat or chickpea (soybean–wheat/ chickpea). Soybean/wheat as a legume-cereal cropping system has proved to be the most productive and profitable system of central India. Besides improving the socio-economic con- ditions of small and marginal farmers of this region, M. Mohanty Á N. W. Menzies School of Agriculture and Food Science, The University of Queensland, St Lucia, QLD 4072, Australia M. Mohanty Á N. K. Sinha (&) Á A. Subba Rao Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal 462038, India e-mail: nishant.sinha76211@gmail.com K. Sammi Reddy Central Research Institute for Dryland Agriculture, Santosh Nagar, Hyderbad, India M. E. Probert CSIRO Ecosystem Sciences, Dutton Park, QLD 4102, Australia R. C. Dalal Department of Science, Information and Technology, Innovation and the Arts, Dutton Park, QLD 4102, Australia 123 Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci. DOI 10.1007/s40011-014-0443-3