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Evaluating the contribution of diverse nitrogen (N) sources in agricultural systems is pivotal for optimizing sustainable farming practices. While knowledge exists about the roles of various N sources, there's limited comprehensive data on the relative contributions of manure compost, fertilizer, and root residues to subsequent plant uptake. A comprehensive field study was conducted in Shandong Province, China, utilizing 15N labeling techniques to clarify these contributions. Four treatments were established, each incorporating four exogenous nitrogen sources (manure compost + urea + maize root + residual urea) applied concurrently at wheat seeding, with only one source being 15N labeled per treatment. Additional two treatments served as controls, one without 15N labelling and another without manure compost. During a wheat growing season, the N contribution from each individual source to subsequent wheat growth was quantified. Manure contributed 10% of the wheat seed N, while urea contributed 18% and maize root contributed 0.3%. Nitrogen recovery in distinct components of the wheat plant (seeds, straw, and roots) was assessed, revealing urea's superior use efficiency within the total wheat biomass at 55%. In contrast, both manure compost and maize root showed a recovery rate of 29%. Although this study spans only one-year, it offers fresh perspectives on the differential contribution and use efficiency of key N sources under field conditions, emphasizing their role in bolstering crop health and productivity for sustainable agriculture. [Display omitted] • Manure contributes 10% of N in wheat seeds, more than maize root (0.3%), but less than urea (18%). • Soil and other contributes 72% of the seed N, 71% of the straw N, and 65% of the root N. • N use efficiency in wheat biomass is comparable for manure and maize root (29%). • Urea shows superior N use efficiency in wheat total biomass at 55%. • Grains per spike, not spike number or grain weight, influence yield differences. [ABSTRACT FROM AUTHOR]

Climate change impacts crop productivity as atmospheric conditions and water supply change, particularly in intensive cropping areas. This study used the validated AquaCrop Model, which was run with downscaled daily climate data produced by SDSM and CanESM2. The changes in the potential grain yield of winter wheat and summer maize and water budget during the cropping seasons were estimated for the Huang-Huai-Hai Plain (3H Plain) under RCP4.5 and RCP8.5 scenarios. The results show that the potential yield of winter wheat is increasing with similar spatial patterns in the 2030s, 2050s, and 2080s, with much of the increase is distributed in Shandong and northeastern parts of Henan. During the winter wheat growth period, the water budget deficit will likely improve from −210 mm in the 2030s to −202 mm in 2080s under RCP4.5 and from −206 mm in the 2030s to −191 mm in 2080s under RCP8.5 across the 3H Plain. The water budget during the winter wheat period will continue to be in deficit in the north 3H Plain and improvements are estimated mostly in the lower southern areas of the Plain. The summer maize potential yield is estimated to increase from the baseline period, but yields will decrease by 0.81%, 1.19%, and 2.10% in the 2030s, 2050s, and 2080s, respectively, under RCP8.5 compared to RCP4.5. During the summer maize growth period, the water budget is also estimated to improve from 109 mm in 2030s to 126 mm in 2080s under RCP4.5 and 107 mm in the 2030s to 163 mm in 2080s under RCP8.5. This increase is mainly estimated in the central and south of the 3H Plain. The estimated ET c of winter wheat shows no significant decrease, while the reduction of 6 mm and 13 mm for summer maize is observed under RCP4.5 and RCP8.5, respectively. The study provides scientific evidence to devise adaptation and mitigation climate change strategies for agricultural productivity and water resource management. • The potential winter wheat yield will increase under RCP4.5 and RCP8.5 scenarios. • The increase in wheat yield follows a similar spatial pattern under both RCP scenarios. • The potential summer maize yield will decrease under RCP8.5 as compared to RCP4.5. • Water deficit for wheat will remain similar to the present with increased temperature. • Water budget during summer will significantly improve in the latter half of this century. [ABSTRACT FROM AUTHOR]