The effects of a combination of returned straw and different N fertilizer application rates on the physical and chemical properties of lime concretion black soil and crop yields were systematically studied, based on data from a four year experiment using a winter wheat-summer maize rotation system in Mengcheng City, Anhui Province, China. The results showed that the bulk density of surface soil under areas where straw was either incorporated or removed were 1.14-1.20 g/cm³ and 1.24-1.31 g/cm³, respectively. Straw incorporation decreased soil density by 2.5%-9.2%, while soil water content and water storage increased over the four years by 8.2%-28.5% and 4.1%-19.9%, respectively, after the return of the straw. The total soil porosity and capillary soil porosity in the areas of returned straw treatments ranged from 3.0%-57.1% and 33.9%-41.0%, respectively, whilst the same parameters ranged from 50.7%-54.6% and 27.3%-29.5%, respectively, under the areas where straw was removed. In contrast, non-capillary porosity decreased by 6.4%-38.8%, showing a significant difference between areas where straw was incorporated or removed. The nitrate nitrogen content of top soil under the returned straw treatment areas was significantly increased by 9.80%-86.71% greater than that of the areas where straw was removed, especially with N application rates of 540, 630, and 720 kg N hm^-2 a^-1. Nitrogen accumulation in surface soil for N application rates of 360, 450, 540, 630 and 720 kg N hm^-2 a^-1 were 1.42, 1.53, 2.22, 2.51 and 2.12 times that of areas where no fertilizer was added, respectively, for the returned straw areas and 1.24, 1.38, 1.53, 1.59, 1.72 times the no added fertilizer accumulation for the area where straw was removed. For both straw incorporated areas or not, there were exponential relationships between the nitrate nitrogen content and N application amount, although the correlation coefficient was higher under the straw incorporation treatments than for those where straw was removed. Compared to nitrate, the ammonia nitrogen content showed no obvious differences between areas of straw incorporation and removal. Ammonia accumulation under different N application rates was affected by straw addition. Under straw return treatments, it increased exponentially with the increase of N application rates, and decreased exponentially under areas where straw was removed, but there was no significant correlation. The effects of straw incorporation and N application rates on maize and wheat yields were different. For maize, the yield gradually increased from 360 kg N hm^-2 a^-1 to 720 kg N hm^-2 a^-1of N application levels under both straw added areas and straw removed areas. However, the wheat yield gradually increased from 360 kg N hm^-2 a^-1 to 450 kg N hm^-2 a^-1 and from 360 kg N hm^-2 a^-1 to 630 kg N hm^-2 a^-1, and decreased when N exceeded 450 kg N hm^-2 a^-1and 630 kg N hm^-2 a^-1 under areas of straw removal and straw incorporation. The high yields of maize and winter-wheat with straw incorporation treatments would be obtained under the N application rates of 696, 630 kg N hm^-2 a^-1, respectively. N application rates of 579, 627 kg N hm^-2 a^-1 in straw removal areas would obtain high yields, but they were lower than that from areas of returned straw treatments. The force analysis showed that returning straw was the most important influencing factor of soil physical properties, and both straw incorporation and N application rates can compact crop yields, but the force of N level to yield is stronger than that for returning straw.