The loss of N in farmland is an important cause of agricultural non-point source pollution, which seriously impacts the aquatic environment.  A two-year (2017–2018) experiment was conducted to investigate the characteristics of runoff and N losses under different tillage practices.  Taking downslope ridge planting and cross ridge planting as the experimental treatments, the characteristics of surface runoff, interflow, and N losses in sloping farmlands with yellow soil were studied throughout the maize growth period.  As the rainfall increased, the surface runoff and interflow also increased.  The surface runoff and N losses in the surface runoff of downslope ridge planting were significantly higher than those of cross ridge planting.  The interflow volumes and N losses in the 0–20 and 20–40 cm soil layers of the cross ridge planting were significantly higher than those of the downslope ridge planting.  The total N (TN) losses from surface runoff accounted for 54.95–81.25% of the N losses from all pathways.  Therefore, we inferred that surface runoff is the main pathway of N losses.  Dissolved total N (DTN) was the main form of N loss under different tillage measures, as it accounted for 55.82–94.41% of the TN losses, and dissolved organic N accounted for 52.81–87.06% of the DTN losses.  Thus, we inferred that dissolved N is the main form of N loss.  Future research must focus on the prevention and control of the N losses during the maize seedling stage to reduce the environmental pollution caused by ammonium N through runoff.

To optimize the spatial distribution of cotton bolls and to increase the yield, the relationship between yield components and boll spatial distribution was investigated among different Bt (Bacillus thuringensis) cotton varieties.  A five-year field experiment was conducted to reveal the reasons for the differences in lint yield and fiber quality across three Bt cotton varieties with different yield formations from 2013 to 2017.  The lint yield of Jiman 169 (the average yield from 2013–2017 was 42.2 g/plant) was the highest, i.e., 16.3 and 36.9% higher than Lumianyan 21 (L21) and Daizimian 99B (99B), respectively.  And the differences in boll weight among the three cultivars were similar to the lint yield, while the others yield components were not.  So the increase in lint yield was mainly attributed to the enlargement in boll weight.  However, the change in fiber quality was inconsistent with the lint yield, and the quality of L21 was significantly better than that of Jimian 169 (J169) and 99B, which was caused by the diversity of boll spatial distribution.  Compared with 99B, the loose-type J169 had the highest number of large bolls in inner positions; the tight-type L21 had a few large bolls and the highest number of lower and middle bolls.  And approximately 80.72% of the lint yield was concentrated on the inner nodes in Jiman 169, compared with 77.44% of L21 and 66.73% of 99B during the five-year experiment.  Although lint yield was significantly affected by the interannual changes, the lint yield of J169 was the highest and the most stable, as well as its yield components.  These observations demonstrated the increase in lint yield was due to the increase in boll weight, and the large bolls and high fiber quality were attributed to the optimal distribution of bolls within the canopies.