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Preceding crop and nitrogen (N) fertilization affect N cycling and productivity of subsequent wheat in double cropping. However, the effects of preceding crop and N fertilization on relationships between yield and “mineral nutriome” or nutritional quality (amount and bioavailability) in wheat grains have not been well characterized, particularly not in the case of multiple mineral nutrient elements and when considering cumulative effects of fertilization strategies in long-term field experiments. Here we present effects of preceding crop (monocultures of maize, peanut or soybean, and intercropping of maize with peanut or soybean) at 4 levels of annual fertilizer N input (0–440 kg/ha) on yield traits, major mineral nutrients and their relationships in wheat grains in a 4-years continuous double-cropping field experiment in the North China Plain. Nitrogen fertilizer increased wheat grain yields, mass concentrations of N and copper (Cu), and micronutrient (mainly zinc: Zn and iron: Fe) bioavailability, while no N supply was associated with low grain yield, N and Cu concentrations and micronutrient bioavailability, high mass concentrations of Zn, manganese, phosphorus (P), calcium, magnesium and phytate-P, and a high ratio of phytate-P/P. Moderately lowering N input from the in-season 240 to 200 kg/ha (but not 120 kg/ha) would not harm grain yield and most nutritional traits. Compared to significant effects of N application level on almost all grain yield and nutritional traits, and soil properties, preceding crops had less impact and only grain yields and Zn concentrations were significantly affected. Grain yields, N and Zn concentrations varied dramatically from an average of 2.7 to 7.6 t/ha, 16.5–19.3 g/kg and 15.1–19.8 mg/kg with different N application levels, respectively; while varied relatively little from 5.9 to 6.6 t/ha, 17.8–18.3 g/kg and 16.1–18.1 mg/kg under different preceding crops, respectively. Compared to the conventional wheat-maize rotation, a legume pre-crop monoculture but not maize/legume intercropping increased grain yields by 5.0–11.9% on average, but reduced grain Zn concentrations from 17.5–17.8 to 16.1 mg/kg significantly. The legume effect was most significant at zero or low N supply. The relationship between grain yields and Zn concentrations was adequately described by a concave-up parabola (R2 = 0.3001, P < 0.0001, n = 288), suggesting appropriate N fertilization and rotation can achieve high-yield while ameliorating the dilution of grain Zn density. Therefore, our findings provide new insight in relationships among agronomic practices, wheat grain yield and grain nutritional quality (particularly for Zn).

International audience; Pitfall trapping is widely used for studying the abundance and diversity of ground-dwelling arthropods and smallvertebrates. Meta-analysis is a powerful technique to synthesize information across studies, but it requires standardizationto make study results comparable. It has never been studied how results of pitfall trapping should be standardized to obtainestimates of activity-density and diversity that are comparable across studies. We analysed samples of Carabidae(Coleoptera) from annual crops, reported in 104 publications from Europe and North-America, spanning a period of42 years, to find (i) a scaling for pitfall trapping effort to assess activity-density and diversity in pitfall catches across studies; and, (ii) to determine the sources of variability in the catch per unit effort. The total catch was proportional to the number of trap days, with a mean of 1.33 beetles/(trap days). The number of species was allometrically related to the trapping effort defined as the product of the number of traps, their perimeter and the time of exposure in the field. The mean species richness was 7.15 species/(m days)0.25. The size of the catch and the number of species adjusted per unit effort were higher in crops with narrow as compared to wide rows. Other factors were explored but were not influential. There was no significant change in abundance or diversity of carabids in arable land over the 42 years covered. The results give insight in factors affecting carabid abundance and diversity in field studies and enable standardization of pitfall catches across the literature.

The usefulness is discussed of Boer-Ferrari's vegetation-unit classification (S. & F. XX [939]) as an index of yield, use-value, moisture supply and possibly fertility. (Abstract retrieved from CAB Abstracts by CABI’s permission)