Effects of Plastic Film Mulching on Soil Carbon Fixation Capacity and Fertility Level in Eastern Qinghai

[Objectives]To explore the effects of single application of chemical fertilizers on soil carbon fixation capacity and soil fertility under plastic film mulching conditions in eastern Qinghai,and to provide a theoretical basis for realizing the sustainable development of film mulching planting method in this area.[Methods]The effects of single application of chemical fertilizer cultivation mode under film mulching conditions on the soil organic carbon(SOC),labile organic carbon(LOC),carbon management index(CMI),extractable humus carbon(CHE),humic acid carbon(CHA),and fulvic acid carbon(CFA)in the cultivated layer(0-20 cm)were studied through three consecutive years of field experiments on dryland maize farmland in the eastern Qinghai.[Results]Under the film mulching condition,the SOC,LOC and CMI of the single application of chemical fertilizer cultivation mode were lower than that of the open field control.CHE,CHA and CFA increased with the increase of planting years,but the degree of increase was generally less than that of the open field control.With the increase of planting years,by 2020,the soil LOC/SOC value of film mulching decreased by 4.97%compared with before the start of the experiment,while the open field control increased by 1.11%;the organic carbon oxidation stability coefficient(KOS)of the film mulching was higher than that of the open field control;the soil CHA/CFA value and PQ value were higher than that of the open field control.[Conclusions]Under the condition of single application of chemical fertilizers,the continuous film mulching cultivation mode reduces the soil carbon fixation capacity,and soil organic carbon tends to be stable,which is not conducive to biological utilization and could reduce the soil fertility and degrade the soil quality,causing adverse effects on the stability of crop yield and sustainable production in the long run.

Parity,Timing and Level of Fertility:A Comparative Study on Mean Age at Childbearing in China,Japan and South Korea

Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.After using the decomposition technique to isolate the effects of parity composition and childbearing schedule in each of the three countries,the article presents a quantitative examination of the factors that underlie dynamic changes and cross-national differences of MACs.Results indicate that the MAC of China experienced a decrease between 1990 and 1995,followed by sustained growth afterwards.The increase of MAC in China has been driven by the postponement of childbearing and changes in parity composition,with the former playing a larger role.The mechanisms underlying the patterns since 2010 deserve special attention.Compared with Japan and South Korea,China has had relatively lower MAC during the last 25 years;the three countries demonstrate different patterns in terms of the roles of parity composition and birth timing.The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.

Autoregressive spatial analysis and individual tree modeling as strategies for the management of Eremanthus erythropappus

The objectives of this study were to apply statistical techniques to discriminate fertilization treatments of Eremanthus erythropappus（DC.） Mac Leish.through autoregressive modeling, and to develop individual tree models for diameter and crown area（CA） projection to define management strategies for candeia plantations subjected to different fertilization treatments. This is an important tree species originating from the Brazilian Atlantic Rain forest and Savannah biomes, intensively used in the cosmetic industry. Nonetheless, to date, research has not addressed the management of natural stands or plantations of the species. Our experiment was located in Baependi, Minas Gerais, Brazil, and comprised of four randomized blocks and 13 treatments. The treatments consisted of 12 different regimes of fertilization plus a control. Each sample plot was composed of 50 plants plus two border plants in a planting spacing of 2.5 9 2.0 m and undergoing pruning at 5 and 6 years of age. Starting in the second year, total tree height（H） and circumference（at 1.30 m from the ground or breast height, CBH） were measured every 6 months. Starting in the fifth year CA was measured. Tree growth varied by fertilization strategy.Differences were detected by using an autoregressive approach, considering that standard statistical methods were not powerful enough to detect significant differences.Three growth groups were formed, and maximum growth was obtained for treatment 10（NPK, 8-28-16）. Management guidelines are provided based on individual tree models for different fertilization levels.

Does heat accumulation alter crop phenology, fibre yield and fibre properties of sunnhemp(Crotalaria juncea L.) genotypes with changing seasons?

Field experiments were carried out in split plot design during the dry and wet seasons for two years(two seasons each in 2016–2017 and 2017–2018) with two genotypes(SH4 and SUIN053), two plant geometry(30×15 cm and 45×15 cm main plots) and three levels of NPK(20 kg N ha^(–1), 40 kg P ha^(–1) and 40 kg K ha^(–1);20 kg N ha^(–1), 60 kg P ha^(–1) and 60 kg K ha^(–1);20 kg N ha^(–1), 80 kg P ha^(–1) and 80 kg K ha^(–1)) with an objective to study the relationship between fibre yield of sunhmep and thermal indices. The results indicated that the thermal units such as cumulative heat unit(CHU), photo thermal unit(PTU) and helio thermal unit(HTU) were the highest during dry seasons, while relative temperature disparity(RTD) was the highest during wet seasons irrespective of the genotypes, plant geometry and fertilizer levels. The combined analysis of variance showed that the suitability of sunnhemp genotypes for obtaining fibre and seed yields varied with season. The results further indicated that sunnhemp grew during dry seasons with longer photoperiod and higher values of growing degree days(GDD), HTU and PTU resulted in a higher fibre yield, while a higher seed yield and relatively longer, finer and stronger fibres were obtained during wet seasons with higher RTD values. Regression analysis indicated that CHU was positively related to fibre yield, while RTD was positively related to seed yield. CHU beyond 2 000 °C d reduced seed yield and favoured fibre production. In contrary to CHU, RTD values were positively related to seed yield and negatively related to fibre yield. Similarly, HTU had an inverse relationship with fibre yield while PTU had a positive relationship with fibre yield. The genotype SH4 produced a seed yield of 1 361 kg ha^(–1) during wet seasons, which was significantly higher than SUIN053, while a fibre yield of 990 kg ha^(–1)(significantly higher than that of SH4) was obtained for SUIN053 that required less CHU to attain the phenological events during dry seasons. The per unit area yields of seed and fibre with the closer spacing(30 cm×15 cm) by virtue of higher plant density were 17.0 and 14.9% higher than those with the spacing of 45 cm×15 cm, respectively. Higher doses of P and K resulted in higher seed and fibre yields.

Anammox bacterial abundance and biodiversity in greenhouse vegetable soil are influenced by high nitrate content

The anaerobic ammonium oxidizing(anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However,the diversity and abundance of anammox bacteria in nitrogen(N)-rich agricultural soils under high fertilizer greenhouse conditions are still unclear. Two greenhouse fields with different N fertilizer input levels were chosen, and their soil profiles were studied with molecular technologies, including quantitative polymerase chain reaction assay, a clone library, and phylogenetic analysis based on hzsB(encoding anammox hydrazine synthase β-subunit) gene. Molecular analyses suggested that anammox bacteria were at their highest density at 10–20 cm soil depth, and that the anammox bacterial abundance was significantly lower at high N than at low N. Candidatus Brocadia was the sole anammox bacterial genus throughout the soil depth profiles. The highest diversity of anammox bacteria was found at 30–40 cm soil depth, and different phylotypic clusters of Candidatus Brocadia were associated with specific soil environmental factors, such as nitrates, soil depth, and total N. Correlation analyses and redundancy analyses confirmed that high nitrate content associated with high N fertilizer input had a significant negative influence on the abundance and biodiversity of anammox bacteria. These results imply that excessive use of N fertilizer would affect arid land soil N loss to the atmosphere by the anammox pathway.