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Poor soil has restricted the crop production in semiarid soil. Fulvic acid (FA) is considered to play an significant role in soil fertility. The amount and structure of FA after application of different organic wastes (OWs) was assessed in this work. Six treatments were involved in this experiment: chemical fertilizer combined with chicken manure (CM), sheep manure (SM), maize straw (MS), fodder grass (FG), and tree leaves (TL), while chemical fertilizer only was used as control (CK). The soil FA content (P < 0.05) after the application of TL was the highest than other OWs. The E 4 /E 6 ratios, Δlog K values, aliphatic C/aromatic C ratios of soil FA after the application of TL were the lowest than other OWs, whereas the C/H ratio was the highest. The specific fluorescence intensities (SFI) of peak A (Ex/Em 260–265/415-430 nm) and peak B (Ex/Em 310–315/415-430 nm) from EEM fluorescence spectrum of FA were the lowest after the application of TL. In conclusion, the application of TL was the most effective for improving FA accumulation, and making FA complex and stability. Thus, TL is the recommended OW for use in semiarid soil under plastic mulched drip irrigation conditions. The soil FA content after application of TL was the highest. • The application of TL could make the structure of FA complex and stability, and improve storage of soil organic matter. • The application of CM could make the structure of FA simple and improve the updating of FA. • TL would be used as the most suitable OW type in semiarid soil under plastic mulched drip irrigation conditions. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the variation in the amount and structure of humic acid (HA) after the application of organic wastes (OWs) in semiarid soil under plastic mulched drip irrigation, measured by elemental composition, excitation-emission matrix (EEM) fluorescence, and carbon 13 nuclear magnetic resonance ( 13 C CPMAS NMR). The experiment involved chemical fertilizer combined with chicken manure (CM), sheep manure (SM), maize straw (MS), fodder grass (FG), and tree leaves (TL), while chemical fertilizer only was used as control (CK). The highest cation exchange capacity (CEC), soil organic carbon (SOC), and HA contents ( P < 0.05) were achieved for TL compared to other OWs. The E 4 /E 6 ratio, Δlog K value, and the aliphatic C/aromatic C ratio of HA were the lowest for TL treatment than for other OW treatments, whereas the highest C/H ratio was obtained. The specific fluorescence intensities (SFI) of peak A (330–370/460-490 nm), peak B (450–465/515-525 nm), and peak C (255–270/465-490 nm) mainly referred to humic acid component from EEM fluorescence spectrum of HA were lower for TL compared to other OWs. In conclusion, the application of TL was the most effective for improving the accumulation of SOC and HA, and making the structure of HA complex and stability. Thus, TL is the recommended OW for use in semiarid soil under plastic mulched drip irrigation conditions. [ABSTRACT FROM AUTHOR]

The potential for sustaining grape production and improving crop water productivity in semi-arid areas through direct root-zone irrigation (DRZ) has been demonstrated in recent studies; however, it has only been tested for red wine grapes in sandy soils. To expand its application, a field study was conducted to investigate the influences of DRZ with reduced irrigation rate on yield, berry quality, root growth, plant water status and crop water productivity of white wine grape Vitis vinifera L. cv. Chardonnay grown in a silt loam soil within a semi-arid region of Washington state, USA. Compared with the surface drip irrigation which has been applied for decades in the study area, DRZ could improve the crop water productivity by 23 – 34 % and reduce the irrigation amount by 16 – 23 % without yield loss under variable weather conditions, indicating the efficacy of the DRZ as a novel subsurface irrigation strategy. Concurrently, DRZ restricted root distribution within 0 – 60 cm soil layers, and significantly reduced root number and root length density were observed in 20 – 40 cm soil depth. Moreover, grapevines under moderate water stress induced by DRZ accumulated more soluble sugar (8.8 % increase in °Brix on average) and yeast assimilable nitrogen (24.4 % increase on average) in berries. We conclude that proper deficit irrigation applied through DRZ would be applicable to optimize the water use for production and efficiently alter the root distribution pattern of Chardonnay grapevine cultivated in moderately permeable soils with improved berry quality. • Direct root-zone irrigation (DRZ) was compared with surface drip irrigation in Chardonnay vineyards. • DRZ strategy enhanced crop water productivity with minor effects on yield. • DRZ significantly restricted root growth in the 20–40 cm soil layer. • Total soluble solids and yeast assimilable nitrogen in berries were increased under DRZ. [ABSTRACT FROM AUTHOR]

Plant parasitic nematodes are the most devastating pest in continuous soybean monoculture, which have been managed mainly by chemical nematicides. However, safe and alternative methods need to be developed. A variety of organic materials are used for this purpose, but the control efficiency of different organic materials for nematodes has not been assessed in a comparative manner. Therefore, based on a 7-year experiment of continuous soybean monoculture, we directly compared the effects of different organic materials (maize straw combined with chemical fertilizer (F + S), poplar leaf combined with chemical fertilizer (F + L), cow manure combined with chemical fertilizer (F + C) and only fertilizer as CK) on nematode trophic groups and functional guilds under the same condition. Despite the lack of total nematode density differences, organic materials altered the soil nematode community in a soybean monoculture system. The relative abundance of plant parasites was highest in F + L treatment, followed by F + S treatment, while lowest in F + C and CK treatments. Meanwhile, bacterivores and fungivores had a higher relative abundance in CK and F + C treatments and a lower relative abundance in F + L and F + S treatments. Furthermore, significant treatment effects were also observed on the relative abundance of different functional guilds, except colonizer-persister (c-p) 5 plant parasites. The relative abundance of c-p 2 bacterivores was significantly higher in CK and F + C treatments than in F + S and F + L treatments, while the relative abundance of c-p 3 omnivore-carnivores was significantly higher in F + S and F + L treatments than in CK and F + C treatments. Organic materials treatments had a significant effect on Shannon index (H’), plant parasite index (PPI), structure index (SI) and enrichment index (EI) ( P  < .05), and the significant effects varied among different organic materials treatments. The results of this study suggest that the influence on the soil nematode community of organic materials is associated with their chemical composition, and so is its efficacy of controlling plant parasitic nematodes. [ABSTRACT FROM AUTHOR]