Excessive manure application stimulates nitrogen cycling but only weakly promotes crop yields in an acidic Ultisol:Results from a 20-year field experiment

Population growth and growing demand for livestock products produce large amounts of manure,which can be harnessed to maintain soil sustainability and crop productivity.However,the impacts of excessive manure application on crop yields,nitrogen(N)-cycling processes and microorganisms remain unknown.Here,we explored the effects of 20-year of excessive rates(18 and 27 Mg ha^(–1)yr^(–1))of pig manure application on peanut crop yields,soil nutrient contents,N-cycling processes and the abundance of N-cycling microorganisms in an acidic Ultisol in summer and winter,compared with none and a regular rate(9 Mg ha^(–1)yr^(–1))of pig manure application.Long-term excessive pig manure application,especially at the high-rate,significantly increased soil nutrient contents,the abundance of N-cycling functional genes,potential nitrification and denitrification activity,while it had a weaker effect on peanut yield and plant biomass.Compared with manure application,seasonality had a much weaker effect on N-cycling gene abundance.Random forest analysis showed that available phosphorus(AP)content was the primary predictor for N-cycling gene abundance,with significant and positive associations with all tested N-cycling genes.Our study clearly illustrated that excessive manure application would increase N-cycling gene abundance and potential N loss with relatively weak promotion of crop yields,providing significant implications for sustainable agriculture in the acidic Ultisols.

A high-resolution climatic change since Holocene inferred from multi-proxy of lake sediment in westerly area of China

Multi-proxy data are presented and a discuss is made of paleoclimatic and paleoenvironmental changes during Holocene from a 225-cm-long sediment core from Wulungu Lake, located in westerly area of China. The chronology is constructed from six AMS radiocarbon dates on the bulk organic matter. Analyses of pollen, TOC, TN, δ 13Corg, ostracod assemblages and the shell stable isotopes, suggest Holocene climate pattern as follows: temperate and dry (10.0―7.6 cal. ka BP)-warm and wet (7.6―5.3 cal. ka BP) -warm and moist (5.3―3.6 cal. ka BP) -temperate and dry (3.6―2.1 cal. ka BP)-temperate and moist (2.1―1.3 cal. ka BP) -cool and dry (1.3 cal. ka BP―present). With the climatic change, Wulungu Lake experienced two large-scale retreat (5.3―3.6 cal. ka BP and 1.3 cal. ka BP―present) and an obvious transgression (7.6―5.3 cal. ka BP). The records of climatic and environmental evolution of Wulungu Lake were in good accordance with those of adjacent areas. It responded to regional environmental change, global abrupt climate events and followed the westerly climate change mode.

Prevention and Control of Continuous Cropping Obstacle of Watermelon by Reductive Soil Disinfestation (RSD)

This study aimed to explore whether reductive soil disinfestation（RSD） is an effective method of controlling continuous cropping obstacle of watermelon. Samples of watermelon continuous cropping soils were treated by RSD in laboratory tests and pot experiments in August 2015 and from December 10,2016 to April 10,2017. The soil samples for the laboratory test were divided into 16 groups,and each group comprised three parallel samples of 100 g（dry soil weight）. Except for the original and control（CK） samples,the 14 other groups of soil samples were treated with different combinations of 1% or 3% alfalfa powder,1% or 3% ammonia（NH3） water,and 1% or 3% acetic acid. The soil samples were placed inside size-five self-styled plastic bags and incubated in a constant-temperature biochemical incubator at 35°C for 14 days after blending,flooding,and sealing. Seven groups of soil samples were designed for the pot experiments based on the laboratory test results. Each group consisted of 30 parallel samples of 3 kg（dry soil weight）. These samples were incubated outdoors for 4 months after mixing with alfalfa powder and/or NH3 and/or acetic acid according to the experimental design,blending,flooding,and sealing. Watermelon seedlings were planted in the air-dried soil samples from May to July in 2017. The results showed that the p H of the soil samples treated by RSD were elevated except for those samples with acetic acid. In addition,the electrical conductivities of the soil samples treated by RSD were effectively adjusted. The presence of soil-borne pathogenic Fusarium oxysporum f.sp. niveum was significantly suppressed（p 0.05） in soil samples treated by RSD,and the incidence and mortality rate of watermelons planted in these samples were remarkably lower than those planted in the CK and flooded CK soil samples. Therefore,continuous cropping obstacle of watermelon can be controlled by RSD.

Habitat suitability modeling based on remote sensing to realize time synchronization of species and environmental variables

Aims Remote sensing(RS)is a technical method for effectively capturing real-world data on a large scale.We aimed to(i)realize the time synchronization of species and environmental variables,and extract variables related to the actual growth of species based on RS in habitat suitability modeling,and(ii)provide a reference for species management.Methods Taking invasive species Ambrosia artemisiifolia in China as an example for habitat suitability modeling.Temperature and precipitation variables were calculated from the land surface temperature provided by the moderate-resolution imaging spectroradiometer(MODIS),and climate station data,respectively.Besides,other variables that directly affect the growth or reproduction of A.artemisiifolia were also included,such as the relative humidity of the previous year’s flowering period(RHPFP),and the effective UV irradiance reaching the Earth’s surface(UVI).The random forest method was selected to model the habitat suitability.The environmental variables and samples were divided into four-time periods(i.e.1990–2000,2001–2005,2006–2010 and 2011–2016)based on sampling time.Variables from the long-time series of RS(1990–2016)and WorldClim(1960–1990)were also modeled.Important Findings It was feasible to extract environmental variables from RS for habitat suitability modeling,and was more accurate than that based on the variables from WorldClim.The potential distribution of A.artemisiifolia in 1990–2000 and 2006–2010 was smaller than that in 2001–2005 and 2011–2016.The precipitation of driest months(bio14),precipitation coefficient of variation(bio15),RHPFP and UVI were the important environmental variables that affect the growth and reproduction of A.artemisiifolia.The results indicated that the time synchronization of species and environmental variables improved the prediction accuracy of A.artemisiifolia,which should be considered in habitat suitability modeling(especially for annual species).This study can provide an important reference for the management and prevention of the spread of A.artemisiifolia.