中国生态农业学报(中英文)

Phosphorus flow from large-scale fertilizer and feed additive chemical enterprises

CHEN Xuanji, CHEN Xiaohui, BAI Zhaohai, MA Lin

2017, 25(11): 1565-1579. doi: 10.13930/j.cnki.cjea.170299

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Abstract:
Phosphorus (P), as an essential nutrient for crops and livestock, is a non-renewable resource. In order to improve the productivity of agriculture and animal husbandry, about 80% of phosphate rocks are used to produce phosphate fertilizers and P feed additives. Therefore, it is very important to improve the production efficiency of P. However, information on flow characteristics and use efficiency of P in the production chain of "mining-benefaction-phosphoric acid-P fertilizers (feed additive)" has remained scarce. This study was done in support of establishing database on P flow through enterprise survey. The fertilizer and feed additive production module of NUFER (NUtrient flows in Food chains, Environment and Resources use) model, which is based on Material Flow Analysis (MFA) was used. Using a large P chemical enterprise in China as a case study, we analyzed P flow characteristics, P use efficiency, P footprint and P loss in the "mining-benefaction-phosphoric acid-P fertilizers (feed additive)" system and future scenarios for P chemical enterprises. The results showed that of the 3 902 Gg P ore resources (100% P₂O₅, the same as below), only 2 426 Gg ended up in fertilizers and P feed additives in 2015. Diammonium phosphate (DAP) was the highest yield product (1 558 Gg), followed by mono-ammonium phosphate (MAP), NPK compound fertilizer (NPK), triple superphosphate (TSP), di-calcium phosphate (MDCP) feed additive, single superphosphate (SSP), NPS compound fertilizer (NPS) and potassium dihydrogen phosphate (KH₂PO₅). The corresponding yields were respectively 634 Gg, 154 Gg, 130 Gg, 34 Gg, 22 Gg, 3 Gg and 1 Gg. The production efficiency was 99% for NPK, 98% for DAP, MAP and NPS, 95% for MDCP, 93% for TSP and 91% for SSP and KH₂PO₅. The production efficiency of the entire production chain was 80%. Most of the P loss came from phosphate rock processing, which accounted for 51% of total P loss. This was followed by mining (25%) and phosphoric acid product (14%). By optimizing production efficiency and improving recycling rate of wastes, P loss was expected to reduce by 42%. Although the utilization efficiency of P in the enterprise was at an advanced stage in China, there was still room for improvement.

Carbon storage of soil-vegetation system under different land use patterns in saline coastal regions

LI Xiaoguang, GUO Kai, FENG Xiaohui, LIU Xiaojing

2017, 25(11): 1580-1590. doi: 10.13930/j.cnki.cjea.170263

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Abstract:
Research on the coupling relationship between land use change and carbon sequestration potential in soil-vegetation systems in saline coastal plains has been of great theoretical and practical significance in terms of optimizing the implementation of land use with the purpose of vegetation restoration and enhancing carbon sink. This study used an abandoned bare saline-alkali land as the control to determine the dynamic changes in carbon storage in soil-vegetation systems under 3 years and 10 years old Tamarix chinensis plantations, 2 years and 8 years old Lycium chinense plantations, and frozen saline water irrigated cotton field with plastic mulching, and cotton field only mulched with plastic film. Based on continuous observation and quantitative description, we discussed carbon sequestration potential of soil-vegetation systems under the land use patterns and provided theoretical basis for increased regional carbon storage. The results were as follows:1) T. chinensis and L. chinense plantations and cotton cultivation with frozen saline water irrigation and plastic mulching significantly increased soil organic carbon content and reduced soil bulk density. T. chinensis planted for 10 years and L. chinense planted for 8 years had the highest carbon storage, 118.24 t·hm^-2 and 96.27 t·hm^-2, which recorded carbon storage increases of 58.51 t·hm^-2 and 36.54 t·hm^-2 respectively over cotton fields under frozen saline water irrigation with plastic mulching treatment. It also increased by 83.39 t·hm^-2 and 61.42 t·hm^-2 respectively over abandoned bare saline-alkali lands. 2) T. chinensis planted for 3 years and L. chinense planted for 2 years had the highest carbon sequestration rate, which was respectively 10.08 t·hm^-2·a^-1 and 2.71 t·hm^-2·a^-1. The rate of carbon sequestration was lowest (0.53 t·hm^-2·a^-1) for cotton field under frozen saline water irrigation with plastic mulching. T. chinensis planted for 10 years and L. chinense planted for 8 years had the weakest performance as carbon source and needed increased carbon storage by land use change or vegetation regeneration. The carbon storage of cotton field only with plastic film mulching decreased 0.86 t·hm^-2 per year due to remove of cotton straw. The abandoned bare saline-alkali land was a carbon source because not exogenous carbon input, whose carbon storage decreased 1.42 t·hm^-2 per year. By comparing the advantages and disadvantage of each land use type, T. chinensis and L. chinense cultivation was the most efficient way of increasing regional carbon storage in saline coastal regions.

Effect of rice-crayfish co-culture on greenhouse gases emission in straw-puddled paddy fields

XU Xiangyu, ZHANG Minmin, PENG Chenglin, SI Guohan, ZHOU Jianxiong, XIE Yuanyuan, YUAN Jiafu

2017, 25(11): 1591-1603. doi: 10.13930/j.cnki.cjea.170280

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Abstract:
Traditional agricultural systems are currently faced with the challenge of insufficient food production and reducing the negative effects of crop cultivation and population growth on the environment. One effective way to meet this challenge is the crop and animal co-culture in the paddy fields in South China. Rice-crayfish co-culture is the main component of such way, which has distinctive characteristics of deep waterlogging in off-rice season, total or partial direct straw return to fields, crayfish breeding in the whole year and strong crayfish burrowing, rapid planting area and high economic benefits. While the burrowing behavior of crayfish increases water-soil surface area, deep water management increases total dissolves oxygen and concurrently weakened methane transmission via bubbling. Although all the above measures theoretically reduce methane emission in paddy fields, the potential effect on global warming of rice-crayfish co-culture systems is not entirely clear. This study involved three treatments-waterlogging in off-rice season (W), waterlogging in off-rice season with straw return (WS) and waterlogging in off-rice season with straw return and crayfish (WSC). The aim was to investigate the characteristics of methane (CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions under different treatments and to provide data support for accurate assessment of paddy greenhouse gas emission. The results showed that the cumulative CH₄ emissions were respectively (10.0±1.2) g·m^-2, (9.2±2.8) g·m^-2 and (12.7±1.2) g·m^-2 under W, WSC and WS in 2015 and (28.5±5.2) g·m^-2, (26.8±2.1) g·m^-2 and (45.6±3.3) g·m^-2 under W, WSC and WS in 2016. Compare with W, cumulative CH₄ emission under WS increased by 27.23% and 60.08% respectively in 2015 and 2016. Compared with WS, WSC decreased cumulative CH₄ emission respectively by 29.02% and 41.19% in 2015 and 2016. Cumulative CO₂ emission significantly increased under WS, compare with W in both years. There was only a slight effect on cumulative N₂O emission of WS and WSC compared with W. Rice yield was 8.81 t·hm^-2 under WSC treatment and not different between W and WS treatments. Global warming potential (GWP) of WS significantly increased compare with W, and this increase was suppressed by WSC due to decreasing CH₄ emission. Then compared with WS, WSC treatment significantly decreased greenhouse gas intensity. There were no significant differences in soil dissolved organic carbon, acetic acid, NH₄⁺-N and NO₃^--N contents among W, WS and WSC. Compare with W and WS, WSC considerably increased rice-crayfish co-culture benefits per unit area with less greenhouse gases emission.

Effect of conservation tillage on soil fertility under rice-rape rotation system

YIN Zhiyao, HUANG Li, XUE Bin, HUANG Yanan, LI Xiaokun, LU Jianwei

2017, 25(11): 1604-1614. doi: 10.13930/j.cnki.cjea.170433

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Abstract:
In this study, the long-term effects of straw returning and no-tillage on physical properties and nutrient content of soils were assessed by continuous monitoring of soil bulk density, porosity, pH, organic matter, total nitrogen, total potassium, available nitrogen, available phosphorus and available potassium. The study considered different soil layers (0-20 cm and 20-40 cm) under rice-rape rotation system in Wuxue, Jingzhou and Wuhan Cities in Hubei Province for various farming years (9, 5 and 3 years) and cultivation systems. Also the Nemoro index method was used to evaluate soil fertility in different soil layers. The aim of the study was to provide the scientific basis for application of conservation tillage measures and optimization of field management. Results showed that:1) straw returning reduced soil bulk density by 2.00%-16.54% and increased total porosity by 1.00%-15.07% in rice and rape seasons. The changes in rape season were reversed under no-tillage treatment, while no significant changes were noted in the rice season. 2) Straw returning treatment increased the contents of organic matter (4.76%-35.07%), total nitrogen (1.80%-32.03%), available phosphorus (20.95%-65.82%), available nitrogen (5.97%-37.00%) and available potassium (8.71%-133.04%) in the 0-20 cm soil layer across the three sites. Compared with other nutrients, the greatest increase was recorded in available potassium. No significant differences were observed in no-tillage, although it had the best effect in terms of increase in soil nutrients compared with the other treatments after straw returning. The effect of each treatment on the 20-40 cm soil layer was similar to that on the 0-20 cm soil layer, but the total effect in terms of increase in the investigated parameters was not significant. 3) The no-tillage + straw returning and the nitrogen, phosphorus, potassium fertilizers application + straw returning treatments led to more increase in soil fertility with higher increase in integrated fertility index (7.56%-25.93%), they were good choice for improvement of soil fertility in the study sites.

Effect of facility management regimes on soil bacterial diversity and community structure

DU Siyao, YU Miao, LIU Fanghua, XIAO Leilei, ZHANG Hongxia, TAO Jun, GU Wei, GU Jingyan, CHEN Xi

2017, 25(11): 1615-1625. doi: 10.13930/j.cnki.cjea.170291

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Abstract:
Organic agriculture is a sustainable alternative to conventional agriculture. However, little is known about the effect of both organic and conventional agriculture on the environment and on the soil microbial community. The hypothesis was that bacterial community structure is defined by different agronomic practices. The objective of this study was to show how cropping systems, organic and conventional facility management regimes affect bacterial community structure and diversity. The study was also intended to increase knowledge on the prediction of soil sustainability under specific agronomic practices. The Illumina platform Hiseq 2500 high-throughput sequencing technique was used to sequence facility soil bacteria 16S rRNA from 6 treatments (OS:organic management of Solanaceous vegetable continuous cropping; OL:organic management of leafy vegetable continuous cropping; OSL:organic management of leafy-Solanaceous vegetables rotation; CS:conventional management of Solanaceous vegetable continuous cropping; CL:conventional management of leafy vegetable continuous cropping; and CSL:conventional management leafy-Solanaceous vegetables rotation) in Shunyi District of Beijing in June 2016. A total of 17 278 operational taxonomic units (OTUs) and 318 851 effective sequences were detected in the sequence control condition. Compared with soil bacterial community composition, diversity, relative abundance and interaction between soil factors and bacteria in different treatments, the results showed great differences between organic and conventional soil samples in bacterial community composition, and with a higher diversity in organic management. Obvious differences were observed between crop rotation and continuous cropping for bacterial community composition under organic management, while there was no significant difference between crop rotation and continuous cropping for bacterial community composition under conventional management. Soil bacterial diversity for rotation treatments was higher under organic management. It was found that there were mainly 14 genera of bacterial community, including Sphingomonas (5.05%) and Bacillus (4.84%). The abundance of the 14 genera changed significantly between organic and conventional management. There were insecticides degrading bacteria (Sphingomonas, Pseudomonas and Agromyces), disease controlling bacteria (Blastococcus and Lysobacter) and nitrification promoting bacteria (Candidatus Entotheonella and Microvirga) in conventional system. There were plant growth promoting bacteria (Bacillus) and organism degrading bacteria (Arthrobacter, Bhargavaea, Bryobacter, Candidatus Solibacter, Acidothermus and Tumebacillus) in organic system. Redundancy analysis also showed that soil bacterial community was affected mainly by soil total phosphorus, available phosphorus, and soil organic matter. Organic matter-decomposing bacteria Tumebacillus, Candidatus Solibacter and Acidothermus were positive associated with soil organic matter content. Therefore, the difference between organic and conventional soil samples for bacterial community originated from different fertilizer use methods, insecticide use methods and management patterns. Crop rotation promoted soil nutrient cycle and disease control under organic management. The results suggested that ecological adaptation mechanisms of different functional micro-organisms had significant differences in facility vegetable soils under different facility management regimes. The study provided the basis for further studies on exploring and explaining the characteristics and adaptation mechanisms of micro-organisms in facility soils under different facility management regimes.

Effects of saline-alkali stress on structure and abundance of bacteria/fungi community in rhizosphere soil of grafted cucumber seedlings

BAI Jingzhi, ZHAO Yuan, WU Fengzhi

2017, 25(11): 1626-1635. doi: 10.13930/j.cnki.cjea.170302

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Abstract:
Two saline-alkali tolerant and two saline-alkali sensitive rootstocks were used to graft cucumber to determine the effect of saline-alkali stress on microbial community structures in rhizosphere soil of grafted cucumber seedlings. The aim of the study was to explore mechanisms of salt-alkali tolerance of grafted cucumber and promote cucumber cultivation, and further enhance improvement of saline lands. The two saline-alkali tolerant rootstocks were 'Huazhen108' (T1) and 'Shenlitiemuzhen' (T2), the two saline-alkali sensitive rootstocks were 'Huitailang' (S1) and 'Jingxinzhenliuhao' (S2), and then the own-root seedlings of cucumber were used as the control. The physical and chemical properties of soil were adjusted after 10 days of grafted cucumber seedling planting for salinity using 100 mmol·L^-1 mixed salts solution, and the pH adjusted to alkalinity at 9.0. The molar ratio of the mixed salt solution was NaHCO₃︰Na₂SO₄︰NaCl︰Na₂SO₃=4︰2︰2︰0.15. Soils of different treatments were sampled after 30, 40 and 50 days of seedlings planting. And PCR-DGGE technique was used to study microbial community structure and species abundance in rhizosphere soil under cucumber seedlings grafted on different rootstocks. The results indicated that band number in DGGE of saline-alkali tolerant rootstocks was significantly higher than that of saline-alkali sensitive rootstock S2 and own-root cucumber. At the same time, both Shannon-Wiener index and evenness index of rhizosphere soil bacteria of saline-alkali tolerant rootstock T1 were significantly higher than those of the two saline-alkali sensitive rootstocks and own-root cucumber. The number of copies of 16S rDNA gene of bacteria of saline-alkali tolerant rootstock T1 was significantly higher than that of saline-alkali tolerant rootstocks S2 and own-root cucumber after 50 days of growth. The number of copies of ITS gene of fungi of saline-alkali tolerant rootstock T2 was significantly higher than that of saline-alkali sensitive rootstocks and own-root cucumber after 40 days of growth. The number of copies of ITS gene of fungi of saline-alkali tolerant rootstocks was significantly higher than that of saline-alkali sensitive rootstocks, though there was no significant difference between the grafted and own-root cucumber seedlings after 50 days of growth. Cucumber seedlings grafted on different rootstocks had significant differences in both rhizosphere soil microbial community structure composition and species abundance under saline-alkali stress, which became greater with increasing stress time, and changed soil micro-environment. In saline land, saline-alkali tolerant rootstock changed soil environment, and consequently improved grafted cucumber saline-alkali tolerance.

Response of florets development and grain formation in different spike wheat cultivars to nitrogen application

ZHAO Li, YANG Jiaheng, LI Shengnan, ZHA Feina, YUAN Tong, DUAN Jianzhao, ZHU Yunji

2017, 25(11): 1636-1642. doi: 10.13930/j.cnki.cjea.170212

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Abstract:
Wheat provides 20% of the calorie and protein consumed by humans. Further improvement in wheat yield potential is needed to meet future food demand. As yield is related to the number of grains, an understanding of the generation of grain is critical for increasing yield. Nitrogen is an important nutrient affecting the growth and development of wheat. Wheat yield is calculated as the number of grains per square meter, which in turn is related to the number of fertile florets at anthesis. In this study, the dynamics of floret generation and degeneration were studied in contrasting conditions of 0 kg·hm^-2, 180 kg·hm^-2 and 360 kg·hm^-2 of nitrogen (N). The modern, well-adapted large-spike wheat cultivar 'Zhoumai 16' and multi-spike wheat cultivar 'Yumai 49' were used at the materials. The results indicated that the dynamic characteristics of floret development of two cultivars were similar under different nitrogen applications with increasing degree-days (GDD). The dynamics of floret differentiation conformed to quadratic curve model. Besides, both floret degeneration and infertility conformed to linear equation. Moreover, the correlations were all significant. The large spike-cultivar 'Zhoumai 16' developed more florets than multi-spike cultivar 'Yumai 49', especially under nitrogen level of 180 kg(N)·hm^-2. For increased nitrogen application, large spike cultivar wheat 'Zhoumai 16' had more floret differentiation and faster floret differentiation and degeneration rates, which helped increase kernel number. This clearly indicated that the number of florets was not the only factor that determined grain number, hence there was need to place more focus on cultivation regulation at later stages of floret development. However, multi-spike cultivar 'Yumai 49' had more floret differentiation and fertile spikelet under medium nitrogen level[180 kg(N)·hm^-2] than under low and high nitrogen levels. Although the total number of floret differentiation of multi-spike cultivar 'Yumai 49' was less than that of large-spike cultivar 'Zhoumai 16', the degeneration and infertility rates were rather low. Compared with multi-spike cultivar wheat, the 1000-kernel weight of large-spike cultivar was highest for three different nitrogen levels. Under the experimental condition, yield of two cultivars of wheat peaked under 180 kg(N)·hm^-2. It was concluded that 180 kg(N)·hm^-2 increased kernel number of different spike cultivars. However, yield of large-spike cultivar 'Zhoumai 16' improved by increased spike and grain number under high nitrogen rate.

Effect of different nutrient combinations on root growth and nutrient accumulation in sorghum

CUI Peipei, LIU Peng, LIU Jiaqi, WANG Jinsong, WU Ailian, DONG Erwei, DING Yuchuan, JIAO Xiaoyan

2017, 25(11): 1643-1652. doi: 10.13930/j.cnki.cjea.170300

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Abstract:
Sorghum, one of the important grains in the world, can grow well in low fertility soils. In order to understand the response of nutrient accumulation and root growth in sorghum to N, P and K stresses, a long-term experiment consisting of 5 treatments (NPK, PK, NK, NP and CK) under conditions of sorghum/maize rotation system was initiated in 2011. The indi-vidual treatments of the experiment ensured differences in availability of soil N, P and K before sowing sorghum in 2016. The results showed that compared with NPK treatment, PK treatment increased total root length by 18.29% and decreased total root volume by 26.53%. Also under PK treatment, sorghum root distribution was mainly in the 0-10 cm soil layer. The proportion of fine roots with diameter less than 0.5 mm increased significantly under PK treatment. Compared with NPK, total length, total surface area and total root volume of sorghum decreased respectively by 24.03%, 27.48% and 41.29% under NK treatment. Without K (i.e. under NP treatment), the growth of fine roots was inhibited. Removal of either N or P or K decreased the accumulation of the corresponding element in sorghum. It was recommended not to induce N or limit N and K translocation from vegetative organs to grains. Both the combinations NK and NP inhibited the transfers of N, P and K to grain from vegetative parts. The accumulation and translation of N, P and K were regulated by root morphology. There were significant relationships between both N and K accumulation and individual root parameter (total root length, total root surface area and total root volume). Compared with P and K accumulation, N accumulation in sorghum had an obviously correlation with both N translocation from vegetative organs to grains and aboveground biomass. In summary, the response of root morphology and nutrient accumulation in sorghum to individual N, P or K stress was different. The results were useful for the cultivation of sorghum in marginal soils.

Effects of reducing potassium fertilizer on rice yield and potassium use efficiency under wheat straw return condition

JIN Mengcan, ZHANG Shuyu, GAO Hongjian, GAO Shifeng, WANG Yikun

2017, 25(11): 1653-1660. doi: 10.13930/j.cnki.cjea.170137

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Abstract:
There has been an increasing soil potassium deficiency in China. However, crop residues generally contain high level of potassium that could replace part of the potassium fertilizer requirements after returning straw to the soil, and can therefore alleviate soil potassium deficiency. Crop residue return to field is an effective way to reduce the use of potash fertilizer, which also improves potassium use efficiency. In this study, field experiments were carried out to determine rice yield potassium accumulation and partial factor productivity of potash fertilizer under conventional potash fertilizer application of 135 kg(K₂O)·hm^-2 (control) and reductions by 10%, 20%, 30% and 40% after wheat straw incorporation (6 000 kg·hm^-2). The potassium content and the quantity of accumulated potassium in rice reduced with decreasing potassium fertilizer application after straw incorporation into the soil. The yield, economic benefit, effective panicle number, grains per panicle and seed-setting rate of rice declined with the reduction of conventional potassium fertilizer rate from 10% to 40%. However, when potassium fertilizer was reduced by less than 30%, there was little impact on 1000-grain weight of rice. It also had no significant effect on yield or economic benefit of rice (P>0.05). Compared with conventional fertilization, treatments with chemical potash fertilizer reduction of 10%, 20%, 30% and 40% increased partial factor productivity of potassium fertilizer by 8.4%, 18.9%, 33.8% and 44.4%, respectively. In summary, potassium accumulation in rice plant, rice yield and economic benefit decreased, whereas partial productivity of potassium increased with the reduction of conventional potassium dose from 10% to 40%. When wheat straw was applied and conventional potassium fertilization dose reduced by less than 30%, partial factor productivity of potassium fertilizer increased but had no significant effect on the yield and economic benefit of rice.

Effect of cropping pattern on agronomic characteristics, yield and quality of radix isatidis

WANG Enjun, CHEN Yuan, HAN Duohong, CAI Ziping, ZHANG Fenqin

2017, 25(11): 1661-1670. doi: 10.13930/j.cnki.cjea.170198

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Radix isatidis (Isatis indigotica Fort.), a biennial cruciferous plant, is an important traditional Chinese medicine plant that is extensively cultivated across China. Its main producing area is in the central region of Hexi Corridor in Qilian Mountaint. In 2012, Minle County in Ganshu Province was named the "hometown" of radix isatidis in China. However, standardized cultivation technique has been the main problem affecting the yield and quality of radix isatidis. Cropping pattern has been critical for yield and quality of Chinese medicinal plants. In order to explore the best cropping pattern for radix isatidis in irrigated oasis in Hexi Corridor, we designed a two-factor randomized block field experiment. One factor was the cultivation model (consisting of ridge plowing and flat breaking) and the other was film mulching (no film cover, white film cover and black film cover). The experiment included six cropping patterns-flat breaking without film mulching, flat breaking with white film mulching, flat breaking with black film mulching, ridge plow without film mulching, ridge plow with white film mulching, and ridge plow with black film mulching. The agronomic characteristics of root, yield and content of epigoitrin in radix isatidis under different treatments were determined every month for period from sowing to harvest. Results showed that under different cultivation methods, main root length, root diameter and root dry weight of individual plant tracked S-shaped curve across the growth stages that was best fitted by logarithmic growth equation. The differences in root yield under various cultivation methods were significant. While ridge plow with black film mulching had the highest yield (4 514.45 kg·hm^-2), ridge plow with white film mulching had the lowest yield (3 116.378 kg·hm^-2). Different treatments had significantly effects on epigoitrin content in radix isatidis. While ridge plow with white film mulching had the highest epigoitrin content (2.61 g·kg^-1), ridge plow without film mulching had the lowest epigoitrin content (1.37 g·kg^-1). Ridge plow with black film mulching cultivation method should be widely used in radix isatidis cultivation in the irrigated oasis in Hexi Corridor.

Effect of moistube-irrigation on crop yield and water use efficiency

ZHANG Mingzhi, NIU Wenquan, LU Zhenguang, LI Yuan, WANG Jingwei, QIU Xinqiang

2017, 25(11): 1671-1683. doi: 10.13930/j.cnki.cjea.170243

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In this study, summer corn and winter wheat were used to explore the effect of moistube-irrigation on crop growth and yield to support the generalization and application of moistube-irrigation technology. Comparative experiment was set up in a completely randomized design in order to determine yield, water use efficiency of summer corn and winter wheat and soil electrical con-ductivity. The treatments of the experiment included moistube-irrigation with different distances between moistubes (60 cm, 40 cm and 20 cm) and subsurface drip irrigation and no irrigation as the controls. The irrigation amount of moistube-irrigation was 1/4-4/5 that of subsurface drip irrigation. The results showed crop yield decreases under moistube-irrigation treatments due to lower irrigation amount. However, the decrease was not significant for winter wheat though it was significant for summer corn. Water use efficiencies of both crops were not significantly changed under moistube-irrigation treatments compared with the treatment of subsurface dir irrigation, while the irrigation water use efficiencies of crops were increased significantly. While crop yield increased with decreasing moistube interval, crop water use efficiency and irrigation water use efficiency decreased. For the Lou soil region which contains less water, the best moistube layout distance in the region was 60 cm according to the results of crops yields and water use efficiencies. This improved irrigation water use efficiency without significantly reducing yield. In addition, moistube distance had little effect on soil electrical conductivity. With increasing soil depth, there was no significant difference (P>0.05) in soil electrical conductivity in each growth period of two crops. Also it's variation trends in moistube-irrigation and subsurface drip irrigation were very similar. It suggested that the effect of moistube-irrigation and subsurface drip irrigation on soil electrical conductivity was consistent. Therefore, moistube-irrigation was much as applicable in summer maize and winter wheat cultivation as subsurface drip irrigation. The correlation between crop yield and soil electrical conductivity at the 10-20 cm soil layer and average soil electrical conductivity at the 10-80 cm soil layer was significant under moistube-irrigation. Hence, it was feasible to estimate crop yield by using soil electrical conductivity at the 10-20 cm soil layer and average soil electrical conductivity at the 10-80 cm soil layer. The above research provided the basis for the application of moistube-irrigation technology in summer corn and winter wheat cultivation.

Reproductive and stress resistance characteristics of wild oat and its allelopathic effects on common wheat

ZHAO Wei, WANG Yanjie, LI Lin, WANG Xin

2017, 25(11): 1684-1692. doi: 10.13930/j.cnki.cjea.170224

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As a widespread malignant weed in farmlands, wild oat has strong survival ability and can adopt multiple strategies to cope with various and changing environmental stresses. This high adaptive ability always makes wild oat to occupy a dominant place in the interspecific competition. In this study, the reproductive and dispersal characteristics of the population, stress resistance of seeds and seedlings, and allelopathic effects (root exudates) on common wheat seedlings of wild oat were investigated. The study aimed to understand the survival strategies of wild oat and find effective methods of controlling natural spread of this plant species. The main results of the study were as follows:1) Wild oat had a strong sexual reproduction and population dispersal ability in farmland ecosystems. This included earlier flowering and higher grain-setting than common wheat, high seed yield, huge seed bank, far seed dispersal distance, etc. 2) The germination of wild oat seed occurred within a wide temperature range and could germinate normally under room or varying temperature conditions. Room temperature was the optimum condition for wild oat seed germination after freezing treatment, which was highly benefited the plant by breaking seed dormancy and increasing total germination rate to up to 93.33%. 3) Wild oat seed had some adaptable responses to the salt stress, but germinated normally when NaCl concentration was below 1.80%. 4) Wild oat seedling was also adapted very well to both salt and drought stresses. Proline accumulation in seedling leaf of wild oat increased significantly (P < 0.01) with gradual increase in NaCl or PEG concentration. However, catalase activity of wild oat seedling leaf increased at the start of NaCl or PEG stress and then declined as NaCl or PEG concentration increased. 5) Root aqueous extract of wild oat negatively affected the plant height, plant dry weight, root length and root vitality of wheat, which was significant at P < 0.01 level. This demonstrated that the root of wild oat had a strong allelopathic effect on the growth of common wheat seedling. The above results suggested that the competitive advantage of wild oat was reflected in several ways-strong sexual reproduction and seed dispersal ability, high resistance to salt and drought adversities, and significant allelopathic effect on adjacent plants. Related in depth studies were required to provide firm theoretical basis for controlling wild oat dispersal in farmlands, especially in wheat fields.

Characteristics and driving factors of land use change in the Bojiang Lake Basin in Ordos Plateau, China

YAN Guozhen, ZHANG Zheng, LIANG Kang, LOU Huajun

2017, 25(11): 1693-1706. doi: 10.13930/j.cnki.cjea.170012

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Abstract:
Land use change can directly affect the variety and intensity of terrestrial ecosystem service functions. The Bojiang Lake Basin (BLB) is located in the Ordos Plateau in China and it belongs to the fragile ecosystem of the arid/semi-arid region.In the last decade, degradation of ecosystem services function in BLB has further jeopardized the endangered Larus relictus birds. Land use structure and pattern in BLB have changed significantly in recent decades. However, few studies have been done on land use change and the related driving factors. This study aimed to investigate the characteristics and the related driving factors of land use change in BLB during 1990-2015 to provide a reference base for the improvement of ecosystem services function and the protection of L. relictus birds. In the study, six periods (1990, 1995, 2000, 2005, 2010 and 2015) of 30 m resolution of land use data were extracted from Landsat remote sensing images. Land use change was investigated using trend and status index methods and then the main driving factors (i.e., climate change and human activity) analyzed. The results showed that grassland, farmland and unused land were the main land use types in 1990-2015, and there was significant change in land use in the BLB study area. Based on spatial variation, there was an increasing trend in farmland in the eastern, western and north-central regions, and then a decreasing trend in unused land in the southern region. The characteristics of the variation in area and dynamic conversion of each land use type were different. There was a dynamic balance in transformation in high, medium and low coverage grasslands, occupying some 70% of the lake basin. Farmland and unused land respectively had an apparent increase and decrease in trend. There was 6.05% increase in farmland area and 7.62% decrease in unused land area in the lake basin. Grassland was the main source of income for farmlands and therefore the main export for unused lands. The water area was decreased by 1.45% of the total area in 1990-2015, with bottomland as the main export. In the period 1995-2000 there was frequently transformation in land use, which in 2005-2010 had the most dynamic imbalance in land use change. Both climatic factors and human activities significantly affected land use change in the BLB study area. Specifically in 1990-2015, the transformation in land use types was due to the combined effects of warming and drying climate (expressed as declining precipitation and rising temperature) and intensifying anthropogenic disturbances (expressed as ecological restoration and water conservancy projects). The increase in farmland, woodland and buildup area and the decrease in unused land were more affected by anthropogenic disturbances. The decrease in water body and high coverage grassland and the increase in medium and low coverage grasslands were due to both climatic factors and human activities. Therefore, a reasonable land use planning such as restricting planting of forest with high water use, reducing the area of farmland in the catchment of the upper reaches of the rivers was critical for the protection for healthy and sustainable development of the study area.

Characteristics of surface albedo in subtropical paddy rice fields

BAI Xinxin, HUANG Xiaolin, QIN Mengsheng, ZHANG Yuefang, CHEN Liugen, GUO Zhi, HAO Lu

2017, 25(11): 1707-1717. doi: 10.13930/j.cnki.cjea.170276

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Abstract:
As a key input parameter of numerical climate models and surface energy balance equations, surface albedo affects climatic systems on the earth. Data observed on rice paddy surface albedo not only better depict energy distribution between ground and atmosphere in paddy fields, but also provide more accurate parameters values for land surface models. It also provides authentication for remote sensing inversions of surface albedo and therefore better explains the effects of land use/cover change mechanism on global climate change. Using CNR4 measured surface albedo in paddy fields at Lishui Experiment Station in 2016, we analyzed the characteristics of surface albedo of paddy field. In the study, we combined the analysis of surface albedo with temperature, humidity, wind speed, wind direction and other meteorological data. Some other possible factors affecting surface albedo in paddy fields were also analyzed. The correlation coefficient between surface albedo and temperature reflected the effect of land surface albedo on temperature. The correlation between surface albedo and meteorological factors (e.g., humidity and solar radiation) was used to study the relationship among surface albedo, temperature and humidity. The results showed that surface albedo had a U-type of distribution for sunny days, which was lowest at noon, highest in the afternoon and morning, but also affected by precipitation. Surface albedo on sunny days was asymmetrical, which was mainly caused by dew, wind speed and wind direction. As actual air temperature was close to dew point temperature at night, more dew settled on leaves in the morning. When solar altitude angle was small, the scattering effect of dew resulted in higher surface albedo in the morning than in the afternoon. When solar altitude angle was high, dew on leaf surfaces gradually evaporated. Southwest winds influenced the tilting of crop leaves, resulting in higher surface albedo in the afternoon than in the morning. Surface albedo was higher on sunny days than on cloudy and rainy days. The correlation coefficient between surface albedo and outgoing shortwave radiation was highest (0.670, P < 0.01) on sunny days, while the correlation coefficient between surface albedo and relative humidity was highest (-0.480, P < 0.05) on cloudy days. The trend in surface albedo during the growing season initially increased and then decreased. Surface albedo was highest during grain-filling to mature stage of rice and was lowest during transplanting to tillering stage. The correlation coefficient among surface albedo, humidity and shortwave radiation for rice growing season was high. Also the correlation coefficients between surface albedo and temperature, and then between humidity and shortwave radiation were not the same for different growth stages. During grain-filling period, the correlation among surface albedo, solar shortwave radiation and humidity was more significant, all at P < 0.01 significance level. Surface albedo changed greatly at tillering and jointing stages, and were significantly affected by climatic factors.

Spatiotemporal analysis of dew days in China's Loess Plateau

GAO Zhiyong, WANG Youke, JIANG Peng

2017, 25(11): 1718-1730. doi: 10.13930/j.cnki.cjea.170435

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Abstract:
Global warming due to greenhouse effect has altered meteorological variables such as temperature, relative humidity, rainfall and sunshine hours. The resulting change of these variables could have strong effects that threaten population, agriculture, environment, economy and industry. It could even affect global food security and supply/demand of water resources in the world. The Loess Plateau in North China is a semiarid and sub-humid climate region and is well-known for severe soil erosion, fragile ecological environment and sensitivity to climate change. Climate change will have a major impact on the ecological environment and agricultural ecosystems. Given the above, temporal and spatial distribution of meteorological elements for the Loess Plateau region has been analyzed. However, there was little information on dew days on the plateau. Dew Dew day was a key parameter of hydrologic cycle and plant disease prevention. Analysis of the spatial distribution and long-term temporal trends of dew days and the relatedness with climatic variables may provide the basis for plant disease prediction and prevention in local areas. In this study, dew day data from 52 meteorological stations for the period 1961-2010 were calculated using a model. The spatial distribution of seasonal and monthly dew days was interpolated by Kriging and the temporal trends of the days examined using trend-free pre-whitening (TFPW) and Sen's slope estimator. Correlation analysis explained the dew-day formation. The results showed that at monthly scale, dew days started in March and ended in November, with a monthly mean of 7 dew days. The maximum dew days were in the south, southeast and northwest of the Loess Plateau in September, with a range of 8-12 days. Analysis of dew days indicated significant positive trends for 5.77%-25.00% of the stations, with a variation of 0.02-0.15 d·a^-1 during the periods from August through November and June. Dew days with significant negative trends were found too, with the decrease in July and April by 0.02-0.09 d·a^-1 and for 7.68%-17.31% of the stations. At seasonal scale, dew days occurred in spring, summer and autumn, with a seasonal mean of 15 dew days. The maximum dew days were in autumn, with 14-26 dew days in the south, southeast and northwest of the plateau. Dew days with significant positive trends were observed in summer and autumn, which varied respectively by 0.09-0.25 d·a^-1 and 0.09-0.15 d·a^-1 for 3.85% and 5.77% of the stations. Dew days with significant negative trends were evident in spring, which varied by -0.34 to -0.07 d·a^-1 for 5.77% of the stations. Relative humidity and temperature had clear and dominant effects on the spatiotemporal trend of dew days. The study provided a quantitative basis for understanding dew day distribution and trend in the Loess Plateau under global climate change. It also provided a vital reference for future plant disease forecast, prevention and risk assessment.

2017 Vol. 25, No. 11