No-tillage Rice Research Articles

Lowland Integrated Crop–Livestock Systems with Grass Crops Increases Pore Connectivity and Permeability, Without Requiring Soil Tillage

Enhancing integrated crop–livestock systems (ICLSs) to improve land-use efficiency is a critical goal. Understanding the ICLS impacts on lowland soils is key to sustainable agricultural practices. Our objective was to test whether adopting ICLSs in lowlands improves soil structure, pore connectivity, and water and air permeability. This study was conducted in a long-term field trial, consisting of the following production systems with flood-irrigation rice: rice–fallow–rice, under conventional tillage and absence of grazing (RFR-ct); rice-grazed ryegrass–rice, under no-tillage and grazing (RGrR-nt); rice-grazed ryegrass–soybean-grazed ryegrass–rice, under no-tillage and grazing (RGrS/RGrR-nt); and a grazed pasture-consortium (winter) and succession field (summer), with no-till rice every 4 years (P4R-nt). Core samples were collected after grazing (October 2018), harvesting (March 2019), and grazing (October 2019). We analyzed soil air permeability, saturated hydraulic conductivity, pore connectivity by computed tomography. Soil tillage in a semi-direct system generated discontinuous porosity. Systems with intense trampling or less surface protection are affected by shearing on topsoil, reducing pore continuity. ICLSs are mainly composed of ryegrass–rice mitigated the harmful effects of trampling, and improved soil structure and functioning. Systems without soil tillage exhibited higher pore connectivity and pores with vertical orientation. Finally, soil tillage is not required to improve structural quality in ICLSs.

Season and No-Till Rice Crop Intensification Affect Soil Microbial Populations Involved in CH4 and N2O Emissions

Rice is an important source of methane (CH4) and other crops may be sources of nitrous oxide (N2O), both of which are powerful greenhouse gases. In Uruguay, irrigated rice rotates with perennial pastures and allows high productivity and low environmental impact. A long-term experiment with contrasting rice rotation intensification alternatives, including rice–soybean and continuous rice, was recently carried out in an Argialboll located in a temperate region of South America. To know if rotation systems influence soil microbial activity involved in CH4 and N2O emissions, the abundance and potential rate for gas production or consumption of microbial populations were measured during the rice crop season. CH4 was only emitted when rice was flooded and N2O emission was not detected. All rotational soils showed the highest rate for methanogenesis at tillering (30 days after rice emergence), while for methanotrophy, the maximum rate was reached at flowering. The abundance of related genes also followed a seasonal pattern with highest densities of mcrA genes being observed at rice flowering whereas pmoA genes were more abundant in dry soils after rice harvest, regardless of the rotation system. Differences were found mainly at tillering when soils with two consecutive summers under rice showed higher amounts of mcrA and pmoA gene copies. The potential denitrification rate was highest at the tillering stage, but the abundance of nirK and nirS genes was highest in winter. Regarding ammonium oxidation, bacterial amoA abundance was higher in winter while the archaeal amoA gene was similar throughout the year. A strong influence of the rice growth stage was registered for most of the parameters measured in rice paddy soils in this no-till rice intensification experiment. However, differences among rotations begin to be observed mainly at tillering when the abundance of populations of the methane and nitrous oxide cycles seemed to respond to the rice intensification.

Soil organic matter in physical fractions after intensification of irrigated rice-pasture rotation systems

Crop-pasture systems improve soil quality, but their intensification through the increase of the frequency of annual crops may reduce it. We evaluated the impacts of six no-till rice rotations systems on soil quality after five years in a field scale long term experiment established on a site with a 30 years old stabilized rice-pasture rotation. Rotations included: continuous rice (ContRc); rice-soybean (Rc-Sy); rice-soybean-rice-sorghum (Rc-Sy-Sg); rice-soybean-pasture (Rc-Sy-Past); and rice-pasture, with short (Rc-SPast) and long-term pastures (Rc-LPast). Cover crops were included in winter between cash crops. All rotation phases coexisted and were replicated three times in space. Soil quality indicators included: soil organic carbon and total nitrogen contents in bulk soil (TSOC and TN, respectively) and in particulate (>53 μm, POM-C and POM-N) and mineral associated soil organic matter fractions (<53 μm, MAOM-C and MAOM-N). Soil cores were collected at 0−5 cm and 5−15 cm soils depths (results presented at 0−5 and 0−15 cm depths). Additionally, soil samples were taken up to 60 cm soil depth every 15 cm for TSOC and TN. After five years, no differences were observed in TSOC (29.3 Mg C ha−1) or TN (3.16 Mg N ha−1) between rotations in the first 0−15 cm as well as for each layer and in the aggregated 0−60 cm of soil. Neither POM-C nor POM-N contents were different between treatments that had perennial pastures in the rotation. However, Rc-LPast had 18 and 19 % greater POM-C and POM-N respectively than the average of Rc-Sy and Rc-Sy-Sg, (6.06 Mg C ha−1 and 0.48 Mg N ha−1, 0−15 cm depth). Meanwhile, the POM-C represented 23.6 % of TSOC in Rc-LPast, but in rotations that replaced pastures (Rc-Sy and Rc-Sy-Sg) represented only 20 %. For soils in temperate zones, under a stable rice-pasture rotation, there are intensification alternatives which preserved TSOC in the midterm. However, the reduction in the particulate fractions observed in the rice rotations that substituted perennial pastures with other crops, suggests that TSOC may be more vulnerable to losses in the long term.

Advantages of nitrogen fertilizer deep placement in greenhouse gas emissions and net ecosystem economic benefits from no-tillage paddy fields

Unreasonable application of nitrogen (N) fertilizers gives rise to agricultural greenhouse gas (GHG) emissions, causing increases in carbon footprint (CF). To solve such problems, scholars have proposed the practice of N deep placement (DPN), which has been proven to be an effective approach to enhance N use efficiency and reduce N loss. However, the effect of DPN on CF and net ecosystem economic benefit (NEEB) from no-tillage (NT) rice fields remains largely unknown. In this work, a field experiment was conducted with a random complete block design to investigate the differences in soil CH4 and N2O emissions, agricultural GHG emissions, grain yield, CF, and NEEB from NT paddy fields between urea deep placement (UDP) and urea broadcasting (UBC) in central China. The CF for the entire rice production chain can be calculated as the ratio of total GHG emissions to grain yield using a life-cycle approach. The novelty of this study lies in the examination of the integrated effects of DPN on GHG emissions, grain yield, CF and NEEB from NT paddy fields. The agricultural GHG emissions varied from 1297.0 to 1420.8 kg CO2-eq ha−1. Chemical fertilizers dominated the GHG emissions. UDP resulted in 96.8 kg CO2-eq ha−1 more emissions than UBC due to more consumption of diesel by machinery operations. Compared with UBC, UDP significantly reduced soil CH4 emissions by 36–39% and N2O emissions by 29–31%. The mitigation of soil CH4 and N2O emissions under UDP decreased the total GHG emissions by 34% and CF by 46%. Soil CH4 emissions accounted for 83–88% of the total GHG emissions. The NEEB under UDP was 48% higher than that under UBC. In conclusion, DPN can increase grain yield, reduce CF, and enhance NEEB from NT rice fields, and may be an economic and cleaner approach for rice production.

Earthworm responses to cropping rotation with oilseed rape in no-tillage rice fields and the effects of earthworm casts on human-essential amino acid content in rice grains

The rice-oilseed rape rotation is a major rice-based cropping system in the Yangtze River basin in China, and no-tillage technology has been successfully adopted in this system. The main objectives of this study were to determine: (1) the response of earthworm density to rotation with oilseed rape in no-tillage rice fields; and (2) the effects of earthworm casts produced during the oilseed rape-growing season on the content of human-essential amino acids in resulting rice grains. An on-farm study was conducted from 2015 to 2017 to compare earthworm density in no-tillage fields where rice was rotated with oilseed rape and with a fallow period. A micro-plot experiment was also carried out to compare the grain content of human-essential amino acids in rice with and without the addition of earthworm casts (produced during the oilseed rape-growing season) under three nitrogen fertilizer rates. We observed that medians of earthworm number per m2 were 68–154% higher in the fields rotated with oilseed rape than in the fallow fields. The contents of human-essential amino acids detected in rice grains were generally increased by the addition of earthworm casts, and there were significant increases (8–13%) for phenylalanine, threonine and valine. Our study suggests that earthworms can be increased by rotation with oilseed rape in no-tillage rice fields, and that their casts can increase the contents of human-essential amino acids in rice grains.

Soaking seeds with paclobutrazol enhances winter survival and yield of rapeseed in a rice-rapeseed relay cropping system

Rice-rapeseed relay cropping is an effective way to use winter fallow fields and increaseland use efficiency. However, the overlapping period of 10–15 days for rice-rapeseedcultivation results in reduced winter survival and less yields. Therefore, in this study, weinvestigated if the treatment of oil rape seeds with paclobutrazol (PAC) improves its winterhardiness and yields by altering its crop morphology. First, a pot experiment was conducted todetermine the appropriate PAC concentration to soak seeds upon seedling growth and thegermination rate. Another pot trial was performed to check the responses of different rapeseedcultivars to the proposed treatment. Rapeseed was cultivated in no-tillage rice fields at anexperimental site in Wuhan from 2009 to 2011. In the absence of PAC treatment, rapeseed sownin pots and rice fields showed excessive elongation of the crown, which resulted in low yieldsand yield-related traits at maturity. Soaking seeds in PAC improved seedling growth, seedlingsurvival and crown diameter, but decreased the crown length during winter. The most effectiveconcentration of PAC was 4 mg/L and higher concentrations significantly reduced seedgermination rates. Our results demonstrated that rapeseed sown in rice fields after the seeds hadbeen soaked with PAC improved seedling quality at the wintering stage and yield at maturity.

Rhizosphere processes associated with the poor nutrient uptake in no-tillage rice (Oryza sativa L.) at tillering stage

No-tillage (NT) can result in poor nutrient uptake and reduce biomass production in rice (Oryza sativa L.) at early growth stages, but limited information is available on the factors that contribute to the poor nutrient uptake. This study aimed to determine the rhizosphere processes associated with the poor nutrient uptake in NT rice at early growth stages. In field experiments conducted at Changsha, Hunan Province and Nanning, Guangxi Province, China the N, P and K uptake, rhizosphere soil properties and root morphological traits at the tillering stage were compared for rice grown under NT and conventional tillage (CT). The NT rice had 17–43% less N, P and K uptake than did the CT rice. The rhizosphere soil available N, P and K contents were 9–18% greater for the NT rice than the CT rice. The root biomass, surface and length were 7–48% less for rice under NT than under CT. NT rice accumulated 26–37% more pseudomonas than did CT rice in rhizosphere soils. Bioassays indicated that the pseudomonas treatment led to 43–59% reductions in root length, surface and biomass and 39–52% reductions in N, P and K uptake. These results indicate that reduced root growth induced by accumulation of rhizosphere inhibitory pseudomonas was responsible for the poor nutrient uptake in NT rice at the tillering stage. This highlights the need for developing ways to avoid the effect of deleterious soil organisms on NT rice at the tillering stage.

Factors contributing to the superior post-heading nutrient uptake by no-tillage rice

No-tillage (NT) is expected to be an alternative practice for rice production in China since it has potential benefits including labor saving and soil conservation. NT can lead to superior post-heading nutrient uptake and consequently increased post-heading biomass production in rice, but limited information is available on the factors contributing to the superior post-heading nutrient uptake. In this study, post-heading nutrient uptake and related soil and root characteristics were compared between NT and conventional tillage (CT) rice in field experiments in Changsha, Hunan Province of China in 2013 and 2014 and Nanning, Guangxi Province of China in 2014. Results showed that post-heading N, P and K uptake were 28–49% higher under NT than under CT. NT had 10–18% higher available N, P and K contents and 5–9% higher root distribution percentage at 0–5cm soil depth and consequently 11–16% higher rhizophere soil available N, P and K contents than CT. There was no significant difference in rhizophere soil pH between NT and CT. NT had equal root biomass, length and surface but 37–49% higher root oxidation activity compared to CT. These results suggest that improvement in nutrient supply and root physiology are responsible for the superior post-heading nutrient uptake by NT rice.

Effect of Green Manures on Rice Growth and Plant Nutrients under Conventional and No‐Till Systems

Alfalfa (Medicago sativa L.) is a good green manure resource with high N and P concentrations, but its effect on rice (Oryza sativa L.) growth and plant nutrients has not been fully elucidated. Two green manure species, alfalfa and broad bean (Vicia faba L.), and two N fertilizer levels (0 and 200 kg ha−1), alone or in combination, were applied to rice paddy soil under conventional tillage (CT) and no‐till (NT) systems in 2010 and 2011. The results showed that, under CT, alfalfa had a more pronounced effect on increasing grain yield and nutrient content in the grain, plant (leaf N and leaf P), and soil (total N and Olsen P) than broad bean (p &lt; 0.05). Compared with the N fertilizer treatment, the alfalfa treatment alone achieved statistically equivalent levels of grain yield but significantly increased P contents in grain and leaf and Olsen P in soil. The leaf P concentrations at the panicle and grain filling stages had significant positive direct effects and indirect effects via leaf N concentration on grain yield. The effect of alfalfa green manure on the supply of available P to rice was equal between CT and NT systems. The combined treatment of alfalfa and N fertilizer achieved the highest grain yield of all treatments, increasing the yield under CT by 8.58 and 8.21% compared with the N fertilizer treatment in 2010 and 2011, respectively. These results indicate that green manure with a high P concentration is capable of alleviating P deficiency in both CT and NT rice cultivation systems.

No-tillage effect on rice yield in China: A meta-analysis

Rice production in China has been constrained by changes in socioeconomic and physical environments such as decreased labor availability and degraded soil. No-tillage (NT) may be an alternative system for rice production in China because it has potential benefits including labor saving and soil conservation. Here, we conducted a meta-analysis to evaluate the effect of NT on rice yield in China and to investigate how the effect varies with the environmental and management factors. Results showed that decrease in panicle number per unit land area was observed in NT rice across a wide range of environmental and management conditions in China, but grain yield was not reduced because it was compensated for by more spikelet number per panicle and higher spikelet-filling percentage. Grain yield responses to NT were affected by region (climate), soil, cropping system and proportion of N applied during the vegetative period (PNVP). Typically, grain yield showed a positive response to NT in south-west region (where the climate during rice-growing season is characterized by frequent fog and clouds, high humidity and insufficient sunlight). NT resulted in a decreased grain yield in soils with pH lower than 6.0 and low fertility. Grain yield was decreased in rice–rice cropping systems but increased in rice–upland cropping systems by NT. NT had negative effect on grain yield under PNVP of 70% and 80% but had no significant effect under PNVP of 90%. However, responses of grain yield to NT did not vary with establishment method (transplanting vs. seedling throwing vs. direct seeding), cultivar type (hybrid vs. inbred), duration of NT adoption (<3 years vs. 3–6 years vs. >6 years) and residue management practice (removal vs. retention). We conclude that adoption of NT for rice production in China should be site-specific and depend on agronomic practices including cropping system and N management.

Nitrogen Uptake and Utilization by No-Tillage Rice under Different Soil Moisture Conditions – A Model Study under Simulated Soil Conditions

Most of the existing studies regarding water-saving cultivation on rice are based on tillage rice, rather than no-tillage rice. The purpose of this study was to quantify the effects of nitrogen fertilizer on no-tillage rice cultivation undervarious soil moisture conditions, in order to determine the suitable soil moisture content for rice production by no-tillage cultivation. Pot experiments were conducted in the early seasons of 2010 and 2011. In each season, a hybrid rice cultivar, Jiyou716, was planted under the soil moisture contents of 95 – 100% (W100), 80 – 85% (W85) and 65 – 70% (W70). 15N was used as the nitrogen fertilizer. Yield, dry matter accumulation, nitrogen concentration and 15N abundance of maturity were determined for each sample. The nitrogen loss of basal N-fertilizer (BF) and tillering N-fertilizer (TF) in W70 was 22 – 24% and 18 – 45% larger than in W100, respectively, resulting i reduction in nitrogen uptake and total nitrogen accumulation in plants. The yield of rice by no-tillage in W70 was 47 – 42% lower in 2011 and 2010. There was no significant difference between W85 and W100 in yield, nitrogen uptake andutilization in no-tillage cultivation. It was concluded that the N uptake and yield were decreased by decreasing soil moisture contents to 70% of saturation in no-tillage cultivation. Soil content of around 85% was proposed as a suitable condition without a large reduction in the yield and N use in water-saving cultivation, although a field test is essential for practical use.

Changes in soil microbial properties with no-tillage in Chinese cropping systems

No-tillage (NT) has revolutionized agricultural systems because it has potential benefits including soil conservation and reduced production costs though saving in fuel, equipment, and labor. Soil quality is of great importance in determining the sustainability of land management systems, and soil microbial properties are becoming increasingly used to assess the effect of farming practices on soil quality due to their quick response, high sensitivity, ecological relevance, and capacity to provide information that integrates many environmental factors. In China, research and application of NT have developed quickly since 1970s. Numerous studies have been conducted in this country to evaluate the effect of NT on soil microbial properties. From these studies, it is evident that NT can lead to an increase in soil microbial size or activity or both and a consequent increase in soil microbial biomass in upland cropping systems. However, there are still several issues that remain unaddressed or inadequately specified. Further investigations are needed (1) to determine the effect of NT on soil microbial diversity by using molecular biological techniques in both upland and rice-based cropping systems; (2) to fully understand the changes of soil microbial properties with NT in rice-based cropping systems, especially for double rice cropping systems; and (3) to clarify the relationship between rhizosphere microbial properties and crop growth in NT rice cropping systems.

Sistemas de manejo do solo na recuperação de uma pastagem degradada em Rondônia

Na região amazônica, pastagens formadas e conduzidas de forma inadequada perdem a produtividade durante os primeiros anos em razão de superpastejo, ausência de adubação e de manutenção e emprego de espécies inadequadas para as condições edafoflorísticas da região. O objetivo deste estudo foi quantificar as modificações ocasionadas por diferentes sistemas de manejo nos atributos físicos de um Latossolo Vermelho-Amarelo (LVA), sob pastagem degradada no Estado de Rondônia, RO. Os sistemas de manejo utilizados nos tratamentos foram: T = testemunha; G = gradagem + NPK + micronutrientes; H = herbicida + NK + micronutrientes; A = plantio direto de arroz + NPK + micronutrientes; e S = plantio direto de soja + NPK + micronutrientes. O delineamento experimental foi em blocos ao acaso com quatro repetições. Para avaliar os tratamentos, amostras com estrutura indeformada foram coletadas em três profundidades (0-0,10; 0,10-0,20 e 0,20-0,30 m) para determinar a curva de retenção da água no solo, densidade do solo, resistência do solo à penetração de raízes, macroporosidade, microporosidade, porosidade total, estimativa do intervalo hídrico ótimo (IHO), densidade máxima do solo (Dsmax) e densidade relativa do solo (Dsrel). Os sistemas de manejo do solo adotados na recuperação da pastagem não proporcionaram melhorias significativas nos atributos físicos do solo, 40 meses após a implantação dos tratamentos. Em todos os sistemas de manejo, foram encontrados valores de densidade do solo acima do considerado ideal (1,40 Mg m-3) e abaixo do crítico (1,75 Mg m-3). Todos os sistemas de manejo apresentaram valores de densidade do solo relativa (Dsrel) acima do valor adotado como crítico (Dsrel = 86 %), exceto no sistema em que foi realizado o preparo do solo na profundidade de 0-0,10 m. A qualidade física do solo, avaliada pelo IHO, diminuiu com o aumento da profundidade do solo.

免耕稻田氮肥运筹对土壤NH3挥发及氮肥利用率的影响

NH3volatilization is an important process of N loss from fertilizer nitrogen( N) applied to no-tillage rice fields.It has been demonstrated that no-tillage promotes NH3volatilization. However,few studies have been conducted to investigate the effects of N management on NH3volatilization from no-tillage paddy fields. Therefore,a field experiment was conducted on a clay loam soil( Anthrosol,World Reference Base for Soil Resources) to study the effects of N management on NH3volatilization and N use efficiency from no-tillage rice fields in the city of Wuxue in central China during the 2012rice-growing season. In this study,five experimental treatments were arranged in a completely randomized design with three replications. Five treatments were applied including five application rates of N fertilizer in the seedling,mid-tillering,flowering and heading stages of rice: 2∶2∶3∶3( R1),3∶2∶2∶3( R2),4∶2∶2∶2( R3),4∶3∶1∶2( R4) and 0∶0∶0∶0( CK). The NH3volatilization fluxes were determined 20 times using a venting method during the 2012 rice growing season. NH+4concentrations and pH of the soils and field surface water were also measured. The obtained results showed that application of N fertilizer significantly enhanced both NH+4concentrations of the soils and field surface water and the soil pH. Compared with the other fertilized treatments( R2,R3 and R4),R1 significantly decreased NH+4concentrations of the soils and field surface water. In the fertilized treatments,during the rice growing season,each application of N fertilizer led to NH3volatilization fluxes peaking after 1—3 days,and then dropping rapidly to those in the unfertilized treatment levels within1—2 weeks. The NH3volatilization fluxes in the CK treatment were relatively low,and remained nearly unchanged. The NH3volatilization fluxes ranged from 2. 0 to 21. 94 mg·m-2·d-1for the CK treatment and from 2. 21 to 209. 6 mg·m-2·d-1for the fertilized treatments. Mean NH3volatilization fluxes in the R1,R2,R3 and R4 treatments were( 13. 8±2. 0),( 15. 3±0. 2),( 15. 8± 0. 1) and( 14. 2 ± 0. 1) mg·m-2·d-1,respectively,which were 1. 57,1. 81,1. 88 and 1. 69 times,respectively,that in the CK treatment. The cumulative amounts of NH3volatilization were( 8. 52±0. 20)( CK),( 19. 59±2. 30)( R1),( 21. 85 ± 0. 68)( R2),( 21. 98 ± 0. 45)( R3) and( 23. 79 ± 1. 15) kg N / hm2( R4). For fertilized treatments,the highest cumulative NH3volatilization was observed at the mid-tillering stage( accounting for 11. 9% —14. 7% of the total),followed by the heading stage,with the minimum being found at the seeding and booting stages.Compared with no N fertilizer,application of N fertilizer significantly increased NH3volatilization by 56. 5% —64. 2% from the no-tillage paddy fields. In fertilized treatments,N losses through NH3volatilization accounted for 6. 2% —8. 5% of the applied N. Among the four fertilized treatments,the cumulative NH3volatilization was significantly reduced by 9. 1% —17. 7% under R1 than under the other fertilized treatments. Linear correlation analysis indicated that NH+4concentrations and pH in the soils and field surface water were significantly related to the NH3volatilization fluxes. Application of N fertilizer significantly affected N uptake of rice,where,compared with the CK treatments,fertilized treatments significantly increased N uptake of rice by 46. 5% —89. 3%. Compared with the other fertilized treatments,R1 significantly enhanced N use efficiency by 28. 4% —74. 9%. Therefore,our results suggest that N application at the late growth stage of rice can decrease NH3volatilization,thus improving N use efficiency of rice under no-tillage rice fields.

Propriedades físicas do solo e produtividade de arroz irrigado em diferentes sistemas de manejo

O Estado do Rio Grande do Sul é o maior produtor de arroz irrigado do País, com destaque para a região da Fronteira Oeste. O objetivo deste trabalho foi avaliar propriedades físicas do solo e a produtividade de arroz irrigado por inundação em plantio direto e convencional, em níveis de palha residual de arroz em plantio direto. O delineamento experimental foi inteiramente casualizado, com quatro experimentos e 10 repetições nos experimentos 1, 2 e 3 e seis no experimento 4. Os sistemas de manejo foram: experimento 1 (E1), sistema PD (E1PD) e sistema convencional com duas gradagens na camada de 0-7 cm + remaplan (E1C), em área de um ano de cultivo de arroz, após sete anos de pousio do cultivo de arroz e semeadura de azevém no inverno, com pastejo animal o ano todo; experimento 2 (E2), sistema PD (E2PD) e sistema convencional (E2C), após campo nativo; experimento 3 (E3), sistema PD (E3PD) e sistema convencional (E3C), após plantio direto de arroz irrigado durante dois anos em área de campo nativo; e no experimento 4 utilizaram-se quatro níveis de palha residual antes da semeadura do arroz. A produtividade de arroz irrigado por inundação não diferiu entre os sistemas plantio direto e convencional. A massa seca residual do arroz antes da semeadura não influenciou a produtividade de arroz irrigado por inundação.

Effect of tillage on soil and crop properties of wet-seeded flooded rice

No-tillage (NT) is an alternative cropping system for saving costs and conserving soils relative to conventional tillage (CT). However, NT effects on paddy soil and rice growth are still controversial or not fully understood. A fixed field experiment was conducted to compare soil and crop properties between NT and CT wet-seeded flooded super hybrid rice in Changsha, Hunan Province, China. After 6 years of continuous cropping, NT had higher contents of active organic carbon, NaOH hydrolysable N and NH4OAc extractable K and higher activities of invertase, urease and acid phosphatase at 0–5cm soil depth, higher bulk density at 5–10cm soil depth, and higher contents of double acid P at 5–10cm and 10–20cm soil depths. NT or associated soil compaction caused an adverse root environment for NT rice at early growth stage, which resulted in a lower capacity of photosynthetic carbon metabolism and consequent reductions in number of tillers and aboveground biomass accumulation before heading. However, no reductions were observed in total aboveground biomass and grain yield in NT rice, because the negative effects of NT or associated soil compaction on aboveground biomass production before heading were compensated for by its positive effects on aboveground biomass accumulation after heading. On one hand, the reduction in growth before heading of NT rice made its population density lower but more suitable during heading to 20 days after heading, which led to a more appropriate leaf area index, a lower leaf senescence and a consequent increase in net assimilation rate. On the other hand, N uptake was delayed in NT rice, which was another critical factor in determining its low leaf senescence. Our study suggests that the negative effects of NT or associated soil compaction on crop growth at early growth stage do not necessarily become concerns in NT wet-seeded flooded rice production.

Short-term effects of conservation management practices on soil labile organic carbon fractions under a rape–rice rotation in central China

Conservation management practices, such as no-tillage (NT) or crop residue mulch, alter soil organic carbon (C) lability, thus affecting soil quality. However, inconsistent effects of conservation management practices on soil labile organic C have been commonly reported. We hypothesized, however, that conservation management practices can improve soil labile organic C fractions and then C management index (CMI) and soil quality. Thus, our objective was to quantify labile organic C contents on a clay loam soil (Anthrosols, World Reference Base for Soil Resources) 3 years after implementing four tillage/crop residue management treatments under a rice Liangyoupeijiu (Oryza sativa L.)–rape Huayouzaliuhao (Brassica napus) rotation in Wuxue City of central China. The experiment included four treatments: (1) single conventional tillage (CT) without crop residue (rape with NT–rice with CT); (2) double CT without crop residue (rape with CT–rice with CT); (3) double NT without crop residue (rape with NT–rice with NT); and (4) double NT plus crop residue (rape with NT+rice residue mulch–rice with NT+rape residue mulch). Five soil organic C fractions were determined from 0 to 30cm layer in October 2009 (3 years after a rape–rice double crop rotation). Total organic C, microbial biomass C, dissolved organic C, particulate organic C, easily oxidizable C, and water stable aggregation were measured. A CMI was also calculated. The concentrations of total organic C, microbial organic C, dissolved organic C, and particulate organic C under the double NT plus crop residue treatment were 1.07–1.17, 1.20–1.26, 1.08–1.30 and 1.17–1.76 times higher than those under the other three treatments. The total organic C and labile organic C contents under the double NT with or without crop residue treatment were generally higher at 0–5cm than at greater sampling depths. The proportions of 0.5–2mm water-stable aggregates at the 0–5cm depth under the double NT with or without crop residue treatment were significantly greater (P<0.05) than those under the single or double CT without crop residue treatment, but lower (P<0.05) at the 5–30cm depth. Soil labile organic C fractions were positively correlated with each other. The greater C pool index (CPI) at the 0–5cm depth observed under double NT with or without crop residue treatment compared to single or double CT without crop residue treatment led to greater CMI at the same depth. However, CMI at the 5–30cm depth was lower for the double NT with or without crop residue treatment compared to the single or double CT without crop residue treatment. Thus, our results indicated that soil labile organic C fractions were only sensitive to changes in management practices in the upper soil profile, and that short-term effects of continuous NT or NT with crop residue mulch in a rape–rice rotation system appeared to only improve soil quality in the upper soil profile. Based on these results, we suggested that greater quantities of labile organic C can be concentrated in the 0–30cm soil layer of a soil under rape–rice rotation by more sustainable practices than those currently being used in central China.

Effects of Nitrogen Application on Agronomic Traits and Yield of Rapeseed in No-tillage Rice Stubble Field

To investigate the effects of various nitrogen applications adapted to direct-seeding rapeseed on agronomic perform-ances and grain yields in no-tillage rice stubble field,we used the rapeseed cultivar Huaza 9 in plot experiments under the no-tillage direct-seeding and transplanting cultivations during 2006-2010.It was observed that a top-dressing applied during the duration of stem extension increased grain yield under various base manure application rates.When two top-dressing were used during the growth of the rapeseed plants,effects of fertilizer applications on yield formation depended on application date and amount of base manure.When base manure application rate was 112.5 kg N ha-1,the high grain yields were obtained with the top-dressing applied for the stem extension and flowering,respectively.However,in the condition that the base manure applica-tion rate was 202.5 kg N ha-1,the high grain yields were gained when the mid-December fertilizer and stem-extension fertilizer were applied.On the other hand,when the base manure and top-dressing fertilizers were setting at the ratio of 5:5,the high grain yields were observed for both direct-seeding and transplanting rapeseeds,independent of the amount of nitrogen application.The results also showed that the mentioned four modes for nitrogen application significantly decreased the amount of N-fertilizer and increased the grain yields under both no-tillage direct-seeding and transplanting cultivations.

무경운 피복작물 작부체계가 벼 뿌리 생육에 미치는 영향

무경운 논에서 피복작물로 자운영, 볏짚, 헤어리베치, 유채, 호밀 등을 처리하고 토양 깊이별 벼 뿌리의 생육상황과 활성 유기물 함량을 조사하였다. 벼 생육초기 주당 발근량은 무경운 유채 처리구가 256 cm로 가장 양호하였으며 무경운 자운영 처리구는 214 cm, 관행은 176 cm, 무경운 헤어리베치 처리구는 139 cm, 무경운 호밀 처리구는 106 cm, 무경운 녹비무처리는 104 cm, 무경운 볏짚 처리구는 99 cm 순으로 나타났다. 토양 깊이 0-5 cm에서 무경운 볏짚 처리구에서 <TEX>$128g\;m^{-2}$</TEX>로 다른 처리구에 비해 유의적으로 높았다 (p<0.05). 무경운 자운영 처리구도 <TEX>$83.5g\;m^{-2}$</TEX>로 무경운 볏짚 처리구를 제외한 다른 처리구에 비해 유의적인 차이를 보였으며 무경운 헤어리베치 처리는 <TEX>$53.0g\;m^{-2}$</TEX>으로 가장 낮았다. 토양 깊이별 활성 유기물 함량은 0-5 cm 에서 무경운 자운영 처리구가 <TEX>$1,684g\;m^{-2}$</TEX>으로 가장 많았으며 무경운 유채 처리구 <TEX>$1,309g\;m^{-2}$</TEX>, 무경운 볏짚 처리구 <TEX>$1,295g\;m^{-2}$</TEX>, 무경운 호밀 처리구 <TEX>$1,072g\;m^{-2}$</TEX>, 무경운 헤어 리베치 처리구 <TEX>$917g\;m^{-2}$</TEX> 순이었고 관행은 <TEX>$434g\;m^{-2}$</TEX>, 무경운 녹비 무처리구는 <TEX>$426g\;m^{-2}$</TEX>으로 매우 낮은 함량을 보였다. 본 연구결과 무경운 피복작물 작부체계에서 볏짚 처리구와 자운영 처리구는 벼 뿌리 생육과 활성 유기물 함량을 증대시키는 것으로 판단되었다. This study was conducted to evaluate the effect of rice cover crop cropping systems on rice root growth in a rice field as affected by conventional tillage without rice straw or green manure crop treatment (CTFS, check plot), no-tillage without cover crops (NTNT), no-tillage amended with rape (NTRA), no-tillage amended with rye (NTRY), no-tillage amended with hairyvetch (NTHV), and no-tillage amended with Chinese milk vetch (NTCM). In 0-5 cm soil depth, dry weight of root in NTRS (<TEX>$128g\;m^{-2}$</TEX>) was significantly higher than in the other plots (p<0.05) at harvesting stage. In addition, content of active organic matter at 0-5 cm soil depth was <TEX>$1,684g\;m^{-2}$</TEX> in NTCM, <TEX>$1,309g\;m^{-2}$</TEX> in NTRA, <TEX>$1,295g\;m^{-2}$</TEX> in NTRS, <TEX>$1,072g\;m^{-2}$</TEX> in NTRY, <TEX>$917g\;m^{-2}$</TEX> in NTHV, <TEX>$434g\;m^{-2}$</TEX> CTFS, and <TEX>$426g\;m^{-2}$</TEX> in NTNT treatment. In no-tillage rice cover crop cropping system, our findings suggest that NTRS and NTCM should be enhanced root growth and active organic matter in paddy field.

Effect of Planting Method on Grain Quality and Nutrient Utilization for No-Tillage Rice

Field experiments were conducted over 2 years using six rice (Oryza Sativa L.) cultivars to investigate the effect of two planting methods, transplanting (TP) and direct sowing (DS), on grain quality and nutrient utilization. Brown and head rice percentages, grain width, amylase, and protein content were greater in TP than in DS, whereas the opposite effect was found for chalkiness rate, gel consistency, and alkali spread value (ASV). Dramatic differences were also found between the two planting methods for nutrient harvest index and utilization efficiency, with TP having greater phosphorus (P) and potassium (K) harvest indexes, nitrogen (N) and K utilization efficiencies, and lower N harvest index and P utilization efficiency than DS. Moreover, significant differences between these genotypes could be found for both nutrient harvest index and utilization efficiency. The correlation analysis showed that rice chalkiness, transparency, gel consistency, amylose, and protein contents were all significantly correlated with N, P, and K nutrient traits. In addition, significant interactions between rice cultivar and planting methods for both rice quality and nutrient traits were also found.