Intense fragmentation and deep burial reduce emergence of Rumex crispus L.

Abstract

Mechanical control through different tillage methods is a common measure against perennial weeds. However, non-optimal tillage can potentially increase the vegetative regeneration instead of reducing it. Aspects of regenerative capacity in the perennial weed species Rumex crispus L. was studied in three pot and box experiments as follows: (1) regeneration from different root fragments under varying test conditions; (2) effects of root size and burial depth on time of emergence and emergence rate; and (3) effects of burial depth and cutting on biomass production and seed production. In experiment 1, sprouting occurred mainly from the neck of the roots, consisting of underground stem tissue. A few shoots were observed also from the upper half of the true taproot and from a side root. No difference in sprouting was found between test conditions. In experiment 2, total emergence rate was positively related to root size and negatively related to burial depth. Time to first emergence was defined by an interaction between the two factors. Roots larger than 100 g gave rise to a high degree of emergence from all burial depths, while emergence from roots weighing 20–30 g was less than 30% from 12 cm and nonexistent from 18 cm. When emergence and shoot production were tested under different cutting regimes (experiment 3), the separated top fragments of the roots sprouted faster and produced more shoot biomass than intact rootstocks, even at a second harvest. Our results indicate that fragmentation can stimulate sprouting from the regenerative tissue of the taproot. Hence, if tillage is carried out as weed control it is important that root fragments are buried at ploughing depth, especially if the population consists of adult plants.     

Changes in the weed communities as affected by different primary soil tillage and deep loosening

Long-term soil cultivation at the same depth affects soil characteristics and crop productivity. The aim of the study was to investigate the impact of a long-term different intensity soil tillage methods and deep loosening on weed number, weed agrobiological group and soil seed bank changes in till Bathygleyic Dystric Glossic Retisol soil under the climatic conditions of the Western Lithuania (geographical coordinates 55°43′38″N, 21°27′43″E). The study included different soil tillage methods (conventional ploughing, shallow ploughing and shallow ploughless tillage) and deep loosening. During investigational years, the greatest weed number in crops and the greatest weed seed number in the seed bank were determined in the soil reduced tillage (shallow ploughing and shallow ploughless tillage). The weed number in crops of conventional ploughing soil was 35.8% lover compared to reduced tillage soil. The weed seed number in the seed bank of conventional ploughing was 49.6% lover compared to reduced tillage Decreasing soil tillage intensity resulted in weed seeds concentration in the upper topsoil. A one-time deep loosening had a significant effect during the crop rotation: the weed number in crops and weed seed number in the seed bank were determined to have increased by 26.6% and 51.6% in conventional ploughing soil and by 11.9% and 23.2% shallow ploughless soil respectively. However, after deep loosening, the number of Poa annua in crops decreased 2.9 times in plots of conventional ploughing and 1.7 times – in plots of shallow ploughing soil.     

Residue cover,soil structure,weed infestation and spring cereal yields as affected by tillage and straw management on three soils in Norway

Four field trials (spring wheat and oats) were conducted (one on clay soil, one on loam soil and two on silt soil) for three years in important cereal growing districts, to investigate the influence of tillage regimes (ploughing versus reduced tillage in either autumn or spring) and straw management (removed and retained) on plant residue amounts, weed populations, soil structural parameters and cereal yields. The effect of tillage on soil structure varied, mainly due to the short trial period. In general, the amount of small soil aggregates increased with tillage intensity. Reduced soil tillage, and in some cases spring ploughing, gave significantly higher aggregate stability than autumn ploughing, thus providing protection against erosion. However, decreasing tillage intensity increased the amounts of weeds, particularly of Poa annua on silt soil. Straw treatment only slightly affected yields, while effects of tillage varied between both year and location. Reduced tillage, compared to ploughing, gave only small yield differences on loam soil, while it was superior on clay soil and inferior on silt soil. Our results suggest that shallow spring ploughing is a good alternative to autumn ploughing, since it gave comparable yields, better protection against erosion and was nearly as effective against weeds.     

Time of seed collection and germination in rocket, Erucavesicaria (L.) Cav. (Brassicaceae)

The increasing importance of rocket Erucaspp. as a leaf and oil crop, and especially as a Fourth Generationvegetable, calls for a better understanding of several basic aspectsof its biology. Knowledge on seed germination behaviour is necessaryto optimize the management of the plant in the field and inseedbanks. Seed germination of several samples of rocket was assayedin the laboratory under different incubation conditions. Germinationin the two studied populations was fairly high, ranging from68% to 96%. However, remarkable variation was foundwithin one of them according to the date of collection of the sample,ranging from 78–96% for those collected in summer(LG1 and LG2) to 21–29% for that collected inautumn (LG3). Neither time of storage nor GA₃treatments had any significant effect on this low percentage, whichcould only be significantly improved with scarification, up to47% by dry heat and up to 66% by immersion in liquidnitrogen. Dormancy and low seed viability probably originating fromeffects of environmental factors during seed formation and maturationseem to play a role in the low germination percentage of sampleLG3.     

Foliar spray of mineral nutrients enhanced the growth,seed yield,and quality in onion (Allium cepa L.) cv. Pusa Riddhi

The present experiment was conducted to investigate the effect of foliar spray of mineral nutrients on plant growth, seed yield, and quality attributes in onion cv. Pusa Riddhi at SPU, IARI, New Delhi during rabi 2013–14 and 2014–15. The experiment consisted of 16 treatments comprised of boron, zinc, calcium, and magnesium laid out in a completely randomized block design with two replications. The study revealed that the foliar zinc spray (625 g ha^?1) produced higher seed scape height (105.35 cm) along with lower disease incidence (8.50%) than the other treatments. Whereas, higher number of seed scapes plant^?1 (11.20) and productive seed scapes plant^?1 (8.58) were observed in T₁₀ (500 g ha^?1) and combined spray of B + Zn + Ca (T₁₄), respectively. The flowering traits, viz., umbellates umbel^?1 (642.45), productive umbellates umbel^?1 (579.35), and umbel diameter (7.38cm) were significantly (p ≤ 0.05) higher in T₁₅ than other treatments. Similarly, higher seed yield and seed quality attributes were also observed in combined application of all minerals treatment (T₁₅).     

不同施肥及杂草处理下半湿润冬小麦田NO3——N的动态变化

以中等肥力土垫旱耕人为土为供试土壤,在冬小麦（Triticum aestivum）不同生育期采集0-100 cm土层土壤样品,研究不同施肥及杂草处理对半湿润农田生态系统土壤NO3--N动态变化的影响。结果表明,1）土壤剖面NO3--N含量随施氮量增加而显著增加,0-100 cm土层NO3--N累积量与施氮量线性相关;在越冬期、返青期和拔节期,相关系数r分别为0.995、0.971和0.949。2）冬小麦生长过程中,土体NO3--N含量先降低后回升,在拔节期最低;成熟期土壤有机氮矿化产生的NO3--N是收获后土壤剖面残留NO3--N的主要贡献者。3）在越冬期、返青期、拔节期和成熟期,施磷（PN135）与不施磷（P0N135）处理相比,施磷可显著减少土体NO3--N累积量,减少量分别为N 61.4、26.9、36.6和5.5 kg/hm2;磷肥对减少土壤NO3--N残留累积量的影响以越冬期表现最为显著,成熟期表现不显著。4）在施磷的基础上,不同杂草处理土壤剖面NO3--N累积量在每公顷施氮45 kg（PN45）及施氮90 kg (PN90)时存在一定差异,但不显著;而在每公顷施氮180 kg（即PN180）的高氮处理下,差异显著。每公顷施氮135 kg（PN135）,的中氮处理,在越冬期清除杂草后土壤剖面中NO3--N累积量在拔节期显著高于其它杂草处理。     

Stabilization of lead as affected by various amendments and incubation time in a calcareous soil

The effect of different kinds of amendments including coal fly ash (CFA), municipal solid waste compost (MSWC), rice husk biochars prepared at 300°C (B300) and 600°C (B600), zero valent iron (Fe°) and zero valent manganese (Mn°) were evaluated to determine their ability to stabilize lead (Pb) in Pb-spiked soil. The Pb-spiked soils were separately incubated with amendments at the rates of 2 and 5% (W/W) for 45 and 90 days at 25°C. The efficacy of amendments treatment was evaluated by desorption kinetic experiment and sequential extraction producer. According to the results, with increasing time, considerable changes in distribution of chemical forms of Pb occurred and carbonate-bound fraction significantly decreased, while amorphous Fe-bound fraction significantly increased. The applied treatments efficiently decreased the mobility factor of Pb compared to control treatment. Application of Mn°, Fe°, CFA, MSWC, and B600 in soils significantly decreased Pb desorption rate with respect to control treatment. Biphasic pattern of Pb desorption kinetic was fitted well by the model of two ?rst-order reactions. In general, present study showed that from the practical point of view, all applied amendments (except for B300) were effective in Pb immobilization; however, application of Mn° at 5% (W/W) rate was the best treatment to immobilize Pb, so it can be recommended for the immobilization of Pb in calcareous polluted soil.     

Physical and mechanical properties of a clayey soil as affected by tillage systems for wheat growth

Abstract

The effect of tillage systems on soil physical properties of a clayey soil was studied. Tillage systems consisting of conventional tillage I (CT₁), conventional tillage II (CT₂), reduced conventional tillage (RCT), reduced tillage (RT) and no tillage (NT) were carried out in autumn after harvest of sugar beet. Significant differences between tillage systems were recorded on the measured properties, apart from moisture content, at 15–30 cm soil layer. The CT₁, CT₂ and RCT systems resulted in similar penetration resistance and bulk density values below the 15 cm soil depth, while the RT and NT systems resulted in higher but similar values. The mean penetration resistance values were less than 1 MPa in the CT₁, CT₂ and RCT systems at the 0–15 cm depth, while they were 1.41, 1.84 MPa in RT and NT, respectively. The mean total porosity increased with tillage from 8.2 to 28% when compared with NT. The CT₁, CT₂ and RCT systems resulted in lower moisture content at the 0–15 cm depth. The lowest moisture content occurred in RCT (24.4%) and the highest in NT (30.9%), while it was 30.3% in RT system. The lowest and highest mean weight diameter values were reported for the RT (1.36 mm) and NT (2.37 mm) systems, respectively. The lowest wheat grain yield was obtained in NT (4.14) and the highest in CT₁ (5.24 Mg ha^?1). A significant difference occurred between only NT and the other systems. When both grain yield and advantages of reduced tillage are considered, the RT system is recommended.     

Immediate Effects of Time and Method of Alfalfa Termination on Soil Mineral Nitrogen,Moisture, Weed Control,and Seed Yield,Quality, and Nitrogen Uptake

Three field experiments were conducted on Gray Luvisol (Typic Cryoboralf) soils in northeastern Saskatchewan to compare the effects of alfalfa (Medicago sativa Leyss) stand termination with tillage and herbicides at different times on mineral nitrogen (N) (ammonium-N and nitrate-N) and moisture content of soil in spring (experiments 1 and 2), soil moisture, volunteer alfalfa and dandelion control, plant density, seed yield, protein concentration and N uptake for wheat (Triticum aestivum L.), barley (Hordeum vulgare L), canola (Brassica rapa L.), and pea (Pisum sativum L.) crops (experiment 3). Termination treatments included combinations of times (in mid-June after cut 1, in mid-August after cut 2 and in mid-May during spring) and methods [tillage alone, herbicides alone (glyphosate + 2,4-D amine and also clopyralid + 2,4-D ester in experiment 3) and these herbicides + tillage]. Tillage alone significantly increased spring soil nitrate-N levels over herbicides alone or herbicides + tillage. Termination after cut 1 had the highest levels of soil nitrate-N. There was little effect of time and method of termination on soil ammonium-N and moisture content in spring. Herbicides + tillage generally provided better control of both volunteer alfalfa and dandelion in the four crops than tillage or herbicides alone. In general, alfalfa termination with herbicides alone significantly reduced plant density, seed yield, and N uptake of all crops and protein concentration of cereals only due to effects on levels of soil nitrate-N, dandelion control, and crop injury by clopyralid or 2,4-D residues in soil. Plant density, seed yield, N uptake and protein concentration of crops tended to decline with delay in termination time. The results of this study support the use of some tillage in alfalfa stand termination in helping to control volunteer alfalfa and dandelion and optimize annual crop yields and quality.     

Sesame (Sesame indicum L.) biochemical and physiological responses as affected by applying chemical,biological, and nano-fertilizers in field water stress conditions

Abstract

Co-application of nano, chemical, and biological fertilizers has been recommended to increase quality and quantity of plants in sustainable production systems. Field experiments (factorial split plot experiment based on completely randomized block design) were conducted during two consecutive years to investigate the effect of nitrogen (nitroxin, urea, and nitroxin + 50% urea) and potassium (without fertilizer, soil and foliar application of potassium nano-chelate, and potassium dioxide) forms on grain yield, physiological traits, oil content, and fatty acids composition of sesame under water stress conditions (normal irrigation, irrigation up to 50% seed ripening and flowering (mild and severe stresses, respectively). Severe water stress was caused decreasing chlorophyll content, grain yield (25.4%), seed oil content (2.87%), and unsaturated fatty acid content, while it increased catalase and peroxidase activities, total carbohydrate, and saturated fatty acids content in compared to the control. As shown, the grain yield in the second year was more than the amount in the first year. The highest grain yield was achieved in co-application of 50% urea and nitroxin in combined with potassium dioxide under normal irrigation during the second year, which showed an increase of 42%, compared to the control treatment. Application of potassium fertilizer (nano or chemical) increased unsaturated fatty acids content in compared to the control treatment. While non-application of fertilizer had the highest saturated fatty acids content. Finally, the co-application of potassium fertilizer (nano or chemical forms) with nitrogen fertilizer (nitroxin + 50% urea) could alleviate the adverse effects of water stress on the studied traits.     

Quality,yield and nitrogen fixation of faba bean seeds as affected by sulphur fertilization

Abstract

Faba bean (Vicia faba L.) is an important source of plant protein for humans and animals; however, nutritional value of seeds is notoriously deficient in sulphur (S)-containing amino acids. In this article, the effect of S fertilization on faba bean's capability of N₂ fixation, grain yield and chemical characteristics in terms of protein fractions, fatty acids and minerals composition is reported. A randomized, complete block design with three replicates was used, and three S applications (0, 30 and 60 kg ha^?1, respectively) for faba bean were performed. The S fertilization was split into two applications: 50% before sowing and 50% in the beginning of March as K₂SO₄. At the same time, both the legume and oat crops were fertilized uniformly with 10 kg N ha^?1 as ¹⁵N NH₄ ¹⁵NO₃ (10% ¹⁵N atomic excess) in solution form. In a Mediterranean climate under optimal spring rainfall situations, faba bean produced high yield of grain and protein. Sulphur application resulted in an increase in overall plant yield and N₂ fixation. In addition, S fertilization enhanced the protein quality, increasing its degradable fraction. Fertilizing faba bean with 30 kg ha^?1 of S resulted in a more appropriate dose in order to obtain a quantitative and qualitative crop improvement. From our findings, it can be concluded that S fertilization to faba bean should be recommended to soils with suboptimal S levels to obtain maximum seed and protein yields.     

Diffusive fluxes of phosphorus,potassium and metallic microelements as affected by soil compaction

ABSTRACT

The objective was to evaluate the effects of soil compaction on phosphorus (P), potassium (K), zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) diffusive fluxes. The experiment consisted of two Oxisols and eight compaction pressures. The soil samples were placed in diffusion chambers, simultaneously with two ion-exchange membranes (anionic and cationic), compressed and incubated for 20 days. The P, K, Zn, Cu, Fe, and Mn diffusive fluxes (PDF, KDF, ZnDF, CuDF, FeDF, and MnDF) were determined. The compaction decreased the PDF in the oxidic-gibbsitic soil, and increased KDF, ZnDF, CuDF, and MnDF, in both soils. There was a higher diffusion of Zn, Cu, and Mn in the kaolinitic than the oxidic-gibbsitic soil. The descending order of cationic-microelement diffusive flux was MnDF > ZnDF ? FeDF > CuDF. Presumably, Fe was mainly diffused as organic complexes with net negative charges, whereas Zn and Mn as free ions and, or, inorganic and organic complexes with positive charges.

Abbreviations: CuDF, cupper diffusive flux; FeDF, iron diffusive flux; KDF, potassium diffusive flux; MnDF, manganese diffusive flux; PDF, phosphorus diffusive flux; ZnDF, zinc diffusive flux; AEM, anion-exchange membrane; CEM, cation-exchange membrane     

Effects of seed priming, aggregate size and soil matric potential on emergence of cotton (Gossypium hirsutum L.) and maize (Zea mays L.)

Poor crop establishment, due to poor land preparation methods and inadequate soil moisture, continues to be a major constraint to crop production for smallholder farmers in the semi-arid tropics. On-farm seed priming (soaking seed in water) has been offered as a solution to this problem, but the ways in which this technology interacts with soil conditions are not well understood. The interactions between seed priming and soil physical conditions on cotton (Gossypium hirsutum L.) and maize (Zea mays L.) emergence and seedling growth were determined in laboratory pot experiments. The treatments included seed treatment (primed and non-primed), initial soil matric potential (−10, −50, −100, −200 and −1500 kPa) and aggregate size (<1, 1–2, 2–4.75 and 4.75–16 mm). Non-sieved soil was used as a control. The soil used (a Chromic Cambisol) was collected from Save Valley Experiment Station in the southeastern lowveld of Zimbabwe. The pots of soil were allowed to dry out after planting, to simulate a deteriorating seedbed. Emergence was subsequently monitored, and plant growth measured 8 days after planting. Final percent emergence and seedling growth decreased with initial matric potential but increased with priming in both crops. Large aggregate sizes generally had an adverse effect on emergence and growth. The data are consistent with the hypothesis that on-farm seed priming can partly compensate for the negative effects of low soil matric potential and large aggregate sizes on crop establishment.     

长期施肥对中国亚热带水稻土土壤稳定性和机械属性的影响

Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.     

Changes in recovery of native and applied phosphorus with time as affected by soil properties in some calcareous soils

In an attempt to investigate variations in availability of native and applied phosphorus (P) with time, twenty five calcareous soil samples were treated with 0, 50 and 500 mg P kg^?1 soil and incubated at 80–90% of field capacity moisture content in an open door glasshouse for a period of one year. Soil samples were taken out at certain intervals for P extraction with Olsen extractant under moist condition. Results indicated that following wetting the mean value of native Olsen-P decreased initially and then increased gradually with time of incubation. Generally, the short term (24 h) recoveries were not correlated with long term ones. The recovery of added P with time was described properly by the following new proposed model: R = 100/(1 + kt^b), where R is percent recovery at time t, and k and b are empirical parameters. The values of k constant at 50 and 500 mg P kg^?1 were in the ranges of 0.40 to 1.22 (0.84 ± 0.25, on average) and 0.04 to 0.52 (0.23 ± 0.14, on average), respectively. The corresponding respective values of b constant also ranged from 0.05 to 0.32 (0.15 ± 0.06, on average) and 0.12 to 0.92 (0.46 ± 0.23, on average).     

红壤交换性钙、镁和钾的分布及施肥对其影响

A leaching experiment was Carried out with repacked soil columns in laboratory to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices.The treatments were CK(as a control),CaCO3,CaSO4,MgCO3,Ca(H2PO4)2,Urea,KCl,Multiple(a mixture of the above mentioned fertilizers) and KNO3,The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through perstaltic pumps over a period of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles ,i.o.,of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles,I.e.0-5cm,5-10cm,10-20cm,20-40cm,and 40-60cm,The results showed when applying Ca,Mg,and K to the bare surface of the soil columns,exchangeable Ca^2 ,Mg^2 ,and K^ in the upper layer of the soil profile increased correspondingly,with an extent depending mainly on the application rates of Ca,Mg,and K and showing a downward trend,CaCO3,CaSO4,MgCO3,and Ca(H2PO4)2 treatments had scarcely and effect on movement of exchangeable K^ ,while CaCO3,and CaSO4 treatments singnificantly promoted the downward movement of exchangealble Mg^2 although these two treatments had no obvious effect on leaching losses of Mg,The fact that under Urea treatment,exchangeable Ca^2 and Mg^2 ,were higher as compared to CK treatment showed urea could prevent leaching of exchangeable Ca^2 and Mg^2 ,the obvious downward movement of exchangeable Ca^2 and Mg^2 was noticed in KCl treatment ,In Multiple treatment,the downward movement of exchangeable Ca^2 and Mg^2 was evident,while that of K^ was less evident,Application of KNO3 strongly promoted the downward movement of exchangeable Ca^2 and Mg^2 in the soil profile.     

Plant,grain, and soil response of irrigated malt barley as affected by cultivar,phosphorus, and sulfur applications on an alkaline soil

Information on the effects of phosphorus (P) and sulfur (S) applications on crop response and soil-P status of two-row malt barley (Hordeum vulgare L.) under high-input conditions are limited in alkaline soils despite widespread fertilizer-P and -S use. A field study was conducted during the 2015 and 2016 growing seasons where the barley cultivars (ABI-Voyager and Moravian 69) were grown at five rates of P (0, 37, 73, 110, and 147?kg P ha^?1) and three rates of S (0, 112, 224?kg S ha^?1). ABI-Voyager had significantly greater biological yield (17,023?kg ha^?1) and grain yield (7433?kg ha^?1) but a lower (44%) harvest index (HI) than Moravian 69 (15,037?kg ha^?1, 7168?kg ha^?1 and 49%, respectively). Grain yield increased with rate of P-application until 37?kg P ha^?1 where the maximum calculated yield was obtained at 98?kg P ha^?1 by a quadratic model. Sulfur application had no significant effect on any of the measured crop or soil parameters. Olsen P increased linearly with greater fertilizer-P applications, indicating grain-P removal was not sufficient to reduce or retain STP concentrations at initial levels when P was applied. Crop-P uptake and soil-P response to fertilizer P applications are important, as remaining soil P is available for subsequent crop usage and may have potential negative environmental impacts. Thus, cultivar selection and appropriate fertilizer-P and S management will ensure optimal agronomic and economic returns while minimizing potentially negative environmental impacts for two-row malt barley produced in the western United States.     

Aggregate stability of a silt loam soil as affected by roots of corn,soybeans and wheat

Abstract

A greenhouse experiment was conducted to investigate the effect of root growth and exudation of 3 crop species on soil aggregation. Two plant populations for each of 3 crops (corn, soybeans, and wheat) were grown in a Fincastle silt loam for 5 time periods (7, 14, 21, 28, and 41 days) and compared with fallow controls. Aggregate stability was estimated by the wet‐sieve method on both initially moist and air‐dry samples.

Soil water content of initially moist soil samples varied widely among replicates, crops, and sampling dates. Wet‐sieving using initially moist soil showed that samples with higher initial soil water content had greater aggregate stability. Wet‐sieving performed on initially air‐dry soil samples was used for subsequent interpretation because the water content variable was removed.

The presence of any crop and its roots in the planted soils versus the fallow controls was associated with increases in aggregate stability. No differences in aggregate stability were found among the different crops or over the established range of root length densities. Aggregate stability decreased from the original level during the first 14 to 21 days of the experiment, possibly due to daily watering. After 21 days, as root growth continued to increase, restabilization occurred until the original aggregate stability of the soil was exceeded for all crops. The observed increase in aggregate stability may be due in part to the physical entanglement of aggregates by roots and to the increased production of root exudates resulting from increased root growth.     

Maize (Zea mays L.) yield and soil properties as affected by no tillage in the black soils of China

A four-year tillage experiment on maize was conducted in the high latitude region of Northeast of China. The main objective of this study was to investigate the effects of different field tillage practices on maize grain yield, soil physical properties, and soil water and temperature dynamics in Northeast of China. The tillage practices included moldboard plow tillage (MOT), rotary tillage (ROT), reduced tillage (RET), combined tillage (COT), and no tillage (NOT). The surface soil water content at depths of 0–20 cm was higher under NOT compared with other tillage practices, but not different at the deeper soil depths in 2011. The soil temperatures under NOT and RET were lower than those under moldboard plow tillage and ROT at depths of 5 and 15 cm, respectively, measured at 9:00 am in 2005. From the hourly dynamics of soil temperature, the differences among the tillage practices mainly appeared during the daytime (from 8:00 am to 7:00 pm). Among all the practices, the average daily soil temperature under ROT was the highest, while that under NOT was the lowest. MOT, ROT, and RET had higher soil accumulative infiltration compared with NOT and COT. The surface soil bulk density under NOT was higher than or equal to that under the other four tillage practices. The maize yields under NOT were the lowest among all the tillage practices for three years straight. Meanwhile, the yields under MOT were the highest, which were about 47%, 61%, and 38% higher than those under NOT. NOT practice is not recommended for use in spring-planted maize under the high latitude humid cool climate Mollisol region in Northeast of China.