Forage and Food Legumes in a Multi‐Year,Wheat‐Based Rotation Under Drought‐Stressed Conditions in Northern Syria’s Medium Rainfall Zone

Long‐term crop rotation trials were designed to assess sustainability of alternatives to traditional fallow and monocropping. The trial described here (6 years) involved wheat (Triticum aestivum L.) in rotation with lentil (Lens culinaris L.), forage vetch (Vicia sativa), pasture medic (Medicago spp.), fallow and watermelon (Citrullus vulgaris). Barley (Hordeum vulgare L.) was compared with wheat for an additional 2 years. Cereal grain and straw yields were highest with fallow and watermelon followed by vetch, lentil and medic; the latter showed no differential effect of variable grazing intensity. Fertilizer N increased yields except in the low‐rainfall years (less than 250 mm). Barley out‐yielded wheat in terms of grain, but not straw. Medic yielded highest in dry matter, whereas lentil produced highest seed yield. Despite the difficulty of assessing crop and animal‐oriented rotations because of non‐commonality of outputs, economic considerations are foremost, but other benefits of rotations (soil quality, water‐use relations) are also relevant to the overall assessment of cereal‐based Mediterranean rotations. The study suggested barley rather than wheat as the desired cereal in rotation with legumes in this marginal‐rainfall (350 mm) environment and provided support for the viability of vetch and lentil in the cropping system. Given the importance of sheep in the region’s farming system, vetch is likely to have a major role in crop rotations.     

Effects of tillage,crop systems and fertilization on weed abundance and diversity in 4-year dry land winter wheat

The arable fields in central Spain have been dominated by cereal production, especially winter wheat. In this area, the defined action of weed management program requires a clear understanding of the factors and mechanisms conditioning weed community dynamics in agro systems. This study evaluated the effects of different agricultural management systems on the abundance and diversity of weed communities in winter wheat crops.Weed density and composition of weed species were sampled over four years; comparing monoculture wheat and rotational wheat in three agricultural management systems: (1) direct drilling (no-tillage, NT); (2) chisel ploughing (minimum tillage 15 cm depth, MT) and (3) mouldboard ploughing (traditional tillage 20 cm depth, CT). With the aim to be able to improve weed management in agro systems with semiarid environments; within each of the agricultural management systems, we examined the impact of mineral fertilization (traditional and balanced) as a tool for reducing the external inputs in arable cereals.Weed diversity was assessed using the three common diversity indices: Shannon's index, evenness index and species richness. The data collected showed total weed density was different per tillage system and each year of the study, but we did not find significant differences between crop systems over the study.The abundance, diversity and evenness of the weed community in the arable field, were significantly increased in NT systems. Within the direct drilling (NT) plots, rotational wheat showed the highest levels of weed infestation and diversity. Comparing traditional and balanced mineral fertilization of soil did not reveal a significant effect on weed abundance and diversity observed in field.     

Effects of reduced tillage on soil surface properties affecting wind erosion in semiarid fallow lands of Central Aragón

In Central Aragón (NE Spain), where strong and dry winds are frequent all year round, fallow lands are susceptible to wind erosion due to insufficient crop residues on the surface and loose, finely divided soils by multiple tillage operations. Effects of conventional tillage (CT — mouldboard ploughing followed by a compacting roller) and reduced tillage (RT — chisel ploughing) on soil surface properties affecting wind erosion were studied during three experimental campaigns in a dryland field of Central Aragón. RT provided higher soil protection than CT through a lower wind erodible fraction of soil surface (on average, 10% less) and a significantly higher percentage of soil cover with crop residues and clods (30% higher). Random roughness was also higher after RT than after CT (15 vs. 4%). These results indicate that RT can be an effective soil management practice for wind erosion prevention during the fallow period in semiarid Aragón. The study shows, likewise, that significant changes in soil aggregate size distribution associated with wind erosion processes may occur in short periods of time. Thus, temporal variability of soil surface properties, including crust and clods stability, needs to be considered in wind erosion research in agricultural soils.     

Assessing non-chemical weeding strategies through mechanistic modelling of blackgrass (Alopecurus myosuroides Huds.) dynamics

Because of environmental and health safety issues, it is necessary to develop strategies that do not rely on herbicides to manage weeds. Introducing temporary grassland into annual crop rotations and mechanical weeding are the two main features that are frequently used in integrated and organic cropping systems for this purpose. To evaluate the contribution of these two factors in interaction with other cropping system components and environmental conditions, the present study updated an existing biophysical model (i.e. AlomySys) that quantifies the effects of cropping system on weed dynamics. Based on previous experiments, new sub-models were built to describe the effects on plant survival and growth reduction of mechanical weeding resulting from weed seedling uprooting and covering by soil, and those of grassland mowing resulting from tiller destruction. Additional modifications described the effect of the multi-year crop canopy of grassland on weed survival, growth, development and seed return to the soil. The improved model was used to evaluate the weed dynamics over 27 years in the conventional herbicide-based cropping system most frequently observed in farm surveys (i.e. oilseed rape/winter wheat/winter barley rotation with superficial tillage) and then to test prospective non-chemical scenarios. Preliminary simulations tested a large range of mechanical weeding and mowing strategies, varying operation frequencies, dates and, in the case of mechanical weeding, characteristics (i.e. tool, working depth, tractor speed). For mechanical weeding soon after sowing, harrowing was better than hoeing for controlling weed seed production. The later the operation, the more efficient the hoeing and the less efficient the harrowing. Tractor speed had little influence. Increasing tilling depth increased plant mortality but increased weed seed production because of additional seed germination triggering by the weeding tool. Decreasing the interrow width for hoeing was nefarious for weed control. The best combinations were triple hoeing in oilseed rape and sextuple harrowing in cereals. The best mowing strategy was mowing thrice, every 4–6 weeks, starting in mid-May. The best individual options were combined, simulated over 27 years and compared to the herbicide-based reference system. If herbicide applications were replaced solely by mechanical weeding, blackgrass infestation could not be satisfactorily controlled. If a three-year lucerne was introduced into the rotation, weed infestations were divided by ten. Replacing chisel by mouldboard ploughing before winter wheat reduced weed infestations at short, medium and long term to a level comparable to the herbicide-based reference system.     

Effects of tractor weight,wheel placement and depth of ploughing on the infestation of perennial weeds in organically farmed cereals

To ensure optimum conditions for organic cereal growing, it is important to minimize both compaction and soil inversion depth. The relative effects of using light versus heavier tractors, shallow versus deeper ploughing and on-land versus in-furrow wheel placement during ploughing were investigated in three-year organic rotations dominated by cereals with naturally infested stands of perennial weeds. The second part of the experiments was carried out in continuous barley with transplanted root fragments of Cirsium arvense (L.) Scop. and rhizome pieces of Elymus repens (L.) Gould. Ploughing was performed in spring under favourable weather conditions. Neither tractor weight nor wheel placement influenced decisively the numbers and above-ground biomass of perennial weeds. Depth of ploughing, on the other hand, affected both perennial weed infestation and yield levels consistently. Weed numbers and the total above-ground weed biomass were mostly 50% lower with deep ploughing (25 cm) than with shallow ploughing (15 cm). The greatest advantage of deep ploughing appeared in the control of C. arvense, which in some cases was reduced by more than 90% compared to shallow ploughing. In organic rotations dominated by cereals, therefore, combating of perennial weeds by deep ploughing may be more important than factors such as tractor weight and wheel placement.     

Effects of Reduced Tillage and Fertilization Practices on Soil Characteristics, Plant Water Status, Growth and Yield of Upland Cotton

Three different tillage practices, conventional (mouldboard ploughing at 22–25 cm plus one rotary hoeing at 5–6 cm, CT), minimum (one rotary hoeing at 12–15 cm, MT), and no‐tillage (direct drilling in soil covered by vetch residues, NT), combined with three fertilization treatments, inorganic (50 kg N ha^?1 as ammonium sulphate), cattle manuring (30 t ha^?1), and control (no‐fertilizer), were applied on a cotton crop (Gossypium hirsutum L. cv. Acala SJ‐2) grown on a clay loam soil in the field of the Agricultural University of Athens. Soil (gravimetric water content, bulk density, and penetration resistance in the top 40 cm) and plant parameters (root growth, leaf water potential, leaf area growth and seedcotton yield) were recorded throughout the cultivation period in all treatments. No‐tillage was associated with significantly higher values of soil water throughout the observation period caused by the vetch mulch. Bulk density and penetration resistance were initially higher in the no‐tilled plots, but they became significantly lower after 2–3 months from sowing. These beneficial effects on soil properties favoured root growth, expressed as root surface density, in the NT‐plots at the top soil layer. Similar, although less spectacular, effects were observed in the manured plots. Plant water status, expressed in terms of the water potential index, was significantly and consistently best in the NT‐ and worst in the CT‐plots throughout crop growth. In addition, NT favoured a better foliage growth and resulted in significantly higher yields than the other tillage practices. In general, NT, and in second instance, MT considerably improved plant water status, and hence foliage growth and yield in comparison with CT by maintaining higher levels of soil water and improving root growth. Manuring positively interacted with the reduced tillage practices for most soil and plant parameters.     

Responses of soil properties,root growth and crop yield to tillage and crop residue management in a wheat–maize cropping system on the North China Plain

Crop residue removal and subsoil compaction are limiting to yield improvement in the North China Plain (NCP). We conducted a field study composed of six consecutive crop growing seasons from 2010 to 2013 in Henan province, China, to determine responses of soil properties, crop root distribution and crop yield to tillage and residue management in a wheat–maize cropping system under irrigated conditions. Tillage practices comprised mouldboard ploughing (MP) to a depth of 15-cm, deep mouldboard ploughing (DMP) to a depth of 30-cm, and chisel ploughing (CP) to a depth of 30-cm. Crop residue management included crop residue retained (CRRet) and crop residue removed (CRRem). The results indicated that yields in DMP and CP increased by 6.0% and 7.3% for wheat and by 8.7% and 9.0% for maize, respectively, relative to MP. The CRRet treatment also increased wheat yield by 6.7% and maize yield by 5.0%. The yield increases under DMP and CP were related to reduced bulk density and soil penetration resistance, increased soil water content, improved total N distribution and improved root density (0–60-cm). Compared with MP, the root mass density under DMP and CP were increased by 43.4% and 42.0% for wheat and by 40.6% and 39.4% for maize, respectively. The yield increases under CRRet were also related to increased soil water content, reduced penetration resistance and increased N status (0–40-cm). Overall, for DMP + CRRet and CP + CRRet, a more favorable soil environment alongside greater root mass density and suitable spatial distribution resulted in higher grain yields of wheat and maize. Thus, compared with conventional shallow tillage practice, DMP or CP with residue application could improve soil quality and agricultural productivity under irrigated areas with loam soil in the NCP.     

Vorfruchtwirkurigen unterschiedlicher Rotationsbrachen auf Winterweizen

Effects of rotational fallows (‘set-aside land’) on subsequent winter wheat. The aim of the present study was to investigate the effects of different fallow treatment on subsequent winter wheat. The field trials included rotational fallows planted with Trifolium repens, Festuca rubra and Lolium perenne sown under winter barley compared to complete fallow and natural fallow without seed application and fallows planted with Trifolium pratense, Festuca rubra and Dactylis glomerata sown under winter wheat. After ploughing up the fallow vegetation, winter wheat was planted for 2 succeeding years at two levels of N-fertilization. Herbicides and fungicides were not applied. The following criteria were investigated: biomass-production, N-uptake, yield, weed infestation, nitrate and water content of the soil. In autumn, after ploughing up the fallow vegetation, the nitrate content of the soil (0—150 cm) increased by up to 210 kg NO₃-N/ha after complete fallow, by up to 60 kg NO₃-N/ha after natural fallow and by up to 75 and 130 kg NO₃-N/ha after fallows cropped with Trifolium repens and Trifolium pratense, respectively. Low nitrate levels of 20—27 kg NO₃-N/ha were observed after fallows planted with grass. N-immobilization caused by ploughing up grass fallows continued until the first harvest of the subsequent winter wheat. In the second year of winter-wheat, no differences of N-mineralization dependent on the previous fallow crop occurred, except in the case complete fallow which showed lower N-mineralization. It can be concluded that fallows cropped with grass lead to a higher nitrogen fertilizer requirement m the succeeding crops. Festuca rubra was able to form dense swards in strong competition with weeds and to decrease the abundance of Alopecurus myosuroides and Apera spíca-venti in subsequent winter wheat, while natural fallow and fallow planted with Trifolium repens and Lolium perenne caused epidemical increases in grass-weed density. Preceding crop effects on grain yield of the winter wheat showed a close relation to N-supply and were compensated by mineral N-fertilization. After natural fallow and fallow covered with Trifolinm repens, yield reductions due to grass-weed competition occurred. Undersown Festuca rubra seems to possess a special suitabihty for cultivation in routional fallows. It establishes itself strongly under different cover crops and is able to form dense swards in strong competition with weeds. Grass-weed density in the succeeding crops will be reduced and nitrate leaching will still be prevented after ploughing up the fallow vegetation. N-fertilization of the subsequent crops must be carried out under considerations of higher N-requirements which is probably not entirely due to a stronger N-immobilization.     

Winter barley performance under different cropping and tillage systems in semiarid Aragon (NE Spain)

Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5–6-month fallow) and a crop–fallow rotation (BF) (16–18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999–2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day⁻¹) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration (T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable.     

A methodology for multi-objective cropping system design based on simulations. Application to weed management

Weeds are harmful for crop production but important for biodiversity. In order to design cropping systems that reconcile crop production and biodiversity, we need tools and methods to help farmers to deal with this issue. Here, we developed a novel method for multi-objective cropping system design aimed at scientists and technical institutes, combining a cropping system database, decision trees, the “virtual field” model FlorSys and indicators translating simulated weed floras into scores in terms of weed harmfulness (e.g. crop yield loss, weed-borne parasite risk, field infestation), weed-mediated biodiversity (e.g. food offer for bees) and herbicide use intensity. 255 existing cropping systems were simulated with FlorSys, individual indicator values were aggregated into a multi-performance score, and decision trees were built to identify combinations of management practices and probabilities for reaching performance goals. These trees are used to identify the characteristics of existing cropping systems that must be changed to achieve the chosen performance goals, depending on the user's risk strategy. Alternative systems are built and simulated with FlorSys to evaluate their multi-criteria performance. The method was applied to an existing oilseed rape/wheat/barley rotation with yearly mouldboard ploughing from Burgundy which was improved to reconcile weed harmfulness control, reduced herbicide use and biodiversity promotion, based on a risk-minimizing strategy. The best alternative replaced a herbicide entering plants via shoot tips (during emergence) and roots after barley sowing by a spring herbicide entering via leaves, introduced crop residue shredding before cereals and rolled the soil at sowing, which reduced the risk of unacceptable performance from 90% to 40%. When attempting to reconcile harmfulness control and reduced herbicide use, the best alternative changed the rotation to oilseed rape/wheat/spring pea/wheat, replaced one herbicide in oilseed rape by mechanical weeding, delayed tillage before rape and applied the PRE herbicide before oilseed rape closer to sowing. This option reduced the risk of unacceptable performance to 30%. None of the initial or alternative cropping systems succeeded in optimal performance, indicating that more diverse cropping systems with innovative management techniques and innovative combinations of techniques are needed to build the decision trees. This approach can be used in workshops with extension services and farmers in order to design cropping systems. Compared to expert-based design, it has the advantage to go beyond well-known options (e.g. plough before risky crops) to identify unconventional options, with a particular focus on interactions between cultural techniques.     

Crop sequence,crop protection and fertility management effects on weed cover in an organic/conventional farm management trial

A survey of 128 plots, in 2008, of a trial where the effects of crop protection can be separated from those of fertility management, generated weed cover data within six crops (winter wheat, winter barley, spring barley, potatoes, cabbages and a grass/clover ley). The effects of the 2008 crop types, of the two preceding crops and of organic and conventional crop protection and fertility management, were assessed using mixed-effects models and constrained ordination. Cover data for 22 weed species and for monocotyledon, dicotyledon, annual, perennial and total weed cover were used. Cover of 15 weed species, and of the five weed groups, was significantly affected by 2008 crops, with cover highest in spring beans and cabbage. Nine and four weed species 2008 cover were significantly related to crops grown in 2007 and 2006 respectively, as were dicotyledon, annual and total weed cover, but not monocotyledon or perennial cover. Cover of 15 species, and the five groups, was significantly higher in plots with organic crop protection, but only eight species and annuals were significantly affected by fertility management. Crop:crop protection produced the most significant interactions with most cover in organically managed plots. Five species, perennials and total weed cover produced significant three-factor models. The greatest weed cover was in organic crop protected but conventionally fertilised spring barley and the least in totally conventional winter barley. Other factors such as crop density and mechanical weeding also affected 2008 weed cover. The ordination indicated that most of the 22 species were strongly associated with crops from all three years. The sequence of crops in the rotation had a profound effect on weed cover. Where three spring-sown, difficult to weed, crops were grown in sequence (spring beans, potatoes and vegetables, spring barley) weed cover increased. However, cover was limited in grass/clover and some cereal plots with different preceding crops. Models predicting weed cover may need to take into account crop sequences within crop rotations, as well as the more usual management inputs.     

Effect of Three Tillage Systems on Weed Flora in a 3-Year Rotation with Four Crops

Field experiments were conducted to determine the effect of tillage on the dry weight, frequency (PF), density (PD) and species composition of the weed population. Three tillage systems (CT: conventional tillage, MT: minimum tillage and NT: no tillage) were compared in a 3-year rotation [wheat–vetch (green manure)–cotton–barley]. Decreases in PF, mean PD and number of species were observed under NT because in this system the soil remains undisturbed, and conditions are not suitable for seed germination. In contrast, annual weeds had a higher PF under the CT system, because they mainly propagate by seed and soil tillage creates more favourable growth conditions; thus they also had a higher PD. The highest PF and PD were found for the species Sinapis arvensis and Solanum nigrum . Perennial weeds had higher PD under the NT system, because their roots cannot be destroyed by soil tillage. The number of species was not altered in CT and MT, but was decreased in NT. In winter crops, annual species under CT and MT, and perennial species under NT were observed. In cotton crops, perennial species under CT and MT, and annual species under NT were observed. The mean PD of weed species in the first crop followed the sequence NT > MT > CT and in subsequent crops followed the reverse sequence CT > MT > NT.     

洞庭湖区播种期、耕作方式和施肥对大麦农艺性状的影响

为了推进湖南饲用大麦(Hordeum vulgare L.)的种植,对冬闲稻田进行有效开发,探索环洞庭湖区大麦栽培抗倒高产节本的栽培措施。本研究使用裂裂区设计的田间试验方法调查不同播种期、不同耕作方式和施肥对大麦产量构成因子如有效穗数、穗粒数和千粒重等的影响。结果表明：洞庭湖区冬闲田种植大麦,不同播种期、耕作方式和施肥对大麦的农艺性状和产量有显著的影响(P<0.05)。在不影响双季稻生产的情况下,播种期最好不要超过11月4日,且翻耕可以显著提高大麦产量(P<0.05),而施肥对大麦产量影响较小,可以考虑不施肥。总体来看,‘华大麦4号’的小区种子产量最高达到9.5 kg每小区,适合洞庭湖区种植并可进行进一步栽培研究。     

ROTOR,a tool for generating and evaluating crop rotations for organic farming systems

As with conventional farming, the improvement of organic farming systems requires agronomic planning tools to enhance economic performance. Crop rotation planning plays a crucial role in organic arable farming systems due to the renunciation of mineral nitrogen fertilisers and pesticides. Our objective was to develop a tool for generating and evaluating site-specific and agronomically sustainable crop rotations for organic farming systems in central Europe. The resulting static rule-based model, called ROTOR, consists of two basic steps: (A) A set of annual crop production activities (CPAs) is assembled semi-automatically from single site and crop-specific field operations using a relational data base. The database includes all relevant crops recorded separately with inputs and outputs, machinery and timing. Starting from stubble tillage and ending with the last harvest measure, the CPAs describe the current best cropping practices. Different CPAs are included for each crop according to (i) the type of crop preceding and (ii) the field operations following: whether ploughing or non-inverting tillage, undersowing crops, using catch crops, manuring, straw harvesting, or mechanical weed control. The former allows for the modelling of all possible positions of a crop within a crop rotation and the consequential effects of preceding crops. The CPAs are evaluated using rule-based assessment modules for yield, economic performance, N balance, nitrate leaching, and weed infestation risks. These modules have been developed using data from field experiments, farm trials and surveys, expert knowledge and a soil–crop simulation model. (B) Within the crop generation module, all possible sequences of CPAs are linked to 3–8-year preliminary crop rotations. Agronomically sustainable crop rotations are selected according to exclusion criteria (i.e., thresholds for N balance, weed infestation risks, phytosanitary and chronological restrictions) and ranked, e.g. by economic performance. The model was tested by comparing (i) estimated with observed yields and (ii) generated with existing rotations. These comparisons, based on data obtained from two farm surveys from North Eastern Germany, indicate the validity and usability of the model approach. ROTOR was found to support the complex crop rotation planning in organic farming systems requiring rotations with overlapping undersown main and cover crops. ROTOR is able to reduce the risk of planning failures by offering a quantitative method of optimisation of weed and site-specific N management.     

Influence Of Tillage On Soil Aeration

Air- porosity of soil can be altered by tillage. Therefore, it plays a significant role in protecting plants against deficient aeration during critical periods of their life cycle. The effect of five tillage treatments (mouldboard, cultivator, rotary tiller, wedge and zero tillage) and three mulch treatments (paddy straw, rice husk and bare) on the soil oxygen diffusion rate (ODR) during the various growth phases of peanut crop ( Arachis Hypogaea L.) were investigated on a lateritic sandy loam soil (utilsol). These experiments were conducted for two consecutive seasons. ODR values were higher in tilled plots. Among tillage treatments, the highest ODR was recorded under mouldboard (60.51 × 10^-8 g cm^-2 min^-1), followed closely by cultivator (57.65 × 10^-8g cm^-2 min^-1), and it was lowest under rotary tiller (46.29 × 10^-8 g cm^-2 min^-1). During the later growth stages and also in lower soil depths, the differences between the values of ODR narrowed down. Among mulch treatments, plots with rice husk (53.98 × 10^-8 g cm^-2 min^-1), had the higher ODR values. Bulk density was lower, whereas total and aeration porosity were higher, under mouldboard and cultivator. Soil temperatures were also higher under mouldboard and cultivator tilled plots.     

Evaluation of monocropped and intercropped grain legumes for cover cropping in no-tillage and reduced tillage organic agriculture

Intensive tillage by means of mouldboard ploughing can be highly effective for weed control in organic farming, but it also carries an elevated risk for rapid humus decomposition and soil erosion. To develop organic systems that are less dependent on tillage, a two-year study at Reinhardtsgrimma and Köllitsch, Germany was conducted to determine whether certain legume cover crops could be equally successfully grown in a no-till compared with a reduced tillage system. The summer annual legumes faba bean (Vicia faba L.), normal leafed field pea (Pisum sativum L.), narrow-leafed lupin (Lupinus angustifolius L.), grass pea (Lathyrus sativus L.), and common vetch (Vicia sativa L.) were examined with and without sunflower (Helianthus annuus L.) as a companion crop for biomass and nitrogen accumulation, symbiotic nitrogen fixation (N₂ fixation) and weed suppression. Total cover crop biomass, shoot N accumulation and N₂ fixation differed with year, location, tillage system and species due to variations in weather, inorganic soil N resources and weed competition. Biomass production reached up to 1.65 and 2.19 Mg ha⁻¹ (both intercropped field peas), and N₂ fixation up to 53.7 and 60.5 kg ha⁻¹ (both common vetches) in the no-till and reduced tillage system, respectively. In the no-till system consistently low sunflower performance compared with the legumes prevented significant intercropping effects. Under central European conditions no-till cover cropping appears to be practicable if weed density is low at seeding. The interactions between year, location, tillage system and species demonstrate the difficulties in cover crop species selection for organic conservation tillage systems.     

Estimation of Soil Evaporation During Fallow Seasons to Assess Water Balances for No‐Tillage Crop Rotations

Abstract Estimates of soil evaporation and available soil water of no‐tillage fields under farm conditions are important to assess soil water status at sowing of rainfed grain crops. The objective of this study was to predict stored soil water of no‐tillage fields during the fallow periods following soybean (Glycine max (L.) Merr.) and maize (Zea mays L.) crops by accounting for decreased soil evaporation as a result of the residues left on the soil surface. Three simple phenomenological models were used to simulate stored soil water under field conditions at seven locations in Argentina. Two models calculated decreased soil evaporation based on crop residue mass, and the third assumed a constant fractional decrease in bare soil evaporation. All models gave good estimates of soil water content during the fallow periods following a soybean crop. In cases with large quantities of maize residue, however, the models resulted in more water retention in the soil than observed as a consequence of underprediction of soil evaporation. These results indicate that full benefit of crop residue was not being achieved in these fields, probably due to a failure to finely chop and uniformly distribute the crop material on the soil surface.     

Chemical Properties of Eroded Soil Material

In a 5‐year stationary investigation at an experimental station in central Croatia, total amounts of erosional drift were measured on a Stagnic Luvisol on which six tillage methods were used. The chemical properties of the tilled soil and the erosional drift were recorded for each trial method in the same plots. A generally higher soil reaction value, higher organic matter content and larger amounts of available phosphorus and potassium were found in the majority of erosional drifts compared to plot soil. On black fallow, erosional drifts contained significantly larger amounts of organic matter, available phosphorus and potassium than in other treatments. Higher contents of organic matter, phosphorus and potassium were recorded in erosional drifts from spring crop cultivation than in those from cultivation of winter wheat, oil‐seed rape and a consociation of summer barley and soybean. Also, higher losses of organic matter, phosphorus and potassium by erosional drift were recorded for the up/down the slope tillage methods than for no‐tillage and tillage across the slope. This suggests that no‐tillage and tillage across the slope can be recommended for this region, since these tillage methods conserve the soil and substantially reduce water pollution by chemical agents applied in agricultural production.     

Growth and yield of spring cereals during transition to zero tillage on clay soils

Due to the high cost of fuel and labour associated with conventional tillage, and because of their advantageous environmental consequences, interest in reduced and zero tillage systems has increased. Direct drilling into zero tilled (ZT) soil of two spring barley (Hordeum vulgare L.) cultivars (six-rowed Rolfi and two-rowed Saana), spring oats (Avena sativa L., cultivar Roope), and spring wheat (Triticum aestivum L., cultivar Kruunu) was compared with conventional tillage (CT) and drilling into ploughed soil. Two field experiments were conducted on clay soils (clay content > 50%) between latitudes 60° and 61° N. Seed and fertilizer were placed in the same row in ZT and in separate rows in CT. Oats was the most productive spring cereal species in ZT. Establishment of spring wheat was often poor. Barley was most vulnerable to water surplus during early growth and drought during late growth. High levels of crop residues caused problems in soil drying in spring and growth of monocultures of oats and wheat. A higher seeding rate was advantageous in zero tilled clay soil. The substantial grain yield decrease suggests need for improving ZT.Long-term trials are required to determine whether ZT suits clay soils as soil structure can change over time and weather conditions play a major role in the productivity of differently tilled soils.     

Straw management, crop rotation, and nitrogen source effect on wheat grain yield and nitrogen use efficiency

Nitrogen fertilizer management from different sources and annual crop rotations are important components of wheat (Triticum aestivum L.) production systems, especially where air and soil quality issues have prompted a search for alternatives to wheat straw burning. This study examined the effects of two different wheat straw management options (burning and incorporation by tillage), three crop rotations [wheat-sesbania (Sesbania spp.), wheat–maize (Zea mays L.), and wheat-clean fallow] and three N sources (urea, chicken manure, and urea plus chicken manure) on wheat grain yield and N use efficiency. The experiment was conducted as split–split plot treatment arrangement with three replications for eight wheat cropping seasons in the state of Sonora, Mexico. Results indicated that both wheat grain yield and N use efficiency were higher with burning than incorporation of wheat straw and with fertilization with urea or urea plus chicken manure than chicken manure alone. As shown by the crop rotation-by-straw management interaction, planting sesbania following incorporation of the straw by tillage produced comparable grain yields to straw burning treatment. In contrast, wheat in annual rotation with maize produced the lowest wheat grain yield and N use efficiency irrespective of the wheat straw management and N source applied.