Winter Crop Rotation Research Articles

Burial and subsequent growth of rigid ryegrass (Lolium rigidum) and ripgut brome (Bromus diandrus) following strategic deep tillage

AbstractSoil amelioration via strategic deep tillage is occasionally utilized within conservation tillage systems to alleviate soil constraints, but its impact on weed seed burial and subsequent growth within the agronomic system is poorly understood. This study assessed the effects of different strategic deep-tillage practices, including soil loosening (deep ripping), soil mixing (rotary spading), or soil inversion (moldboard plow), on weed seed burial and subsequent weed growth, compared with a no-till control. The tillage practices were applied in 2019 at Yerecoin and Darkan, WA, and data on weed seed burial and growth were collected during the following 3-yr winter crop rotation (2019 to 2021). Soil inversion buried 89% of rigid ryegrass (Lolium rigidum Gaudin) and ripgut brome (Bromus diandrus Roth) seeds to a depth of 10 to 20 cm at both sites, while soil loosening and mixing left between 31% and 91% of the seeds in the top 0 to 10 cm of soil, with broad variation between sites. Few seeds were buried beyond 20 cm despite tillage working depths exceeding 30 cm at both sites. Soil inversion reduced the density of L. rigidum to <1 plant m−2 for 3 yr after strategic tillage. Bromus diandrus density was initially reduced to 0 to 1 plant m−2 by soil inversion, but increased to 4 plants m−2 at Yerecoin in 2020 and 147 plants at Darkan in 2021. Soil loosening or mixing did not consistently decrease weed density. The field data were used to parameterize a model that predicted weed density following strategic tillage with greater accuracy for soil inversion than for loosening or mixing. The findings provide important insights into the effects of strategic deep tillage on weed management in conservational agricultural systems and demonstrate the potential of models for optimizing weed management strategies.

CROP ROTATIONAL EFFECTS ON INFESTATION OF STEM BORERS IN RICE

The present study investigates the impact of crop rotation on the infestation of stem borers in rice crops. This research was carried out in the field at Shaheed Zulfiqar Ali Bhutto Agricultural College Dokri, Sindh, Pakistan. Several rotation practices were tested, including Rice fallow Rice, Rice-Wheat-Rice, Rice-Gram-Rice, Rice-Barseem-Rice, and Rice-Mustard-Rice. The results of the study revealed interesting findings. The lowest infestation rate, approximately 1.92% of rice stem borers, was observed in the Rice-Barseem-Rice rotation. This was followed by Rice-Mustard-Rice at 2.18%, Rice-Gram-Rice at 2.40% and Rice-Wheat-Rice at 3.21%. In contrast, the highest infestation rate, reaching 4.99%, was recorded in the Rice-fallow-Rice rotation system. These findings suggest that incorporating winter rotation crops such as Mustard, Barseem, and Gram into the cropping system can significantly reduce the population density of rice stem borers. On the contrary, mono-cropping, as exemplified by the Rice-fallow-Rice rotation, appears to favor stem borer infestations. In light of these results, it is recommended that further research and understanding be developed to implement cultural control methods and ensure ecological safety within winter crop rotation systems. This study underscores the importance of diversified crop rotation practices in mitigating the infestation of harmful pests like rice stem borers, contributing to sustainable agriculture and higher crop yields.

Opportunities and Challenges for Cover Cropping in Sustainable Agriculture Systems in Southern Australia

Southern Australian farming systems operate predominantly under Mediterranean climatic conditions, which limit the choice of cover crops suitable for enhancement of ground cover and soil moisture retention, erosion control, atmospheric soil nitrogen (N) fixation, and weed suppression between cash crop rotations. Given that the successful establishment of cover crops is climate-driven and also influenced by edaphic factors such as soil pH and salinity, there has been increased interest by southern Australian producers in identifying potential cover crop species well adapted to specific Australian farming systems, which provide vital ecosystem services and sustainable economic benefits through the improvement of soil properties. This review summarises recent findings on cover crop inclusion in diverse farming systems in southern Australia, including continuous and mixed broadacre cropping as well as viticulture and horticulture systems, to identify opportunities and limitations related to their use. Cover crop inclusion in viticulture and pasture systems with lower moisture stress was observed to benefit the subsequent cash crop through enhanced production potential. Long-term, multi-site field experimentation incorporating summer cover crops in winter crop rotations showed that cover crops enhanced ground cover and soil water infiltration in some locations across southern Australia while sometimes increasing winter crop yield, suggesting that soil type and regional climatic conditions greatly influenced the delivery of multiple cover crop benefits. Collectively, these studies have suggested a need for longer-term field evaluations using multiple cover crop species and investigations of termination options under varying environmental and soil conditions to better quantify the legacy effects of cover crops.

Decomposition of yield gap of soybean in environment × genetics × management in Southern Brazil

Estimates and explanations of yield gaps make it possible to increase crop production through improvements in agricultural systems and better crop management. The combination of field data and crop modeling allows scaling the efforts needed to close the yield gap. The objective of this study was to decompose the soybean yield gap into its constituents and to quantify the influence of the main limiting factors on soybean yield in Rio Grande do Sul, Brazil. Yield potentials and water-limited yield potentials were estimated by the CSM-CROPGRO soybean simulation model to quantify the yield gaps related to the choice of cultivar and sowing time, water gap, and gap related to other management practices. We used data from a survey of 853 fields reported by farmers over four growing seasons to quantify yield gaps for each field and the influence of management practices on soybean yields. The annual increase in soybean yield in RS depends on improvements in management (44 %), genetic breeding (42 %) and climate changes (14 %). We identified a gap of 995 kg ha−1 attributed to the choice of cultivar and sowing date, 2006 kg ha−1 attributed to water availability during the developmental cycle and 1437 kg ha−1 attributed to management improvements. A yield gap of 2432 kg ha−1 (genotype × environment gap and management gap) can be closed with adjustments in management practices such as choosing the best cultivar, sowing date, soil pH, P2O5 and K2O fertilization, no-tillage, and summer and winter crop rotation.

Reniform Nematode Management Using Winter Crop Rotation and Residue Incorporation Methods in Greenhouse Experiments.

Rotylenchulus reniformis (reniform nematode, RN) is an important pathogen in cotton production. Cultural practices such as crop rotation and biofumigation-management of soil pathogens by biocidal compounds from crop residues-may help manage RN. The objective of this study was to evaluate the efficacy of winter crops for RN management through combinations of rotation and crop residue incorporation in a cotton greenhouse experiment. A total of 10 treatments were evaluated in soil inoculated with RN: three winter crops (carinata, oat, or hairy vetch) grown in rotation with no shoot organic matter (OM) incorporated (1-3), fresh shoot OM incorporated (4-6), or dry shoot OM incorporated (7-9), and a fallow control (10). Roots were re-incorporated in all treatments except fallow. Subsequently, cotton was grown. Oat and fallow were better rotation crops to lower soil RN abundances at winter crop termination than hairy vetch and carinata. After the OM incorporation treatments and cotton growth, oat was generally more effective at managing RN in cotton than carinata or hairy vetch. Within each crop, incorporation treatment generally did not affect RN management. Cotton growth was not consistently affected by the treatments.

Winter crop rotation intensification to increase rice yield, soil carbon, and microbial diversity

Crop rotation has widely contributed to increasing farmland biodiversity as well as to improving soil carbon pools and microbial diversity. However, there is a weak understanding of the suitability of winter crop rotation intensification in double rice fields, especially rotation with various winter crops. For this task, a long-term field experiment based on one from 2012 was conducted with five winter crop systems for double rice: winter fallow (T0), winter milk vetch (T1), winter rape (T2), winter garlic (T3), winter rotation intensification with potato, milk vetch, and rape (T4). Parameters such as crop yield, soil carbon, nitrogen, and soil microorganism were measured. It was found that compared to winter fallow, winter milk vetch, rape, garlic, and crop rotation intensification practices increased the late rice yield by 2.5%, 2.3%, 4.5%, and 3.7%, respectively; winter garlic and crop rotation intensification also increased the early rice yield by 4.6% and 3.5%, respectively. This is associated with the promotion of rice tillering. At the same time, for winter crop rotation, compared to winter fallow, the soil organic carbon increased by 21%. With the input of diversified crop residues, winter crops were effective in soil carbon sequestration, improving soil microbial structure, and increasing soil microbial diversity. The Shannon diversity index of winter crops ranged from 9.75 to 9.91, while winter fallow was 9.38. The Simpson’s diversity index of winter crops ranged from 0.997 to 0.998, while winter fallow was 0.996. In conclusion, winter crop practices, especially winter crop rotation intensification, can enhance soil health and sustainability in double rice fields through its positive feedback on crop yield, soil carbon sequestration, and microorganisms.

Higher economic benefits and changes in soil fertility due to intensifying winter crop rotation in double-rice cropping systems

Farmers are increasingly planting vegetables during the winter fallow period in the double-rice growing area of Guangdong Province, southern China. The intensified winter crop rotation system (rice-rice-vegetable, RRV) may improve the annual planting benefit and change the soil fertility. To address this, yields, biomass, and profitability of each crop in the RRV, relative to the traditional rice-rice-fallow system (RRF), were compared, and the dynamics of physical, chemical and biological properties of soil at different crop stages were determined in this paper. The annual crop yield, biomass and economic return of RRV were significantly higher than those of RRF due to the inclusion of winter vegetables (green beans) in the cropping system. The contribution of green beans to the total revenue per year for RRV was as high as 73%. Filling winter fallow with green beans had no influence on the yield of early and late rice. Soil NO3−-N, available P, exchangeable K, exchangeable Fe, exchangeable Cu and acid phosphatase activity at the winter stage were significantly higher in RRV than in RRF, whereas soil pH, soil organic carbon (SOC), dissolved organic carbon (DOC), exchangeable Ca, exchangeable Mg, catalase activity, dehydrogenase activity and invertase activity at the winter stage were lower. The soil NO3−-N, exchangeable Fe, exchangeable Cu, and acid phosphatase activity during the early rice stage also tended to be higher in the RRV system. The annual dynamics of soil physical, chemical and biological properties were proven to be greater in the RRV system than in the RRF system. The findings of our study contribute to the understanding of dynamic changes in physical, chemical and biological properties of soil across different crop stages due to intensified green bean planting during the winter fallow period in a double-rice cropping system, which will be useful for the sustainable development of RRV.

Relative success of frost-resistant variants of Avena fatua: a field experiment

AbstractWhile climate change mainly applies to global warming and subsequent drought periods, freezing periods also are changing and may trigger genetic adaptation. However, there are few prospective, experimental demonstrations. This paper investigates how effectively genetic frost-resistant variants can respond differently to frost periods, especially in farmers’ fields where various other selection pressures occur. An experiment using Avena fatua variants was set up in the field over 8 years of winter crop rotation. The frequency of each variant identified by their leaf isozymes was estimated every year. Six years were necessary to observe a weak trend towards an increased frequency of the frost-resistant phenotype, while the other variants had apparent erratic behaviour. Selection of the frost-resistant variant was challenged by irregular low temperature selection pressure, differential dormancy, germination and seed production, and possibly herbicide sensitivity that mitigated the expression of the selection response. This experiment shows how plant polymorphism and farmers’ practices that superimpose habitat unpredictability diversify possible responses to selection pressures and delay adaptation. However, if climate change brings both higher mean temperatures and extreme values, changes of apparent plant phenology could happen for weeds species displaying the appropriate genetic variability within the time-frame of farmers’ career, thus necessitating correlative adaptation of farming practices.

Effect of various crop rotations on rice yield and nitrogen use efficiency in paddy–upland systems in southeastern China

To evaluate the effects of various rotation systems on rice grain yield and N use efficiency, a paddy–upland cropping experiment (2013–2016) was conducted in southeastern China. The experiment was designed using six different rice––winter crop rotations: rice–fallow (RF), rice–wheat (RW), rice–potato with rice straw mulch (RP), rice–green manure (Chinese milk vetch; RC–G), rice–oilseed rape (RO), and rice–green manure crop (oilseed rape with fresh straw incorporated into soil at flowering; RO–G) and three N rates, N0 (0 kg N ha−1), N1 (142.5 kg N ha−1), and N2 (202.5 kg N ha−1). Average rice yields in the RF (5.93 t ha−1) rotation were significantly lower than those in the rotations with winter crops (7.20–7.48 t ha−1) under the N0 treatment, suggesting that incorporation of straw might be more effective for increasing soil N than winter fallow. The rice yield differences among the rotations varied by year with the N input. In general, the grain yields in the RP and RO–G rotations –were respectively 11.6–28.5% and 14.80–37.19% higher than those in the RF in plots with N applied. Increasing the N rate may have tended to minimize the average yield gap between the RF and the other rotations; the yield gaps were 18.55%, 4.14%, and 0.23% in N0, N1, and N2, respectively. However, the N recovery efficiency in the RF was significantly lower than that in other rotations, except for 2015 under both N1 and N2 rates, a finding that implies a large amount of chemical N loss. No significant differences in nitrogen agronomic efficiency (NAE) and physiological efficiency (NPE) were found between the rotations with legume (RC–G) and non–legume (RO and RW) winter crops, a result that may be due partly to straw incorporation. For this reason, we concluded that the return of straw could reduce differences in N use efficiency between rotations with and without legume crops. The degree of synchrony between the crop N demand and the N supply was evaluated by comparison of nitrogen balance degree (NBD) values. The NBD values in the RP and RW were significantly lower than those in the other rotations under both N1 and N2 rates. Thus, in view of the higher grain yield in the RP compared to the RW under the N1 rate, the RP rotation might be a promising practice with comparable grain yield and greater N use efficiency under reduced N input relative to the other rotations. The primary yield components of the RF and RP were identified as number of panicles m−2 and numbers of kernels panicle−1, respectively. The NAE and NPE were positively correlated with harvest index, possibly providing a useful indicator for evaluating N use efficiency.

Cover crop rotations in no-till system: short-term CO2 emissions and soybean yield

In addition to improving sustainability in cropping systems, the use of a spring and winter crop rotation system may be a viable option for mitigating soil CO2 emissions (ECO2). This study aimed to determine short-term ECO2 as affected by crop rotations and soil management over one soybean cycle in two no-till experiments, and to assess the soybean yields with the lowest ECO2. Two experiments were carried out in fall-winter as follows: i) triticale and sunflower were grown in Typic Rhodudalf (TR), and ii) ruzigrass, grain sorghum, and ruzigrass + grain sorghum were grown in Rhodic Hapludox (RH). In the spring, pearl millet, sunn hemp, and forage sorghum were grown in both experiments. In addition, in TR a fallow treatment was also applied in the spring. Soybean was grown every year in the summer, and ECO2 were recorded during the growing period. The average ECO2 was 0.58 and 0.84 g m2 h–1 with accumulated ECO2 of 5,268 and 7,813 kg ha–1 C-CO2 in TR and RH, respectively. Sunn hemp, when compared to pearl millet, resulted in lower ECO2 by up to 12 % and an increase in soybean yield of 9% in TR. In RH, under the winter crop Ruzigrazz+Sorghum, ECO2 were lower by 17%, although with the same soybean yield. Soil moisture and N content of crop residues are the main drivers of ECO2 and soil clay content seems to play an important role in ECO2 that is worthy of further studies. In conclusion, sunn hemp in crop rotation may be utilized to mitigate ECO2 and improve soybean yield.

Impact of non-target-site-resistance on herbicidal activity of imazamox on black¬grass ( Alopecurus myosuroides Huds.) in comparison to other ALS-graminicides

A black-grass (Alopecurus myosuroides Huds.) resistance-monitoring conducted by BASF in 2010 - 2012 revealed a high number of accessions with resistance against imazamox. However, application of imazamox- based products in a winter crop was limited to winter beans in France and United Kingdom only until the introduction of the Clearfield ® -production system in autumn 2012 in winter oilseed rape. It is therefore assumed that the resistance mechanisms were probably selected by the frequent use of ACCase- and ALS- inhibitors in winter crop rotations during the last 2 decades. Resistance level for each product-biotype combination was calculated according the R-classification system (S, R?, RR, RRR) by directly comparing the product performance on a biotype versus untreated control. Majority of resistant biotypes did not show a target-site mutation at the known codon Pro197 or Trp574. In order to better evaluate the impact of Non- Target-Site-Resistance (NTSR) on the activity of BEYOND (imazamox), ATLANTIS WG (mesosulfuron+iodosulfuron) and ABAK (pyroxsulam), biotypes who have shown an ALS-target-site mutation were removed from further analysis. At the dose rate of 35 g ai/ha BEYOND provided good activity on susceptible biotypes of black-grass almost matching up with ATLANTIS WG and ABAK. However, activity of BEYOND declined stronger on biotypes classified as R? or RR for that product, while ATLANTIS WG and ABAK hardly showed any decline in control on this group of biotypes when applied at the recommended dose rate. It is assumed that the underlying NTSR- mechanism is not effective enough yet to confer resistance to ATLANTIS WG and ABAK, but on BEYOND. In contrast, biotypes classified as R? for ATLANTIS WG did show a stronger impact on the activity of BEYOND and ABAK then of ATLANTIS WG. These differences in control level probably do translate into differences in selection pressure as well.

Soil carbon stratification affected by long-term tillage and cropping systems in southern Brazil

Continuous residue inputs when associated with minimum soil disturbance gradually promote the stratification of soil organic carbon (SOC) in the soil profile. In temperate soils, this characteristic has been used as an indicator of quality of soil management. However, few studies have been conducted with this indicator in tropical and subtropical climates or with the main soil orders in these areas. To fill this gap, this study was carried out in a subtropical climate with two of the major Brazilian soil orders, Oxisol and Alfisol, that together account for 63% of Brazilian agricultural soils. This study tested the hypothesis that the CSR is affected by soil order and climate type. The main treatments were soil tillage and different cropping systems in two long-term experiments carried out in the State of Rio Grande do Sul, Brazil. The first experiment, established in 1985, was conducted over a clayey Hapludox (Oxisol) soil. The main plots were treated with one of two tillage systems (conventional tillage – CT; and no-tillage – NT). The subplots were treated with one of three cropping systems: (a) continuous crop succession (R0) – wheat (Triticum aestivum L.)/soybean (Glycine max L. Merrill); (b) winter crop rotation (R1)–wheat/soybean/black oat (Avena strigosa Schreber)/soybean; (c) summer and winter crop rotation (R2) – wheat/soybean/black oat/soybean/black oat+common vetch (Vicia sativa L. Walp)/maize (Zea mays L.)/forage radish (Raphanus sativus var. oleiferus Metzg.). The second experiment was established in 1991 over a sandy loam distrophic Paleudalf (Alfisol) soil. Five cropping systems were analyzed under no-till: (a) maize+jack beans (Canavalia ensiformis DC)/soybean (M/JB); (b) maize/fallow/soybean (M/F); (c) maize/ryegrass (Lolium multiflorum Lam.)+common vetch/soybean (M/R); (d) maize+velvet beans (Stizolobium cinereum Piper and Tracy)/soybean (M/VB); and (e) maize/radish oil/soybean (M/FR). The carbon stratification ratio (CSR) was assessed in the 19th and 22nd experimental years for Oxisol and in the 10th and 17th years for Alfisol. This index was calculated through the ratio of SOC stocks in the 0–0.05 and 0.05–0.15m soil layers. The CPI was determined through the ratio of SOC stocks in the 0–0.15m soil layer in a given treatment compared with native vegetation. Regardless of the soil order, SOC was influenced by C input and the tillage system; there was a positive linear relationship between CSR and CPI. The relationship between the CSR and the carbon pool index (CPI) was used to infer the quality of soil management. Higher CSR and CPI indices were found under treatments with minimum soil disturbance and intensive crop rotation. Lower CSR and CPI values were associated with frequent mobilization and lower crop diversity. These CSR indices sensitively distinguished the intensity of tillage (NT replacing CT) and cropping systems (cover crops replacing winter fallow or crop succession). The CSR values in subtropical soils investigated were lower than those reported for temperate soils. The soil order affected the critical CSR value being lower in the Oxisol than in the Alfisol. Our findings recommend accept our hypothesis that the CSR is affected by climate and soil order.

Long-term C-CO2 emissions and carbon crop residue mineralization in an oxisol under different tillage and crop rotation systems

Soil C-CO2 emissions are sensitive indicators of management system impacts on soil organic matter (SOM). The main soil C-CO2 sources at the soil-plant interface are the decomposition of crop residues, SOM turnover, and respiration of roots and soil biota. The objectives of this study were to evaluate the impacts of tillage and cropping systems on long-term soil C-CO2 emissions and their relationship with carbon (C) mineralization of crop residues. A long-term experiment was conducted in a Red Oxisol in Cruz Alta, RS, Brazil, with subtropical climate Cfa (Köppen classification), mean annual precipitation of 1,774 mm and mean annual temperature of 19.2 ºC. Treatments consisted of two tillage systems: (a) conventional tillage (CT) and (b) no tillage (NT) in combination with three cropping systems: (a) R0- monoculture system (soybean/wheat), (b) R1- winter crop rotation (soybean/wheat/soybean/black oat), and (c) R2- intensive crop rotation (soybean/ black oat/soybean/black oat + common vetch/maize/oilseed radish/wheat). The soil C-CO2 efflux was measured every 14 days for two years (48 measurements), by trapping the CO2 in an alkaline solution. The soil gravimetric moisture in the 0-0.05 m layer was determined concomitantly with the C-CO2 efflux measurements. The crop residue C mineralization was evaluated with the mesh-bag method, with sampling 14, 28, 56, 84, 112, and 140 days after the beginning of the evaluation period for C measurements. Four C conservation indexes were used to assess the relation between C-CO2 efflux and soil C stock and its compartments. The crop residue C mineralization fit an exponential model in time. For black oat, wheat and maize residues, C mineralization was higher in CT than NT, while for soybean it was similar. Soil moisture was higher in NT than CT, mainly in the second year of evaluation. There was no difference in tillage systems for annual average C-CO2 emissions, but in some individual evaluations, differences between tillage systems were noticed for C-CO2 evolution. Soil C-CO2 effluxes followed a bi-modal pattern, with peaks in October/November and February/March. The highest emission was recorded in the summer and the lowest in the winter. The C-CO2 effluxes were weakly correlated to air temperature and not correlated to soil moisture. Based on the soil C conservation indexes investigated, NT associated to intensive crop rotation was more C conserving than CT with monoculture.

Can non-inversion tillage and straw retainment reduce N leaching in cereal-based crop rotations?

Finding ways of reducing nitrate leaching in Northern Europe has become an extremely important task, especially under the projected climate changes that are expected to exacerbate the problem. To this end, two field experiments were established under temperate coastal climate conditions to evaluate the effect of tillage, straw retainment and cropping sequences, including cover crops, on nitrate leaching. The experiments were established in autumn 2002 on a loamy sand with 92 g clay kg −1 and a sandy loam with 147 g clay kg −1. The tillage treatments were stubble cultivation to 8–10 cm or 3–4 cm, direct drilling, or ploughing to 20 cm. The hypothesis was that (i) decreasing soil tillage intensity would decrease leaching compared to ploughing, (ii) leaving straw in the field would decrease leaching compared to removing straw, and (iii) a spring/winter crop rotation with catch crops would be more efficient in reducing nitrate leaching than a winter crop rotation. Overall, we were not able to confirm the three hypotheses. The effect of soil tillage on leaching might be blurred because the studied crop rotations had a high proportion of winter crops and because catch crops were grown whenever the alternative would have been bare soil in autumn and winter. The spring/winter crop rotation with catch crops was not found to be more efficient in reducing nitrate leaching than the winter crop rotation. In contrast, in a single year the winter crop rotation showed significantly lower leaching than the spring/winter crop rotations, probably due to the spring/winter crop rotation including peas, which may be considered a high-risk crop. Our study highlights that management practices that improve biomass production throughout the year are crucial in order to tighten the nitrogen cycle and thereby reduce nitrate leaching.

Herbicide tolerant canola systems and their impact on winter crop rotations

Canola is widely grown in Australia to provide diversity within winter crop rotations. Its production is heavily reliant on triazine tolerant varieties but Clearfield ® and conventional varieties are also significant components of the industry. Glyphosate tolerant varieties have been introduced, thereby providing an alternative technology to be incorporated into the farming systems. To evaluate the potential impact of the relative herbicide technologies, a comparison of herbicide tolerant canola weed management systems was undertaken at Wagga Wagga, Australia over a 5-year rotation. Near isogenic lines of conventional, glyphosate tolerant and triazine tolerant varieties were evaluated for their abilities to control annual ryegrass ( Lolium rigidum), the most challenging weed of temperate crops in Australia. Glyphosate tolerant and triazine tolerant canola achieved high levels of ryegrass control and attained higher yields than the conventional system. Glyphosate tolerant canola provided extra control of broadleaf weeds and also achieved better seed oil levels when compared with the other canola systems. There were positive flow-on weed management benefits for the remainder of the crop sequence from the weed control achieved in the initial crop, particularly following glyphosate tolerant canola. Subsequent control of volunteer canola in all treatments was readily achieved by using paraquat/diquat. The glyphosate tolerant weed management system was more profitable than the triazine tolerant system, although no allowance was made for technology costs as they were not known at the time of study. These outcomes demonstrate the potential value of herbicide tolerant canola to Australian farmers.

Prediction of surface runoff and soil loss in southeastern Norway using the WEPP Hillslope model

Yearly and daily surface runoff and soil loss simulated by the WEPP Hillslope model v. 2002.7 were compared with measurements from two different soil erosion plot sites in southeastern Norway. The soil at Bjørnebekk (Bj) was a levelled silty clay loam (2% organic matter) and the soil at Syverud (Sy) was a loam (5% organic matter). The plots at Bj were 21 m long and 8 m wide, while the plots at Sy were 30 m long and 7 m wide. Slope at both sites was 13%. Four management systems for grain production were used: autumn ploughing (AP), winter crop rotation (WCR), autumn harrowing (AH) and spring ploughing (SP). Hydraulic conductivity and soil erosion parameters were determined using WEPP-recommended equations based on measured soil parameters. In general, the WEPP Hillslope model simulated fewer runoff events than measured for all management systems during 1990–1998. Runoff events in winter were seldom predicted and small events (<5 mm) were mostly missed. To use the WEPP Hillslope model on Norwegian soils, where major soil loss events from arable land occur during late autumn, winter and early spring, improvements in winter hydrology calculations are needed. In particular calculations of soil frost development and infiltration into frozen soil need to be improved. The WEPP-recommended soil erosion parameter equations were unsuitable for these two Norwegian soils, especially for levelled soil.

Efeito de manejos de solo e de rotação de culturas de inverno no rendimento e doenças de trigo

O objetivo deste trabalho foi avaliar os efeitos de sistemas de manejo de solo e de rotação de culturas de inverno sobre o rendimento de grãos e sobre doenças radiculares do trigo. Foram comparados quatro sistemas de manejo de solo: plantio direto, cultivo mínimo, preparo convencional do solo com arado de discos mais grade de discos e preparo convencional de solo com arado de aivecas mais grade de discos. Na rotação de culturas, três sistemas foram utilizados: sistema I (trigo/soja), sistema II (trigo/soja e ervilhaca/milho ou sorgo) e sistema III (trigo/soja, aveia-preta ou aveia-branca/soja e ervilhaca/milho ou sorgo). O delineamento experimental foi em blocos ao acaso, com parcelas subdivididas e três repetições. A parcela principal foi constituída pelos sistemas de manejo de solo, e as subparcelas, pelos sistemas de rotação de culturas. O rendimento de grãos de trigo cultivado em plantio direto e em cultivo mínimo foi superior ao cultivado após preparo convencional do solo com arado de discos e com arado de aivecas. A rotação de culturas foi eficiente na redução de doenças do sistema radicular, resultando em aumento do rendimento de grãos de trigo.