Crop production during the first course of an organic crop rotation trial in Denmark

Three factors are included in a factorial field experiment: 1) fraction of grass-clover and pulses in the rotation (crop rotation), 2) catch crop (with or without catch crop), and 3) manure (with or without animal manure). Manure is applied as slurry in rates corresponding to 40 % of the nitrogen demand. Grain yields for three sites and three years of the experiment are presented for two four-course rotations. One rotation has a green-manure crop, which is replaced by winter wheat in the other rotation. The use of manure significantly increased grain yield of the cereal crops in most cases. The positive effects of the catch crops were mainly observed in the spring cereals. The largest rotation yields were obtained in the crop rotation without a green manure crop. The positive effect of a green manure crop could not substitute for the yield decrease from leaving 25% of the area out of produc-tio

An organic vegetable crop rotation aimed at self-sufficiency in nitrogen

The paper describes the organic vegetable crop rotation. The ideas behind the design of the crop rotation, the use of green manures and catch crops, and how information on crop root growth has been used to try to design a crop rotation with a high NUE and minimal N leaching losses. The results from the first years of the rotation, in terms of yield and N uptake of the crops and of the content of inorganic N in the soil are presented

Learning from a long-term crop rotation experiment

A crop rotation experiment was established in 1996/97 at three locations representing differ-ent soil types and climates. Three factors were tested: i) crop rotation with different propor-tions of N2-fixing crops, ii) with and without a catch crop, and iii) with and without animal manure. A green manure crop increased yields in the following cereal crops, but at the rota-tional level, total yields were larger in crop rotations without a green manure crop. There were positive effects of animal manure and catch crops on yield. However, except for the coarse sandy soil, the yield effects of catch crops and animal manure decreased over time when a grass-clover green manure was included in the rotation. The problems with perennial weeds increased over time depending on crop rotation and use of catch crops. This stresses the im-portance of considering long-term effects in the evaluation of crop management measures

THE INVESTIGATION OF CROP WEEDINESS IN THE CROP ROTATION OF ORGANIC FARMING SYSTEM

Field experiments were conducted during the period of 2004 – 2006 at the Research and Study Farm „Vecauce”. The aim of the investigation was to establish the weediness’ dynamics of crops in a six-field crop rotation of an organic farming system. The field was certified as being organic. Crop rotation: 1. triticale/ rye (for green manure in spring), 2. oil radish (for green manure)/ rye (for green manure in autumn), 3. potatoes, 4. oats, 5. vetch-oats mix (for green forage) with an undersown mixture of red clover and timothy, 6. red clover and timothy. Conventional soil tillage was done according to the requirements of the crops. The weeds were counted two times during the vegetation period of crops: at the early development stages of crops (for instance, at the tillering of cereals) and before the crop harvesting. The composition of weed flora comprised from 59 species in the crops’ stands. The annual dicotyledonus were dominating groups of the weed flora. The most abundant weeds were lambsquarters (Chenopodium album L.), quackgrass (Elytrigia repens (L.) Nevski), common yellow rocket (Barbarea vulgaris R. Br.p.p.). The significantly smaller amount of weeds among crop rotation links was observed in the link rye/ oil radish/ rye – potatoes – oats. Much worse suppression of weeds was obtained in the crop rotation link red clover and timothy – triticale/ rye – oil radish/ rye. The number of weeds in the fields of crop rotation in the organic farming system is dependent on the cultivated crops, the succession of crops in the crop rotation links and crop cultivation technologies

THE ECONOMIC IMPORTANCE OF CROP ROTATION SYSTEMS: EVIDENCE FROM THE LITERATURE

Agricultural sustainability requires that the individual farm firm be competitive and profitable while simultaneously enhancing environmental quality and the natural resource base upon which the farm firm and agricultural economy depends. The reliance of conventional agriculture systems on purchased inputs external to the firm presents possible challenges to the long-term sustainability of the system. Crop rotation systems are one cropping system alternative that can reduce agriculture's dependence on external inputs through internal nutrient recycling, maintenance of the long-term productivity of the land, and breaking weed and disease cycles. Decision criteria to choose among competing crop rotation systems can include impact on soil quality and fertility, environmental quality, and farm profitability. However, most of the comparative economic analysis work reviewed for this paper considered only farm profitability as a criterion to rank alternative crop rotation systems. Most rotation research is focused around a target crop that is the foundation for the crop rotation system. When corn is the target crop, comparative profitability performance of continuous corn vs. corn grown in rotation showed that neither system is consistently more profitable than another. Corn yield in Michigan does respond favorably to crop diversity. Wheat as the target crop in rotation tends to outperform continuous wheat both in terms of profitability and income risk. Sugar beet prices hold the key in determining the profitability ranking of alternative sugar beet-based crop rotations. Potato in rotations tends to outperform continuous potato both in terms of yield and profitability. Future studies addressing the economic performance of crop rotations need to consider the environmental benefits/costs both on and off the farm site that accrue to society. Keywords: Agricultural sustainability, external inputs, soil quality and fertility, environmental quality, crop rotations, comparative economic analysis, farm profitability.Agricultural sustainability, external inputs, soil quality and fertility, environmental quality, crop rotations, comparative economic analysis, farm profitability., Crop Production/Industries,

Modelling risk in farm planning

In this article a mathematical model is presented to assist management decisions on an integrated crop and livestock farm. Risk is incorporated into the model as the negative deviation of the actual gross income from the expected value of an activity's gross income. The model includes crop production (permitting and optimising a crop rotation system), dairy production and wool sheep production. Relevant data from a farm in the Swartland region of the Western Cape were used to test and validate the model. The results show that the adoption of crop rotation is superior in terms of gross margin to that generated from a mono-crop strategy. Empirical results also indicate that the complex interrelationships involved in a mixed crop-livestock farm operation play a major role in determining optimal farm plans. These complex interrelationships favour the introduction of crop rotation in the crop production activities of the farm under investigation. Solutions of the model with risk indicate that the crop rotation strategy and animal production levels are sensitive to different risk levels, and that the incorporation of risk greatly affects the level of land allocation to crop rotation and animal production level of the farm. Finally, the results suggest that the introduction of crop rotation is of paramount importance in improving the profitability and sustainability of the farm, thus the inclusion of forage crops such as medics into the integrated crop-livestock production is beneficial for sustained profitability.Farm Management, Risk and Uncertainty,

Genome scan of Diabrotica virgifera virgifera for genetic variation associated with crop rotation tolerance

Crop rotation has been a valuable technique for control of Diabrotica virgifera virgifera for almost a century. However, during the last two decades, crop rotation has ceased to be effective in an expanding area of the US corn belt. This failure appears to be due to a change in the insect's oviposition behaviour, which, in all probability, has an underlying genetic basis. A preliminary genome scan using 253 amplified fragment-length polymorphism (AFLP) markers sought to identify genetic variation associated with the circumvention of crop rotation. Samples of D. v. virgifera from east-central Illinois, where crop rotation is ineffective, were compared with samples from Iowa at locations that the behavioural variant has yet to reach. A single AFLP marker showed signs of having been influenced by selection for the circumvention of crop rotation. However, this marker was not diagnostic. The lack of markers strongly associated with the trait may be due to an insufficient density of marker coverage throughout the genome. A weak but significant general heterogeneity was observed between the Illinois and Iowa samples at microsatellite loci and AFLP markers. This has not been detected in previous population genetic studies of D. v. virgifera and may indicate a reduction in gene flow between variant and wild-type beetles

Designing crop rotations in organic and low-input agriculture: Evaluation of pre-crop effects

In this overview, the preceding effects of crop pairs are classified by establishing schematic diagrams for use in crop rotation planning in low external input or organic agricultural systems. Results from previous crop rotation trials and earlier diagrams cited in the literature were evaluated in order to classify the succession effects for more than 25 main crop species. Additional information about several cultivation remarks were annotated in small letters for every crop sequence. In a tabular overview, the crop species were arranged into three main categories according to the different duration of their pre-crop effects: I. N fixing, soil fertility increasing legumes and legume-grass mixtures; II. N depleting, intense soil fertility reducing non-legumes; III. modest soil fertility reducing non-legumes

Accounting for agronomic rotations in crop production: A theoretical investigation and an empirical modeling framework

As far as crop acreage choices are concerned, a consensus seems to exist among agricultural scientists and extension agents: crop rotation effects and the related constraints are major determinants of farmers’ crop choices. Crop rotation effects are inherently dynamic. They are generally ignored in multicrop models with land as an allocable input found in the literature since most of these models are developed within a static framework. The aim of this paper is twofold (i) to propose a new approach and tools for investigating dynamic crop acreage choices accounting for crop rotation benefits and constraints and (ii) to illustrate the impacts of crop rotation effects and constraints on farmers’ acreage choices through simulation examples. The models proposed in this paper are sufficiently simple for being empirically tractable either in simulation studies or in econometric and mathematical programming analyses. Our simulation results tend to show responses of the optimal dynamic acreages to simple price shocks which are much more complex than those implied by static models. They also demonstrate that farmers’ perceptions of the future economic context are crucial determinants of their acreage choices. In fact current acreage choices may appear suboptimal in a static sense but are fully consistent when dynamic effects of crop rotations are specified.Crop rotation, Dynamic programming, Acreage choice, Crop Production/Industries, Land Economics/Use, Q12, D21, D24, D92,