Utilising differences in rooting depth to design vegetable crop rotations with high nitrogen use efficiency (NUE)

A number of methods involving plant or soil analysis or modelling have been developed to optimise N fertilization of vegetable crops. The methods aim at improving the NUE of each single crop, but do not really consider the crop rotation as such. Various measures can be used to increase the NUE of the crop rotation; measures that can be combined with the methods aimed at optimising NUE of each single crop. The aims of the paper are to discuss the methods for optimising NUE at the crop rotation level and to present examples of how this can be done. The main methods discussed are 1) how can crops with different rooting depth be optimally placed in a cropping sequence and 2) how can catch crops be introduced to optimise NUE. Results show that if N left in the soil after harvest on one crop is retained in the soil until spring, it will normally be found in deeper soil layers. Therefore rooting depth of the vegetable crops is important. It is illustrated that by placing deep-rooted crops in the crop rotation preferentially where much N was left in the soil in the previous year can strongly increase the utilisation of the N residues. It is also shown how catch crops can be used to maintain a high NUE, especially in situations where the farmers choose to grow shallow-rooted vegetables even though much N may be available in deeper soil layers

Root growth and soil nitrogen depletion by onion, lettuce, early cabbage and carrot

Experiments examining root growth, the utilization of N and the effect of green manures were carried out on four vegetable crops. Large differences were observed both in rooting depth penetration rates, and in final rooting depth and distribution. Onion had a very low depth penetration rate, carrot an intermediate rate, and lettuce and cabbage showed high rates. A combination of depth penetration rates and duration of growth determined rooting depth at harvest. Therefore, lettuce, which had a very short growing season, had a shallow root system at harvest, whereas carrot with a lower depth penetration rate but a long growing season had deep rooting at harvest. The final rooting depth of the vegetables varied from approximately 0.3 m for onion to more than 1.0 m for carrot and early cabbage. Carrot and cabbage were able to utilize N from deeper soil layers, not available to onion and lettuce. The ability of green manure crops to concentrate available N in the upper soil layers was especially valuable when they were grown before the two shallow rooted crops

Effect of crop management practices on the sustainability and environmental impact of organic and low input food production systems

While organic farming can reduce many of the environmental problems caused by agriculture, organic farming also includes some practices which are questionable in terms of environmental effects. Organic farming practices (rotations, fertilisation regimes, cover crop use) can differ significantly and this leads to large differences in its environmental effects. This leaves considerable scope to improve the environmental effects of organic farming. The environmental aspects of organic farming are discussed, and model simulations are used to illustrate how even moderate changes in organic rotations can have large effects on sustainability, here measured by a simple index of nitrogen lost by leaching relative to nitrogen harvested by the crops. In WP3.3.4 we are working to improve model simulation of organic rotations, and in WP7.1 we are making environmental assessment of organic cropping practices tested in the QLIF project, using model simulations and other approaches

Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (Ninorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil Ninorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day)1 C)1. Shallow placement of soil Ninorg resulted in greater N uptake in the shallow-rooted leek and potato. Deep placement of soil Ninorg resulted in greater rates of root depth penetration in the deep-rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil Ninorg on root distribution and capacity for depletion of soil Ninorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency

Modelling diverse root density dynamics and deep nitrogen uptake — a simple approach

We present a 2-D model for simulation of root density and plant nitrogen (N) uptake for crops grown in agricultural systems, based on a modification of the root density equation originally proposed by Gerwitz and Page in J Appl Ecol 11:773–781, (1974). A root system form parameter was introduced to describe the distribution of root length vertically and horizontally in the soil profile. The form parameter can vary from 0 where root density is evenly distributed through the soil profile, to 8 where practically all roots are found near the surface. The root model has other components describing root features, such as specific root length and plant N uptake kinetics. The same approach is used to distribute root length horizontally, allowing simulation of root growth and plant N uptake in row crops. The rooting depth penetration rate and depth distribution of root density were found to be the most important parameters controlling crop N uptake from deeper soil layers. The validity of the root distribution model was tested with field data for white cabbage, red beet, and leek. The model was able to simulate very different root distributions, but it was not able to simulate increasing root density with depth as seen in the experimental results for white cabbage. The model was able to simulate N depletion in different soil layers in two field studies. One included vegetable crops with very different rooting depths and the other compared effects of spring wheat and winter wheat. In both experiments variation in spring soil N availability and depth distribution was varied by the use of cover crops. This shows the model sensitivity to the form parameter value and the ability of the model to reproduce N depletion in soil layers. This work shows that the relatively simple root model developed, driven by degree days and simulated crop growth, can be used to simulate crop soil N uptake and depletion appropriately in low N input crop production systems, with a requirement of few measured parameters

Kompost af byaffald er velegnet som P-gødning og til jordforbedring

I løbet af få år bliver det formentlig forbudt at bruge konventionel husdyrgødning til økologisk planteproduktion, og derfor er det nødvendigt allerede nu at undersøge alternative gødningskilder. Én mulighed kunne være recirkulering af næringsstoffer gennem kompost af forskellige typer by-affald. Dette er netop blevet undersøgt i projektet RoCo, som er en del af forskningsprogrammet Organic RDD 2

Horizontal activites. QLIF subproject 7: Horizontal activities

QLIF subproject 7 represents four horizontal activities common to the project, namely: • Environmental and sustainability audits • Cost-benefit analyses and socio-economic impact assessments • Dissemination and technology transfer • Training of graduate and postgraduate researchers Activities in the horizontal research have shown that organic crop production systems generally are more energy-efficient and have lower greenhouse gas emissions than the conventional production. In terms of dissemination the QLIF website has been central and the QLIF newsletter has attracted more than 1000 subscribers. Coupling of the website with the open access database Organic Eprints provides a prospective source of project information that can be accessed also by future stakeholders in organic and low-input systems. Training events arranged annually for students have contributed to proliferation of skills and knowledge gained in QLIF. Also, these events have served to mediate the attitude needed for research in organic and low-input farming

¿Cómo influyen las limitaciones geométricas en las pautas de migración?

Null models exclusively invoking geometric constraints have recently been demonstrated to provide new insight as to what explains geographic patterns of species richness and range size distribution. Analyses of migration patterns have traditionally been conducted in the absence of appropriate simulations and analytical models. Here we present a null model exclusively invoking geometric constraints and a more advanced analytical model incorporating spread along a migration direction that allow investigation of the influence of physiographical and physiological boundaries for terrestria taxa, with ocean and sea as geometric constraints, in relation to observed patterns of migration. Our models take into account the low recovery probability of terrestrial taxa over sea. The null model was not found to explain any of the directional variation in the ring–recoveries, but when comparing the distribution of data modeled using a simple clock–and–compass model with distributions of ring–recoveries, geometric constraints were found to explain up to 22% of the variation in ring–recoveries. However, the assumed directional concentrations per step used in the model were much higher than expected, and the qualitative fit of the model was rather poor even when non–terrestrial sites of recoveries were excluded.Recientemente se ha demostrado que los modelos nulos que recurren exclusivamente a las limitaciones geométricas proporcionan nuevas aportaciones para explicar las pautas geográficas que definen la riqueza de las especies y la distribución por tamaños según el rango. Tradicionalmente, los análisis de pautas de migración se han realizado sin emplear simulaciones ni modelos analíticos apropiados. En este estudio presentamos un modelo nulo que se basa exclusivamente en limitaciones geométricas, así como un modelo analítico más avanzado que incorpora la dispersión y una dirección de migración, lo que permite investigar la influencia de los límites fisiográficos y fisiológicos en los taxones terrestres, tomando el océano y el mar como limitaciones geométricas, con relación a las pautas de migración observadas. Los modelos que hemos empleado tienen en cuenta la baja probabilidad de recuperación de los taxones terrestres en el mar. El modelo nulo no pudo explicar ninguna de las variaciones direccionales en las recuperaciones de anillas; sin embargo, al comparar la distribución de los datos modelados utilizando un modelo simple de reloj y brújula con distribuciones de recuperaciones de anillas, se constató que las limitaciones geométricas podían explicar hasta el 22% de la variación en las recuperaciones de anillas. Pese a ello, las concentraciones direccionales por pasos que se presupusieron en el modelo fueron muy superiores a lo previsto, y el ajuste cualitativo del mismo resultó bastante deficiente cuando se excluyeron los emplazamientos de recuperaciones no terrestres

Crossing the Logarithmic Barrier for Dynamic Boolean Data Structure Lower Bounds

This paper proves the first super-logarithmic lower bounds on the cell probe complexity of dynamic boolean (a.k.a. decision) data structure problems, a long-standing milestone in data structure lower bounds. We introduce a new method for proving dynamic cell probe lower bounds and use it to prove a $\tilde{\Omega}(\log^{1.5} n)$ lower bound on the operational time of a wide range of boolean data structure problems, most notably, on the query time of dynamic range counting over $\mathbb{F}_2$ ([Pat07]). Proving an $\omega(\lg n)$ lower bound for this problem was explicitly posed as one of five important open problems in the late Mihai P\v{a}tra\c{s}cu's obituary [Tho13]. This result also implies the first $\omega(\lg n)$ lower bound for the classical 2D range counting problem, one of the most fundamental data structure problems in computational geometry and spatial databases. We derive similar lower bounds for boolean versions of dynamic polynomial evaluation and 2D rectangle stabbing, and for the (non-boolean) problems of range selection and range median. Our technical centerpiece is a new way of "weakly" simulating dynamic data structures using efficient one-way communication protocols with small advantage over random guessing. This simulation involves a surprising excursion to low-degree (Chebychev) polynomials which may be of independent interest, and offers an entirely new algorithmic angle on the "cell sampling" method of Panigrahy et al. [PTW10]

Catch Crops in Organic Farming Systems without Livestock Husbandry - Model Simulations

During the last years, an increasing number of stockless farms in Europe converted to organic farming practice without re-establishing a livestock. Due to the lack of animal manure as a nutrient input, the relocation and the external input of nutrients is limited in those organic cropping systems. The introduction of a one-year green manure fallow in a 4-year crop rotation, including clover-grass mixtures as a green manure crop is the classical strategy to solve at least some of the problems related to the missing livestock. The development of new crop rotations, including an extended use of catch crops and annual green manure (legumes) may be another possibility avoiding the economical loss during the fallow year. Modelling of the C and N turnover in the soil-plant-atmosphere system using the soil-plant-atmosphere model DAISY is one of the tools used for the development of new organic crop rotations. In this paper, we will present simulations based on a field experiment with incorporation of different catch crops. An important factor for the development of new crop rotations for stockless organic farming systems is the expected N mineralisation and immobilisation after incorporation of the plant materials. Therefore, special emphasise will be put on the simulation of N-mineralisation/-immobilisation and of soil microbial biomass N. Furthermore, particulate organic matter C and N as an indicator of remaining plant material under decomposition will be investigated