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

Combining agronomic and breeding approaches for improved nutrient use efficiency

There is a strong need to improve agricultural nutrient use efficiency (NUE), but NUE is complex, and not even well defined. The abstract and presentation deal with how NUE is determined by the combination of Genetic, Environmental and Management factors (GxExM), and how genetics as well as crop management must be combined in order to achieve improved overall NUE

Brassicas in sustainable production and organic farming

Brassica plant species show some characteristics in their use of plant nutrients which make them different from most other crops. These characteristics often make brassicas difficult to grow in low-input systems with limited nutrient availability, but at the same time they also make some brassica species valuable tools for reducing nitrate leaching losses and improving N management in farming systems. The paper presents experimental results on brassica crops as main crops and cover crops

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

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

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

Comparing conventional and improved organic vegetable rotations, yields and nitrogen husbandry

During 2005 to 2009 three approaches to organic vegetable rotations were compared to a conventional rotation in an interdisciplinary project. The organic rotations differed in their reliance on animal manure vs. cover crops and intercrops, but the rotation of main vegetable and cereal crops were identical in the four rotations. One organic rotation (O1) relied on import of manure for supply of nutrients, in another (O2) cover crops were used to replace most of the manure import, and in (O3) also intercrops were grown to improve natural pest regulation. The yearly import of nitrogen were on average 149, 94, 28, and 28 kg N.ha-1 in C, O1, O2, and O3 respectively. On average the yield in the O1 system was 83% of the yield in the conventional system. In the O2 rotation the yield was the same, though the nutrient import was much lower, whereas the intercrops in O3 reduced the yield to 70% of the conventional fotation. The effect on single crops varied with organic yields ranging from 60% (onion) to almost 100% (carrots, oats) of conventional yields. Crop root growth varied strongly among crops with rooting depths of less than 0.4 m (onions) to more than 2 m (cabbage, rye, fodder radish catch crop). Root growth was unaffected by cropping system, but the inclusion of deep rooted catch crops and green manures in O2 and O3 increased the total root exploitation of the soil strongly. Thus, while the O1 and O2 systems had almost identical yields and N uptake there were large differences in their effects on soil N; e.g. the subsoil (1-2.5 m) N content was on average 18 kg N.ha-1 in the O2 compared 61 and 53 kg N.ha-1 in the C and O1 respectively, indicating strongly reduced N leaching losses in O2

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 root distribution and nitrogen uptake

Plant soil and atmosphere models are commonly used to predict crop yield and environmental consequence. Such models often include complex modelling modules for water movement, soil organic matter turnover and, above ground plant growth. However, the root modelling in these models are often very simple, partly due to a limited access to experimental data. We present a two-dimensional model for root growth and proliferation. The model focuses on annual crops, and attempt to model root growth of the crops and its significance for N uptake from different parts of the soil volume

Optimizing a green manure-based row cropping system for organic cereal production

A row cropping system with an increase of row distance to 24 cm increased the growth of undersown cover crops and allowed 1-2 passes of interow hoeing for weed control before sowing cover crops. The three-week delay sowing time was suitable for the growth of legume species. The new system significantly improved both grain yield and grain N content of the succeeding crop compared to the traditional cropping system