.01% leaf N, respectively. It is possible that a N decrease in response to K rates occurred because K absorption increases demand of N ( Castaño et al., 2008 ). The N demand may have been even greater because the concentration of organic matter in the soil
Pear (Pyrus pyrifolia) fruits of `Whangkeumbae' were produced from the organic orchard at Yongam, southwestern Korea, which was managed by spraying with chitin incubated solution (CIS) 15 times from petal fall stage, mid-April to late August, to control pests and diseases during the growing season. The CIS contained about 50 kinds of chitin digestive and/or effective microorganisms and other organic/inorganic biologically active substances by incubating the mixtures at 30 °C for 7 days. The soil had standard levels of chemical and physical properties in Korea, as well as 3.0% to 4.0% organic matter. The organic fruits showed higher soluble solid contents, and fruit firmness was increased in comparison to conventional fruits. The organic fruit skin changed in color from yellow to brown, and black spot occurred; however, there was no difference in flesh tissues in terms of colors and textures. The phenolic compounds were significantly increased in organic fruits and leaves, with especially higher levels for fruit skin than for flesh tissues. Free radical levels dropped sharply in organic fruit, but slowly in conventional fruits. The results showed that the organic pear fruits have higher levels of antioxidant activity, and also showed the phenomena related to the change in fruit skin color from yellow to brown.
An important aspect of organic farming is to minimize the detrimental impact of human intervention to the surrounding environment by adopting a natural protocol in system management. Traditionally, organic farming has focused on the elimination of synthetic fertilizers and pesticides and a reliance on biological cycles that contribute to improving soil health in terms of fertility and pest management. Organic production systems are ecologically and economically sustainable when practices designed to build soil organic matter, fertility, and structure also mitigate soil erosion and nutrient runoff. We found no research conducted under traditional organic farming conditions, comparing bareground monoculture systems to systems incorporating the use of living mulches. We will be focusing on living mulch studies conducted under conventional methodology that can be extrapolated to beneficial uses in an organic system. This article discusses how organic farmers can use living mulches to reduce erosion, runoff, and leaching and also demonstrate the potential of living mulch systems as comprehensive integrated pest management plans that allow for an overall reduction in pesticide applications. The pesticide reducing potential of the living mulch system is examined to gain insight on application within organic agriculture.
An experiment was carried out at the Iowa State Univ., Neely-Kinyon Research Station (Greenfield, Iowa) to asses the possibility of growing organic radicchio rosso (Chicorium intybus var. silvestre) in Iowa and to determine the effectiveness of different organic fertilizers. The experiment was a factorial combination of three radicchio cultivars (very early, medium early, and early), three organic fertilizers treatments (non-fertilized control, liquid, and compost based), and two planting dates (11 July and 7 Aug). Treatments were arranged in a split plot design with four replicates. In each sub-plot, plants were transplanted, maintaining 30 cm between plants and 75 cm between rows (4.4 plant per m2). During the growth cycle the crop was managed according to typical production techniques adopted for lettuce. Beginning the first week after transplanting, canopy reflectance measurements were taken every 2 weeks until harvest, using a multispectral radiometer MSR 87 (Cropscan, Inc. Rochester Minn.). At harvest, total and marketable yields were measured and dry matter production was calculated. Yield loss was determined after 15 days of cold storage (4 °C). Cropscan measurement showed no differences among fertilizers treatments, mainly because of the high fertility of the soil (6% organic matter), but different growing patterns among radicchio types. The mediumearly type grew quicker than the other types, and showed the lowest percentage of bolted plants (<4%) and the least preharvest weight loss (5%). Moreover, radicchio demonstrated resistance from the hot and dry Iowa summer even without irrigation, representing a useful alternative crop for both organic and conventional farmers.
Chrysanthemum morifolium Ramat cv. White Spider CF2275 plants were grown in soilless media comprised of an andesitic cinder and pumice inorganic component mixed in 4 ratios with 4 organic components, namely, sphagnum peat, aged wood shavings, aged pineapple waste, and ground tree fern trunks (hapuu). The plant responses in the different media showed little difference from those in the control medium of equal parts of soil, peat, and perlite. Mixtures containing from 33 to 50% organic matter were satisfactory for plant growth. The physical and chemical characteristics of the media were within the ranges defined as satisfactory by previous researchers.
Field conditions associated with commercial cranberry (Vaccinium macrocarpon Ait.) production were simulated in greenhouse studies to determine the effect of soil surface characteristics on dichlobenil activity. Sand was compared with organic matter, in the form of leaf litter, as the surface layer. A seedling bioassay using alfalfa (Medicago sativa L.), a dichlobenil-sensitive plant, was employed to determine root growth response on herbicide-treated soil. When the herbicide was applied to a sand surface, root growth was greater as time after application elapsed, indicating loss of herbicide activity. Conversely, the presence of organic matter on the surface prolonged the activity of the herbicide. Composition of the surface layer was more important than the depth of the layer in determining herbicide persistence. The influence of cultural practices, such as the application of sand or the removal of surface debris, on herbicide activity should be considered when planning weed management strategies for cranberry production. Chemical name used: 2,6-dichlorobenzonitrile (dichlobenil).
A 3-year experiment was conducted to identify problems in Coachella Valley date palm (Phoenix dactylifera) orchards that limit vegetative growth, yield, and fruit quality. Major problems that were identified included soil compaction and stratification that restrict water permeation into the root zone, and low fertility as reflected by the low organic -matter content of the sandy soils. To eliminate the impact of these stresses on plant growth, yield, and fruit quality, a no-tillage alternative management system was introduced to replace the conventional practice of tillage that compacts the soil. No-till was coupled with the use of cover crops to enrich the soil with organic matter, fix N, recycle nutrients, and improve water holding capacity of the sandy soil. In already established orchards, an additional treatment—slip plowing—was also implemented to loosen the soil at lower depths to facilitate water permeation. The positive effects of the alternative system on the soil, tree growth, yield, and fruit quality will be presented.
Combinations of diuron, simazine, and terbacil were applied every year over 15 and 16 years to the same plots. Apple (Malu×domestica Borkh.) and peach (Prunus persica L.) trees then were planted 1 and 2 years following the last herbicide application. In general, apple-tree growth was not affected, but peach tree growth was reduced by some herbicide treatments. Peach-tree growth was reduced in plots treated with terbacil and soil organic matter was lowest in these plots. Time of last herbicide treatment did not affect apple- or peach-tree growth. The results indicated that reduced fruit-tree growth was associated with reduced soil organic matter and that residual terbacil may have inhibited peach-tree growth. Chemical names used: N′-(3,4-dichlorphenyl)-N,N-dimethylurea (diuron); 6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine (simazine); 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4(1H,3H)-pyrimidinedione (terbacil).
In Quebec, potato crops are largely grown on light acid soils altered by podzolization. In the plow layer, abundance of sesquioxides, low pH and low organic matter content produce high P-fixing capacity. Liming to pH not exceeding 5.6, organic matter additions and banding of P fertilizers are practices to improve the P status in the soil–plant system. Plant response to treatments could be diagnosed by yield evaluation and foliar analysis. Agricultural lime, dolomitic limestone and basalt were applied to an acid soil (pH 4.6). Ordinary superphosphate, biosuperphosphate, triple superphosphate, and diammonium phosphate impregnated with humic peat were banded at two rates. Highest tuber yield was 40 t·ha–1. There was no response to liming materials as pH did not exceed 4.9. There was a significant response to P fertilizers. Nutrient balance assessment of the foliage by Compositional Nutrient Diagnosis indicated a critical “d” value of 1.5 and a critical P index of 0.8.
In-season soil nitrate testing is most useful when there is reason to believe, based on field history, that N availability may be adequate. These reasons may include soil organic matter content, applied manure, compost, legumes in the rotation, or residual N fertilizer. Soil nitrate testing is not helpful when crops are grown on sandy, low organic matter content soils that are known from experience to be N deficient. Soil nitrate testing is useful for annual crops such as vegetables or corn for which supplemental N fertilization is a concern. Soil nitrate tests must be performed at critical crop growth stages, and the results must be obtained rapidly to make important decisions about the need for N fertilization. Soil nitrate-N (NO3-N) concentrations in the range of 25 to 30 mg·kg-1 (ppm) indicate sufficiency for most crops, but N fertilizer practice should be adjusted based on local extension recommendations.