The value of catch crops and organic manures for spring barley in organic arable farming

The effect of nitrogen (N) supply and weeds on grain yield of spring barley was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three different soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: (1) catch crop (with and without), and (2) manure (with and without). The crop rotation included grass-clover as a green manure crop. Animal manure was applied as slurry in rates corresponding to 40% of the N demand of the cereal crops.

Application of 50 kg NH₄-N ha⁻¹ in manure (slurry) increased average barley grain DM yield by 1.0–1.3 Mg DM ha⁻¹, whereas the use of catch crops (primarily perennial ryegrass) increased grain DM yield by 0.2–0.4 Mg DM ha⁻¹ with the smallest effect on the loamy sand and sandy loam soils and the greatest effect on the coarse sandy soil. Model estimations showed that the average yield reduction from weeds varied from 0.2 to 0.4 Mg DM ha⁻¹ depending on weed species and density. The yield effects of N supply were more predictable and less variable than the effects of weed infestation. The infestation level of leaf diseases was low and not a significant source of yield variation.

The apparent recovery efficiency of N in grains (N use efficiency, NUE) from NH₄-N in applied manure varied from 29 to 38%. The NUE of above-ground N in catch crops sampled in November prior to the spring barley varied from 16 to 52% with the largest value on the coarse sandy soil and the smallest value on the sandy loam soil. A comparison of grain yield levels obtained at the different locations with changes in soil organic matter indicated a NUE of 21–26% for soil N mineralisation, which is smaller than that for the mineral N applied in manure. However, this estimate is uncertain and further studies are needed to quantify differences in NUE from various sources of N.

The proportion of perennial weeds in total biomass increased during the experiment, particularly in treatments without manure application. The results show that manure application is a key factor in maintaining good crop yields in arable organic farming on sandy soils, and in securing crops that are sufficiently competitive against perennial weeds.     

Nitrous oxide emissions and controls as influenced by tillage and crop residue management strategy

Mixed responses of soil nitrous oxide (N₂O) fluxes to reduced tillage/no-till are widely reported across soil types and regions. In a field experiment on a Danish sandy loam soil we compared N₂O emissions during winter barley growth following five years of direct drilling (DD), reduced tillage (RT) or conventional tillage (CT). Each of these tillage treatments further varied in respect to whether the resulting plot crop residues were retained (+Res) or removed (−Res). Sampling took place from autumn 2007 to the end of spring 2008. Overall N₂O emissions were 27 and 26% lower in DD and RT, respectively, relative to N₂O emissions from CT plots (P < 0.05). We observed that in residue removal scenarios N₂O emissions were similar for all tillage treatments, but in residue retention scenarios N₂O emissions were significantly higher in CT than in either DD or RT (P < 0.05). Irrespective of residue management, N₂O emissions from DD and RT plots never exceeded emissions from CT plots. Retention of residue was estimated to reduce emissions from DD plots by 39% and in RT plots by 9%, but to increase N₂O emissions from the CT plots by 35%. Relative soil gas diffusivity (Rdiff), soil NO₃-N, soil temperature, tillage and residue were important driving factors for N₂O emission (P < 0.05). A multiple linear regression model using Rdiff to represent the water factor explained N₂O emissions better than a water-filled pore space (WFPS) based model, suggesting a need for review of the current use of WFPS in N₂O prediction models. We conclude that on light textured soils, no-till has the potential for reducing N₂O emissions when crop residues are returned to the soil.     

Relationship between MALDI-TOF analysis of beta-CN f193-209 concentration and sensory evaluation of bitterness intensity of aged cheddar cheese

An internal standard method was previously developed to measure the concentration of a synthetic bitter peptide, beta-CN f193-209, by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The objective of this study was to evaluate the relationship between beta-CN f193-209 concentration in an aqueous extract of aged Cheddar cheese and bitterness intensity of the cheese. Concentrations of beta-CN f193-209 in cheese extracts were determined by MALDI-TOF at 0, 120, 180, and 270 days. Trained panels evaluated the bitterness intensity of the cheeses at 180 and 270 days. Correlation coefficients between MALDI and sensory data at 180 and 270 days were 0.803 and 0.554, respectively. The decreased correlation may be due to the presence of other bitter peptides more responsible for bitterness at longer aging or the production of compounds that mask bitterness intensity.     

The effect of tillage intensity on soil structure and winter wheat root/shoot growth

Despite a vast amount of data on the effect of tillage on crop productivity, surprisingly there is little detailed information available on the influence on below and aboveground crop growth dynamics. Such information is essential for developing sustainable cropping systems. The objective of this study was to investigate the effect of tillage intensity on crop growth dynamics and soil structure. A tillage experiment was established in autumn 2002 on two Danish sandy loams (Foulum and Flakkebjerg) in a cereal‐based crop rotation. The tillage systems included in this study were direct drilling (D), harrowing 8–10 cm (H_8‐10), and ploughing (P). A single‐disc drill was used in the H_8‐10 and D treatments and a traditional seed drill in the P treatment. Measurements were carried out in 2004–05 and 2005–06 and winter wheat was grown in both years (first and second year winter wheat). Shoot and root growth was followed during the growing seasons using spectral reflectance and mini‐rhizotron measurements, respectively. A range of soil physical properties were measured. We found decreased early season shoot and root growth with decreasing tillage intensity. Differences diminished later in the growing season, although significant treatment effects were observed throughout the growing season for the second year winter wheat. The formerly ploughed layer in the D and H_8‐10 treatments was noticeably compacted as indicated by increases in both penetration resistance and bulk density. Nitrate leaching increased with decreasing tillage intensity for the first year winter wheat at Foulum. In general ploughing resulted in the highest grain yields. This study highlights the important interaction between soil structure and crop growth dynamics.     

Flower greening in phytoplasma-infected Hydrangea macrophylla grown under different shading conditions

To determine the effect of light intensity on flower greening, the Japanese hydrangea phyllody (JHP) phytoplasma-infected hydrangea cultivars ‘Midori’, ‘Libelle’, ‘Rosea’ and ‘Madame E. Mouillere’ plants were grown under different shade conditions. In the first-year experiment, the results indicate that the flowers of the JHP-phytoplasma-infected hydrangea become green under shaded conditions (70% and 49% sunlight intensities). On the other hand, under full sunlight intensity (100% sunlight intensity), the flowers of ‘Midori’, ‘Rosea’, and ‘Libelle’ plants were blue, pink or white. To calculate the percentage of flower greening, inflorescences of these plants were separated and divided into individual flowers, and classified into four types by green-area ratio, calculated using Adobe Photoshop. Under shading with one sheet of cheesecloth (70% sunlight intensity), the inflorescences of ‘Midori’, ‘Libelle’ and ‘Madame E. Mouillere’ plants were composed of more than 40% completely green flowers (0.8 ≦ green-area ratio), whereas those of ‘Rosea’ plant had 0% completely green flowers. Under shading with two sheets of cheesecloth (49% sunlight intensity), the inflorescences of ‘Midori’, ‘Libelle’ and ‘Madame E. Mouillere’ plants had more than 75% completely green flowers; ‘Rosea’ plants had 28%. In the second-year experiment, under full sunlight intensity, ‘Midori’ plants had four types of flower depending on their green-area ratio, namely, completely blue or pink, pink-green, greenish and completely green flowers. Under shading with two sheets of cheesecloth, ‘Midori’ plants had more than 90% completely green flowers. The JHP-phytoplasma could not be identified by PCR analysis in flowers with a green-area ratio = 0 (completely blue/pink/white flowers). On the other hand, in flowers with a green-area ratio > 0, the JHP-phytoplasma was detected by PCR analysis. Thus, we conclude that shading enhances flower greening in hydrangea by increasing the JHP-phytoplasma concentration in the flowers.     

Leaching of soil organic carbon and nitrogen in sandy soils after cultivating grass-clover swards

Several studies have focused on the formation and losses of dissolved organic matter in forest systems, whereas a limited number have dealt with this aspect in agricultural soils. The purpose of this study was to estimate the leaching of dissolved organic carbon (DOC) and nitrogen (DON), with focus on the period after cultivating grass-clover swards. Grass-clovers were ploughed in the spring prior to sowing cereals followed by either catch crops or bare soil. The concentrations of DOC and DON decreased with soil depth and ranged at 90-cm soil depth between 7 and 21 mg C L⁻¹ and between 1 and 3 mg N L⁻¹, respectively, in a sandy loam soil, and between 16 and 63 mg C L⁻¹ and between 1 and 10 mg N L⁻¹, respectively, in a coarse sandy soil. The resulting DOC/DON ratios were in the range between 2 and 42, with higher values in the coarse sandy soil than in the sandy loam soil. The total percolation was 218 mm in the sandy loam soil and 596–645 mm in the coarse sandy soil, which resulted in an annual leaching of 22–40 kg DOC ha⁻¹ year⁻¹ and 3–4 kg DON ha⁻¹ year⁻¹ in the sandy loam soil, and 174–310 kg DOC ha⁻¹ year⁻¹ and 10–31 kg DON ha⁻¹ year⁻¹ in the coarse sandy soil. It was shown that higher amounts of DOC were lost by leaching under the catch crops than from bare soil, that losses of DON were higher from bare soil than from soils with catch crops and that DON contributed significantly to the total N loss. Thus, DON needs to be taken into account in N-balance calculations.     

Antibody response to Mycoplasma capricolum subsp. capripneumoniae bacterium in small holder dairy goats in Tanzania

Contagious caprine pleuropneumonia (CCPP), an Office International des Epizooties listed disease, can cause significant levels of morbidity and mortality in goats in Africa, the Middle East, and Western Asia. A cross-sectional study was conducted to determine the seroprevalence of CCPP, in two contrasting administrative districts of northern Tanzania, namely, Babati and Arumeru. A total of 337 serum samples were collected from January to July 2010, from apparently clinically healthy unvaccinated dairy goats breeds of different ages and sexes. Samples were subjected to monoclonal antibody-based competitive enzyme-linked immunosorbent assay for the specific measurement of antibodies to Mycoplasma capricolum subsp. capripneumoniae bacterium. The overall animal flock and village-level seroprevalence of CCPP was found to be 3.3 % [95 % confidence interval (CI)?=?1.6–5.8], 9.6 % (95 % CI?=?4.7–16.9), and 31.5 % (95 % CI?=?15.6–56.5), respectively. There was no evidence (p?=?0.659) of differences in seroprevalence between samples from the two administrative locations. Despite the fact that there was no significant difference (p?>?0.05) in seropositivity between sex and age and between breeds sampled, there was a significant difference (p?<?0.05) in seropositivity between the different physiological status groups examined with the non-lactating (dry) category of goats showing a higher seroprevalence. The findings of this survey revealed evidence of dairy goat exposure to M. capricolum subsp. capripneumoniae, although at a low prevalence. It is therefore advisable to include CCPP serology in the seromonitoring program so as to give a better indication of flock immunity. This should lead to the establishment of appropriate CCPP control measures in smallholder dairy goat flocks, which are increasingly being recognized for their value as a vital source of livelihood for resource poor livestock keepers in Tanzania.     

Milling Value of Sorghums Compared by Adjusting Yields to a Constant Product Color

A method of comparing milling values of sorghum by adjusting yields to standard L values was developed. The milling values of ‘Dorado’ (an excellent food-type sorghum variety), ‘ATx399 × RTx430’ (a commercial red sorghum hybrid) and three ‘Warner 902W’ (commercial white food type hybrids with different levels of weathering designated W-1, W-2, and W-3) were determined using a tangential abrasive dehulling device for various times. Color (L, a, b) was measured on the decorticated grain (grits) and the ground grits (flour). The yields (by weight) of flours adjusted to an L value of 85 were 93, 88, 86, 84, and 70% for Dorado, W-2, W-1, W-3, and red, respectively. The b (yellow) values were highest for red and lowest for Dorado. The grits yields were 96, 89, 84.5, 81.5, and 56.5% when adjusted to an L of 67 for Dorado, W-2, W-1, W-3, and red sorghums, respectively. Milling yields expressed at comparable flour or grit color clearly demonstrate that white food-type sorghums have significantly better milling yields than red sorghums. Adjusting milling yields to a standard L value is an accurate and easy way to compare milling properties of sorghums for yield and product color.