Effect of alley cropping with Leucaena leucocephala and fertilizer application on yield of vegetable crops

Field experiments were conducted to investigate the effect of alley cropping vegetable crops with Leucaena leucocephala (Lam.) de Wit for two seasons on a sandy loam Oxic paleustalf in southwestern Nigeria. Four vegetable crops (Amaranthus cruentus L.; Celosia argentea L.; Okra, Hibiscus esculentus L.; and tomato, Lycopersicon esculentum Mill.) were grown in control plots and in 4-m wide alleys between established Leucaena hedgerows without and with fertilizer (30 N-13 P-24 K kg ha^–1). Leucaena prunings yielded large dry biomass and nutrients during both seasons. Yield of four vegetable crops responded more to fertilizer in control than in alley cropped treatments. Better yield of vegetables in alley cropped plots was in part due to following effect of the Leucaena hedgerows. Fertilizer application increased mean yields of Amaranthus, Celosia, okra and tomato by 325, 164, 47 and 94% in control plots and by 36, 26, 4 and 20% in alley cropped plots, respectively. For both seasons, yields were not significantly different between alley cropped with and without fertilizer and the control with fertilizer treatments. Yield was least in control without fertilizer. Alley cropping with Leucaena can reduce fertilizer requirement for vegetable production. Cost and return analysis using 1988 prices indicated that alley cropping with vegetable crops can be profitable.c/o Miss Maureen Larkin, L. W. Lambourn & Company, 26 Dingwall Road, Croydon CR9 3EE, England     

The use of the ingrowth core method for measuring root production of arable crops — influence of soil conditions inside the ingrowth core on root growth

The ingrowth core method can be used to measure root gross growth (i.e. root production). A mesh bag filled with root free soil is buried into the root zone. After about 14 days, the bag is pulled out and root length inside the core can be determined. An objection against this method is the inability to obtain the same soil conditions inside the bag as outside, which can result in different root growth pattern in the ingrowth core compared to the bulk soil. To study this, mesh bags were buried in a stand of oilseed rape and were filled with soil at different nitrate, phosphate, moisture, and bulk density levels. Results showed that root growth was only influenced by a high nitrate content and a high soil density in the cores, which resulted in higher and lower root length densities (RLD), respectively. In a long‐term ingrowth experiment similar root length densities in the cores and in the bulk soil were measured, indicating that there were no root growth enhancing or impeding conditions inside the ingrowth cores. The conclusion is drawn, that the ingrowth core method gives reliable results, provided the N content and the soil density inside the bags are comparable to the bulk soil.     

A comparison of plant available nutrients on decomposed granite cut slopes and adjacent natural soils

Decomposed granite (DG) slopes are often difficult to revegetate after existing topsoil and vegetative cover have been removed. In this study, naturally vegetated soils and denuded DG cut slopes were evaluated to compare edaphic (soil-related) conditions that may differ between the vegetated and non-vegetated states. Potential plant nutrient deficiencies were evaluated by soil nutrient extraction, plant tissue analysis and by greenhouse bioassay methods. The DG cut slopes have approximately one-quarter to one-half the clay content, soil organic matter, water-holding capacity, and total and available nitrogen (N) of the adjacent natural soils. Soil extraction tests for phosphorus (P) availability gave variable results, but a growth response to P amendment was observed in a greenhouse bioassay. The native topsoils and the DG cut slope materials had non-limiting levels of pH, exchangeable Ca, Mg and K, and total P. Cation exchange capacity and sulfate–sulfur (S) were low but similar between the two soil groups. Principle nutrient limitations are interpreted to be N, P, and possibly S and boron (B), in order of decreasing severity. Based on these results, we conclude that the removal of humified soil organic matter on the cut slopes reduces plant growth directly by lowering several of these essential nutrients, and indirectly by decreasing the soil's water-retention and infiltration capacity. Soil organic matter is viewed as a critical factor and major contrast between barren and revegetated DG materials. © 1998 John Wiley & Sons, Ltd.     

Potassium Dynamics in the Rhizosphere and K Efficiency of Crops

Nutrient efficiency is defined as the ability of plants to obtain higher relative yields at low nutrient supply compared to other species. The size of the root system, the physiology of uptake and the ability of plants to increase K solubility in the rhizosphere are considered as mechanisms of uptake efficiency. In a solution experiment wheat and sugar beet were more K efficient than potato because wheat had a large root system and both species had an efficient uptake physiology. Also in soil wheat was uptake efficient because of a large root system, whereas the efficiency of sugar beet was caused by the ability to increase K solubility. This could be shown by the use of a model to describe K dynamics in the rhizosphere.     

Comparison of slow‐release nitrogen yield from organic soil amendments and chemical fertilizers and implications for regeneration of disturbed sites

Soil amendments are commonly used to regenerate nutrient levels on disturbed construction sites or mined lands prior to revegetation. Management of nitrogen (N) inputs to the degraded substrates is difficult because the low level of ambient fertility on disturbed substrates requires large total N inputs to sustain revegetative growth, but it also requires low N bioavailability in order to avoid weedy invasion and eutrophication of local watersheds. Commonly available soil amendment materials have a wide variety of N contents and release rates, making specification of appropriate N amendments difficult. We compared N release rates of a variety of organic‐based soil amendments and chemical fertilizers in long‐term aerobic incubation chambers in the lab and at a field revegetation site. The N release rate from these amendments fell into four general groups: (1) rapid N release from soluble chemical fertilizer formulations, (2) longer, controlled N release from chemical‐based, slow‐release formulations, and a two‐phase release pattern (rapid initial phase, slower second phase) from (3) organic‐based blends, as well as (4) unsupplemented municipal yard‐waste composts. The release rates from organic‐based amendments were about three times faster in the 30°C laboratory incubations than in the cool, moist winter growing season at a field site in the Central Valley of California. Relative rates of N release can be compared between amendment materials to help guide selection of N amendments, according to the plant‐growth goals of the revegetation project. Copyright © 2006 John Wiley & Sons, Ltd.     

Potassium fertilization on sandy soils in relation to soil test,crop yield and K-leaching

To study the influence of potassium (K) fertilizer rate on soil test K values, crop yield, and K-leaching in sandy soils, four long-term fertilizer experiments (0–60–120–180 kg K ha^?1 a^?1) were initiated in 1988 in northern Germany on farmers fields. Clay content of the plow layer was about 4%, and organic matter between 2% and 5%. Plant available soil K was estimated with the double lactate (DL) method. Small grain cereals (rye and barley) did not respond to K fertilization in the 7-year period even though the soil test value of the K-0 plots decreased from ca. 90 to ca. 30 mg K_DL kg^?1 within 3 years. This value remained almost constant thereafter. Crop removal (including straw) of 75 kg K ha^?1 a^?1 was therefore apparently supplied from nonexchangeable K fractions. Compared to the optimum, no K application reduced the yield of potato by up to 21%, and that of white sugar yield up to 10%. Maximum potato yield was obtained by annually applying 60 kg K ha^?1 which resulted in a test value of 60 mg K_DL kg^?1 soil. Maximum potato yield was also obtained at 40 mg K_DL kg^?1 soil, however, with a single application of 200 kg K ha^?1. Similar results were obtained with sugar beet. This indicates that for maximum yield, even for K demanding crops, it is not necessary to maintain K_DL values above 40 mg K kg^?1 soil throughout the entire crop rotation. Soil test values increased roughly proportional to the K fertilizer level. About 120 kg fertilizer K ha^?1 a^?1, markedly more than crop K removal, was required to maintain the initial K_DL of 90 mg kg^?1. The K concentration of the soil solution in the top soil measured after harvest was increased exponentially by K fertilizer level and so was K leaching from the plow layer into the rooted subsoil. The leached quantity increased from 22 kg K ha_?1 a_?1 in the plot without K application to 42.79 and 133 kg Kha^?1 a^?1 in plots supplied with 60, 120 and 180 kg K ha^?1 a^?1 respectively. Soil test values around 100 mg K_DL kg^?1 on sandy soils, as often found in the plow layer of farmers fields, lead to K leaching below the root zone that may exceed the critical K concentration of 12 mg K T^?1 for drinking water.     

Competing land use in the reserve site selection problem

The objective of this paper is to present an approach that addresses competing land uses in the reserve site selection problem. This approach is implemented in a spatial optimization model for conservation planning in human-dominated landscapes: MENTOR. This model allocates new sites as stepping stones between existing sites. We illustrated the model by a case with competition for space between wildlife habitat and agriculture as it occurs in the Netherlands. We focused on deciduous forests with the European nuthatch Sitta europaea as an umbrella species for forest birds. Suitability maps for deciduous forests and for agriculture were applied as input for the allocation model.Effects on the landscape pattern, nuthatch populations, bird species richness and dairy farming were described. We can conclude that the application of MENTOR leads to an effective reserve network in De Leijen concerning the suitability of the land for dairy farming. The results show a doubling of the average proportion of occupied habitat, an increase in colonization probability of patches, a decrease in extinction probability of local populations, and an increase in bird species richness per patch. Whereas it results in a relatively small reduction in land currently used by agriculture.     

Livestock disease threats associated with intensification of pastoral dairy farming

This paper provides an overview of the changes in the pasture-based dairy systems of New Zealand and Australia that may influence the health of cattle.

There are relatively few available data that can be used to quantify the effects of increased intensification of milk production on the health of cattle. There is evidence that increased production increases the risk of mastitis and culling for udder health. Increased risks of mastitis with treatment with somatotropin support these findings; however, the risk of mastitis may decrease with increased milking frequency. Larger herds with greater stocking density should increase the risk for infectious disease, but evidence to support this contention is sparse.

Very intensive grazing patterns associated with higher grass yields achieved using better cultivars and greater use of fertilisers favour nematode parasites. There is some evidence of anthelmintic resistance in both nematodes and liver fluke. Veterinarians will need to be aware of the potential for these to reduce the productivity of cattle.

There have been benefits of improved nutrition on the efficiency of energy use for dairy production. Diseases such as bloat and ketosis appear to be of lower prevalence. It also appears that mineral nutrition of pasture-fed cattle is being better addressed, with gains in the control of milk fever, hypomagnesaemia and trace-element deficiencies. However, acidosis is a condition with a high point prevalence in pasture-based dairy systems where cows are fed supplements; one study in Australia found a point prevalence of approximately 11% of cows with acidosis. There is evidence from this study that the neutral detergent fibre (NDF) in pasture-based diets may need to be higher than 30% of the diet to maintain rumen stability. Laminitis and acidosis are different conditions with a similar pathogenesis, specifically highly fermentable diets. The prevalence of lameness was 28% in herds in Australia, suggesting that this condition must be a focus for preventive medical approaches, including the design of laneways, feedpads and dairies.     

Administration of Thyroxine Affects the Morphometric Parameters and VEGF Expression in the Uterus and Placenta and the Uterine Vascularization but does Not Affect Reproductive Parameters in Gilts During Early Gestation

The aim of this study was to evaluate the effects of thyroxine administration on morphometric parameters, expression of vascular endothelial growth factor (VEGF) and vascularization in the uterus and placenta and reproductive parameters in gilts at 70 days of gestation. At 150 days of age, i.e., before first heat, 20 gilts were randomly divided into two experimental groups: treated (n = 10) and control (n = 10). The treated group received a daily dose of 400 μg of l ‐thyroxine (T₄) in their diet until slaughter and the control group received only typical meals. Before artificial insemination, blood was collected to determine plasma total T₄. The gilts were inseminated in the second oestrus and slaughtered at 70 days of gestation. The foetal thyroid follicular epithelium height, number, size and weight of foetuses; foetal myogenesis, corpora lutea number, embryonic mortality rate, uterine weight, placental weight and placental fluid volume were measured. Histomorphometric and immunohistochemical analysis of uterus and placenta were determined. The averages of all variables were compared by the Student’s t‐test. The gilts treated with thyroxine showed significant increase of plasma total T₄. At 70 days of gestation, the heights of the trophoblastic epithelium, endometrial epithelium and endometrial gland epithelium were significantly higher in the group treated with T₄. The expression of cytoplasmatic and nuclear VEGF in trophoblastic cells and the number of blood vessels per field in endometrial stroma were significantly higher in the gilts treated with T₄. No other significant differences between groups were obtained with respect to other parameters (p > 0.05). We conclude that oral administration of T₄ up to 70 days of pregnancy in gilts affects the morphometric parameters, the expression of placental VEGF and the uterine vascularization but does not affect reproductive parameters in gilts during early gestation.     

A single vaccination of commercial broilers does not reduce transmission of H5N1 highly pathogenic avian influenza

ABSTRACT: Vaccination of chickens has become routine practice in Asian countries in which H5N1 highly pathogenic avian influenza (HPAI) is endemically present. This mainly applies to layer and breeder flocks, but broilers are usually left unvaccinated. Here we investigate whether vaccination is able to reduce HPAI H5N1 virus transmission among broiler chickens. Four sets of experiments were carried out, each consisting of 22 replicate trials containing a pair of birds. Experiments 1-3 were carried out with four-week-old birds that were unvaccinated, and vaccinated at day 1 or at day 10 of age. Experiment 4 was carried out with unvaccinated day-old broiler chicks. One chicken in each trial was inoculated with H5N1 HPAI virus. One chicken in each trial was inoculated with virus. The course of the infection chain was monitored by serological analysis, and by virus isolation performed on tracheal and cloacal swabs. The analyses were based on a stochastic SEIR model using a Bayesian inferential framework. When inoculation was carried out at the 28th day of life, transmission was efficient in unvaccinated birds, and in birds vaccinated at first or tenth day of life. In these experiments estimates of the latent period (~1.0 day), infectious period (~3.3 days), and transmission rate parameter (~1.4 per day) were similar, as were estimates of the reproduction number (~4) and generation interval (~1.4 day). Transmission was significantly less efficient in unvaccinated chickens when inoculation was carried out on the first day of life. These results show that vaccination of broiler chickens does not reduce transmission, and suggest that this may be due to the interference of maternal immunity.