On-farm Evaluation Research Articles

On‐farm evaluation of ridging and residue management options in a Sahelian millet‐cowpea intercrop. 1. Soil quality changes

Abstract. In the Sahel, promising technologies for agricultural intensification include millet stover mulching and ridging. A four year on‐farm experiment was set‐up in order to assess the effect of various combinations of these two technologies on soil chemical and physical quality in a millet (Pennisetum glaucum (L.) R. Br.) –‐ cowpea (Vigna unguiculata (L.) Walp.) relay intercropping system. Treatments included bare surface, ridging, a surface applied banded millet stover mulch (2 t ha–1) and a banded millet stover mulch (2 t ha–1) buried in ridges. The latter three treatments were implemented exclusively in the cowpea rows, with an annual rotation between the millet and cowpea rows. Both the bare and ridge plots experienced a rapid loss of organic carbon, acidification and the development of extensive surface crusts but no increase in bulk density or penetration resistance. In the year of application, mulching improved soil quality in the cowpea row with respect to pH, organic carbon and exchangeable K+ and Mg++ content, penetration resistance and bulk density, and it reduced the decline in exchangeable Ca++ and total N content. In the year following mulch application, a general decline in soil chemical quality was observed in the millet row, except for organic carbon content, and a positive residual effect was observed on penetration resistance and bulk density. As a rule, the effects of mulching in the year of application tended to be stronger in the ridged treatment with buried residue than in the banded surface mulch. In the year following application, this tendency was reversed. For the purpose of reducing soil degradation by nutrient mining and wind erosion, a banded surface mulch therefore appeared more effective than buried mulch.

On-farm evaluation of ridging and residue management options in a Sahelian millet-cowpea intercrop. 1. Soil quality changes

On-farm evaluation of ridging and residue management options in a Sahelian millet-cowpea intercrop. 1. Soil quality changes

ON-FARM COMPARISON OF FEEDING STRATEGIES BASED ON FORAGES FOR SMALL-SCALE DAIRY PRODUCTION SYSTEMS IN THE HIGHLANDS OF CENTRAL MEXICO

The on-farm evaluation of three feeding strategies for smallholder campesino dairy herds was undertaken in the highlands of Central Mexico with cooperating farmers: traditional, alternative and intermediate feeding strategies. All three incorporated grazing of cultivated pastures, but concentrate use was 4.0 and 7.0 kg per cow per day in the rainy and dry seasons respectively for the traditional feeding strategy, 3.3 for the alternative feeding strategy in both rainy and dry seasons and 5.0 and 9.0 kg per cow per day in the rainy and dry seasons respectively for the intermediate feeding strategy. Feeding during the dry season was based on maize straw in the traditional strategy, on pasture complemented with maize silage in the alternative feeding strategy, and with some maize silage but mostly maize straw in the intermediate feeding strategy. The trial ran between 25 September 1996 and 24 September 1997, divided by season into four, thirteen-week periods. Milk yields were recorded once per week, and live weight and body-condition score, every 28 days. Three cows per strategy that completed each period were blocked according to stage of lactation and used for the statistical analysis of a split-plot design with feeding strategies as main plots and weeks as split-plots. Overall mean milk yields were 15.5±2.05, 13.4±2.43 and 12.4±2.37 kg milk per cow per day for alternative, intermediate and traditional feeding strategies respectively, with significant interactions (P<0.05) for autumn, winter and summer. The alternative feeding strategy (with over 50% less concentrate) produced milk yields 0.24 and 0.38 higher than the intermediate and traditional feeding strategies in the dry season. In the rainy season, milk yields with the alternative feeding strategy (30% less concentrates) were 0.09 and 0.16 higher than the other two strategies. Margins per day of family labour were: alternative feeding strategy US$36.48 per day, intermediate feeding strategy US$9.22 per day and the traditional feeding strategy US$9.11 per day, although in the case of the last two there were two family members in charge of the dairy herds. Results demonstrate the successful integration of grazed pasture and maize silage for the efficient production of milk, and provide evidence on the productive use of limited campesino land resources in the face of unviable economic conditions for maize grain production.

Agriculture Intensification and Ecologically Sustainable Land Use in Niger: A Case Study of Evolution of Intensive Systems with Supplementary Irrigation

ABSTRACT In Niger, a breakdown of the bush-fallow system, low crop yields and reduced availability of communal land have resulted from increasing population pressure. Agricultural intensification is critical to the future development of the region. Intensification of agricultural production in Niger must include adoption of sustainable yield increasing technologies, fertilizer use, supplementary irrigation and/or water conservation, high yielding cultivars and improved crop management practices. On-farm constraints analysis of crop productivity and technologies assessment was carried out in two irrigated perimeters: the Konni surface irrigation and the Djirataoua deep well system where supplemental irrigation is provided to rainy season crops in the event of long dry spells, and full irrigation is supplied to dry season crops. Konni is located in southern Niger, approximately 13°48'0′N, 5°15'0′E at approximately 257 m altitude; Djirataoua is located further east, approximately 13°20'0′N, 7°7'60′E at approximately 368 m altitude, near Maradi, which is located at approximately 13°28°60′N, 7°5′60E, approximately 376 m altitude. In both the Konni and Djirataoua irrigation systems, use of supplementary irrigation has enhanced cropping intensity and crop productivity per unit area (yield) while generating greater employment opportunity. Analysis of long-term crop productivity trends during 1980–1997 revealed that sustainability of gained productivity is possible through agricultural intensification over years without any sign of productivity decline. These results show that the use of agriculture intensification technologies plays a crucial role in sustainable, increased crop production in the Sahel. The results of our diagnostic survey in these two perimeters showed that the major constraints to increased productivity are low fertilizer use, poor nutrient use efficiency, the lack of well adapted, high yielding varieties or hybrids, poor crop establishment and plant protection in farmers fields, and inappropriate input and output pricing. On-farm evaluation of the improved technologies, namely improved varieties or hybrids and optimal fertilizer use with optimal supplementary irrigation, resulted in a 35% increase in grain yields at the farm level. The lesson learned from this study is that developing sustainable agricultural production systems in Niger with higher yields, or production per unit area, than present-day yields depends upon supplementary irrigation if or where potential exists, and upon promotion of fertilizer use, high yielding cultivars and other innovative production technologies. This strategy will help reduce frequency and intensity of food shortages and will ultimately help reduce the incidence of poverty and starvation in Niger.

On-Farm Testing of the pnutGRO Crop Growth Model in Florida1

Abstract pnutGRO is a peanut crop growth simulation model which calculates crop carbon, nitrogen and water balances at the process level. An on-farm evaluation of pnutGRO v1.02 was conducted at 15 field sites in two Florida counties during the 1990 and 1991 cropping seasons. Independent crop and soil data sets were collected to evaluate pnutGRO simulations. The accuracy of the pnutGRO simulations was affected by year and location. Sites where peanut (Arachis hypogaea L.) was grown in rotations following bahiagrass (Paspalum notatum Fleuge) (Levy County, 1990) had low disease pressure, high pod yields (5260 kg/ha), and the best model fit (pnutGRO simulations were within 9% of observed yield data). Sites where peanut followed other row crops often showed high infestation levels of root-knot nematode [Meloidogyne arenaria (Neal) Chitwood] or stem rot (Sclerotium rolfsii Sacc.) (Jackson County, 1991). This resulted in reduced pod yields (3260 kg/ha) and poorer model fit (pnutGRO simulations were 44% above observed yields). pnutGRO correctly predicted relative yield decreases due to drought. Overall, pnutGRO v1.02 appears to be most useful as a predictor of optimal peanut yield for specific cultivars under given soil and weather conditions. Inclusion of pest and disease damage functions would improve model accuracy for farms where biotic stress reduces potential peanut yield.

On-Farm Evaluation of Indian Major Carp Production with Sugarcane Bagasse as Substrate for Periphyton

To study the effect of sugarcane bagasse as an artificial substrate for periphyton in fish ponds, an on-farm polyculture experiment was carried out, stocking catla (Catla catla), rohu (Labeo rohita) and common carp (Cyprinus carpio) in an 800 m2 earthen pond partitioned into eight 100 m2 compartments with fine meshed nylon netting. Fifty catla and 25 each of common carp and rohu were stocked per compartment and grown for 180 days. Sugarcane bagasse bundles (length 80 cm, diameter 3.3 cm) at densities of 0, 39, 78 and 156 (or 0, 7.0, 13.7 and 28.2 kg 100 m-2) were hung in two compartments each as a substrate. Supplemental feed (a 1:1mixture of groundnut cake and rice bran) was provided in one replicate of each substrate density at a rate of 5% body weight during the first half and 3% throughout the second half of the experiment. Water quality and periphyton biomass were monitored at fortnightly and monthly intervals, respectively. Bagasse substrate did not adversely affect water quality, dissolved oxygen levels being between 4 and 13 mg·l-1 throughout the experiment. Only minor differences in periphyton and plankton density were observed between treatments. Marked differences were recorded in fish production. Total fish production of 8076 g·100 m-2 was obtained without feed and periphyton (control). Feeding alone increased yield compared to controls by 20%. Bagasse substrate alone increased yields by 38, 61 and 62% in the 39, 78 and 156 bagasse bundles per 100 m-2 treatments, respectively, while the combination of feeding and periphyton resulted in 45, 67 and 84% increases in yield in the 39, 78 and 156 bagasse Asian Fisheries Science 14(2001): 367-376 Asian Fisheries Society, Manila, Philippines *Corresponding author

Crop demand-driven site-specific nitrogen applications in rice (Oryza sativa) and wheat (Triticum aestivum): some recent advances

Management of fertilizer nitrogen in rice (Oryza sativa L.) and wheat (Triticum aestivum L. emend. Fiori & Paol.) in India typically consists of blanket recommendations, developed for large tracts having similar climate and land forms. It cannot help the increase N-use efficiency beyond a limit. Further improvement can be achieved only by planning strategies for fertilizer N management responsive to temporal variations in crop N demand and fieldiito- field variability in soil-N supply. Improvement in the synchrony between crop N demand and the N supply from soil or the applied N fertilizer is likely to be the most promising strategy to improve N-use efficiency. It can be achieved by following real-time N management based on periodic assessment of plant-N status and delayed application of fertilizer N until the N level goes below a critical level. Gadgets like chlorophyll-meter (SPAD-meter) and inexpen- sive leaf colour chart (LCC) have proved quick and reliable tools to decide the time when fertilizer N needs to be applied to the crop. Recently significant progress has been made in the development and on-farm evaluation of LCC-based real-time N management in rice, but there is a need to work out appropriate criteria for using need- based N-management strategy in wheat. Optical sensors offer an opportunity to take into account both plant N sta- tus (or leaf colour) as well as crop biomass for making crop-demand-driven fertilizer-N recommendations. Combi- nation of preventive location-specific split schedule with corrective LCC or SDAD-meter or optical sensor-based N management constitutes another attractive strategy for achieving high N-use efficiency in rice and wheat. The fixed-time or adjustable-dose approach seems very promising for wheat, because unlike in rice, the fertilizer appli- cations need to be synchronized with irrigation events. Appropriate preventive fertilizer-N management scenarios need to be worked out that can be used before using the SPAD meter, LCC or optical sensors to guide corrective fertilizer-N application at a given crop-growth stage.

A sampling method for estimating the accuracy of predicted breeding values in genetic evaluation

A sampling-based method for estimating the accuracy of estimated breeding values using an animal model is presented. Empirical variances of true and estimated breeding values were estimated from a simulated n-sample. The method was validated using a small data set from the Parthenaise breed with the estimated coefficient of determination converging to the true values. It was applied to the French Salers data file used for the 2000 on-farm evaluation (IBOVAL) of muscle development score. A drawback of the method is its computational demand. Consequently, convergence can not be achieved in a reasonable time for very large data files. Two advantages of the method are that a) it is applicable to any model (animal, sire, multivariate, maternal effects...) and b) it supplies off-diagonal coefficients of the inverse of the mixed model equations and can therefore be the basis of connectedness studies.

Participatory on-farm evaluation of the response to concentrate supplementation by cows in early lactation in smallholder peasant (campesino) dairy production systems in the highlands of central Mexico

Concentrates are the main cash expenditure in smallholder campesino dairying in the highlands of Central Mexico. Improved, low-cost, appropriate feeding strategies have been therefore identified by campesinos as a priority. An on-farm trial was undertaken in 1998 to evaluate the response to supplementation with concentrates by dairy cows in early lactation during the rainy season with restricted access to grazing of ryegrass/white clover pastures. A base of 3·0 kg commercial concentrate/cow/day (S3) was compared against the higher rate used by farmers of 5·0 kg/cow/day (S5). Three farmers with one, and one farmer with two pairs of freshly calved upgraded Holstein cows participated in the trial (24±10·7 days into lactation). Data were analysed by a random block split-plot design where supplementation treatments were main plots and measurement periods were split-plots. Milk yield was recorded once per week for 9 weeks, and live weight and condition score for four 28 day periods. Milk yields were 21·8 for S3 and 21·9 for S5 (±0·714) kg milk/day/cow (P > 0·05); live weight S3 = 444·0 and S5 = 496·0 (±12·663) kg/cow (P > 0·05), and condition score S3 = 1·9, and S5 = 1·8 (±1·127) (P >0·05). There were no significant (P> 0·05) effects of measurement periods, and there was no significant (P > 0·05) interaction. The lack of response in milk yield, live weight or condition score to increased concentrate supplementation demonstrates that at these levels of production and management, the access to grazing of improved pastures, plus limited concentrate, enables cows in campesino systems to meet their nutrient requirements, and the feasibility of efficient milk production from grazed pastures as an appropriate technology. It is also concluded that it is an appropriate technology and that the results have implications for research and extension workers in rural development who have promoted large amounts of concentrate to dairy cows as the only way towards high yields and efficient milk production.

A comparison of formal and participatory breeding approaches using selection theory

Progress from plant breeding has been slow in some marginal environments. Conventional or formal plant breeding (FPB) programs conducted by international agricultural research centres or national programs in developing countries have been criticized for ignoring indigenous germplasm, failing to breed for conditions facing poor farmers, and emphasizing selection for broad versus local adaptation. A suite of techniques, referred to as participatory plant breeding (PPB) and including farmer-participatory or farmer-led selection, on-farm evaluation, and use of local landraces, has been advocated in response to this critique. PPB programs are diverse in scope and approach, but often rely heavily on farmer visual evaluation or phenotypic mass selection to select for simply-inherited traits, with limited replicated yield testing in multiple-environment trials (MET), one of the main tools of FPB. Prediction equations derived from selection theory can be used to examine the conditions under which idealized versions of FPB and PPB may be expected to achieve genetic progress for traits such as yield. The effectiveness of any selection environment is determined by both the genetic correlation between genotype performance in it and the target environment (r G) and the heritability of genotypic differences in the selection environment (H s). r is a measure of the accuracy with which performance of genotypes in the selection environment predicts performance in the target environment; H s is a measure of the precision with which performance differences among genotypes can be measured in the selection environment. We compare FPB and PPB with respect to these determinants of selection response, using examples from self-pollinated species. Particular areas examined include: (i) selection for broad versus specific adaptation; (ii) on-station versus on-farm selection; and (iii) selection under high-yield versus low-yield conditions. In general, PPB systems attempt to maximize gains through the use of on-farm evaluation and the skills of farmer-selectors to maximize r G. FPB exploits METs to maximize H s. PPB is most likely to develop cultivars that out-perform the products of FPB when it is applied in low-yield cropping systems, because it is in such situations that r G between high-yield breeding nurseries and low-yield target environments is likely to be low or negative. To make continued gains, and to compete with internationally-supported FPB programs, PPB systems will need to counter the obscuring effects of uncontrollable within-field, site-to-site, and year-to-year heterogeneity. Simple and robust designs for on-farm METs are needed for this purpose.

On-farm evaluation of the establishment of clonal rubber in multistrata agroforests in Jambi, Indonesia

Perennial tree crops are often grown in complex multistrata systems that incorporate natural vegetation. These systems contribute simultaneously to sustaining rural livelihoods and to the conservation of biodiversity, but their productivity is usually low. Introduction of high yielding germplasm, usually selected in monocultural plantations, is a potential way to increase productivity, but a critical requirement is that such plants can be established in a competitive multispecies environment. The establishment of clonal planting stock in the jungle rubber agroforests of Indonesia was explored through participatory on-farm research. The trial involved four farmers who grew clonal rubber trees in a total of 20 plots, constituting five replicate experimental blocks spread across four farms. Unexpectedly, vertebrate pest damage by monkeys (Presbytis melalophos nobilis) and wild pigs (Sus scrofa) was the most important influence on establishment, explaining almost 70% of the variation in rubber tree growth. The amount of labour invested in weeding was also positively correlated with rubber tree growth. Farmers generally decided to completely cut back vegetation between rows of rubber trees, including potentially valuable trees, rather than weeding within the rows and selectively pruning trees in the inter-row. Farmers thought that the inter-row vegetation would harbour vertebrate pests and compete with the clonal rubber, and they had access to fruits, firewood and other non-timber forest products from other land. Thus, contrary to expectations, when offered clonal germplasm, farmers opted to use plantation monoculture methods to protect what they considered a valuable asset, rather than maintain the traditional multispecies strategy they use with local germplasm.

Efficacy of sperm mobility assessment in commercial flocks and the relationships of sperm mobility and insemination dose with fertility in turkeys

Our objectives were to evaluate: 1) the efficacy of the Sperm Mobility Test on commercial turkey farms, and 2) the influence of sperm mobility phenotype on fertility when insemination parameters are varied. In research flocks, differences in sperm mobility among toms are predictive of fertility. We wanted to test the efficacy of this sire selection test in practical, real-world situations, evaluating its usefulness in terms of assessing large numbers of toms, different strains of turkeys, and variable management practices. Utilizing field study results, controlled studies were then conducted to improve test parameters. For the field trials, semen from each of 405 breeder toms (11 strains or lines) was evaluated either in duplicate (n = 285) or in triplicate (n = 120). Sperm mobility was normally distributed among all toms tested, except for one strain. Because the sperm mobility indices for toms evaluated in these field trials were higher than those observed in research flocks, the Sperm Mobility Test was modified to increase the separation between high and low sperm mobility phenotypes by increasing the concentration of Accudenz. To determine the effects of sperm mobility and insemination dose on sustained fertility through time, hens from a research flock were inseminated twice before the onset of lay with sperm from toms classified as high-, average-, or low-mobility in concentrations of 25 to 400 million sperm per artificial insemination dose, and egg fertility was evaluated over a 5-wk period. Toms with the high-mobility sperm phenotype maintained higher fertility (P < 0.05) over the 5-wk period at all insemination doses compared with toms with low-mobility sperm. Toms with high-mobility sperm sired equal numbers of poults in a sperm competition study in which numbers favored low-mobility toms by 3:1. These results demonstrate that the Sperm Mobility Test can be used for on-farm evaluation of semen quality of toms in commercial flocks and that sperm mobility influences fertility and sire fitness.

On-farm evaluation of cobalt/vitamin B12 supplementation for lamb growth on southern South Island properties

On-farm cobalt/vitamin B12 supplementation trials were carried out with 3-month-old weaned lambs (N = 50) on six southern South Island properties that were considered to be deficient or marginal for cobalt over the years 1996-1999. No significant liveweight responses of the lambs were recorded over a 3-month period on any of the farms in any year. When lambs were raised on cobalt-treated pasture and were injected with vitamin B12 or had rumen cobalt pellets administered, liver and serum vitamin B12 concentrations increased. Plot trials showed two light sprays of cobalt sulphate at 60 g/ ha, 2 months apart over summer, was an effective means of maintaining herbage concentrations in the desirable range, i.e., &gt;0.1 mg Co/kg DM. Monitoring of herbage cobalt and tissue vitamin B12 concentrations of animals was essential to indicate when lambs may need cobalt or vitamin B12 supplementation. Current reference values over-estimated the probability of responses in this set of experiments. Keywords: Cobalt, cobalt herbage level, lamb growth, vitamin B12

A Bio-Economic On-Farm Evaluation of the Use of Sweet Potato for Complementary Weed Control in a Yam/Maize/Egusi/Cassava Intercrop in Pigeon Pea Hedgerows in the Rain Forest Belt of Nigeria

ABSTRACT The bio-economic on-farm evaluation was conducted on resource-poor farmers' farms in the Orlu and Owerri Agricultural Zones in the rain forest belt of Nigeria in 1996 and 1997. It estimated the difference in profit or loss expected from the introduction of sweet potato at 6, 8 and 10 weeks after planting (WAP) as a complementary weed control measure to egusi in a yam/maize/egusi/cassava intercrop against the practice of two hand weedings (4 and 12 WAP). A randomized complete block design with five replications and forty farmers was used. Analysis of variance was used to assess the biological yields and partial budgeting used for the economic analysis while farmers' potential acceptability or rejection of the intervention was assessed by means of simple direct survey. The prevalent grass weeds were suppressed by the egusi and sweet potato although they later reappeared sparsely. The egusi acted as the early weed suppressant during the initial growth of the component crops. The sweet potato continued the ground cover provided by the egusi at different degrees. The yields of all the component crops except cassava were statistically similar. The yield of yam and cassava was higher where sweet potato was introduced at 10 WAP (9.4% and 7.6%, respectively) than with two hand weedings. It has both the highest combined monetary value of all the component crops (N234,752) and net benefit (N228,702). There were savings in labour in the use of the intervention and it offers an opportunity that can reduce production cost and drudgery.

On-farm evaluation of measures to monitor and control soybean pod-borer Etiella zinckenella in East Java, Indonesia

The incidence levels of moths and larvae of Etiella zinckenella were studied in the reproductive stage of soybean at eight farmers' field sites. A positive relationship was found between moths, caught by sweeping during flowering and pod-formation, and seed damage. Hence, rough predictions of damage can be made based on moth catches. Damage incidence was recorded in unsprayed plots and in plots sprayed with deltamethrin during flowering and pod-formation. Spraying did not affect the densities of moths and larvae or damage to pods and seeds. Larvae of H. armigera, Spodoptera litura and Plusiinae were not affected by spraying, but the pod-sucking bug Riptorus linearis, and two groups of predators, spiders and coccinellids, were reduced.

On-farm evaluation of chlorophyll meter-based N management in irrigated transplanted rice in the Cauvery Delta, Tamil Nadu, India

On-farm evaluation of chlorophyll meter-based N management in irrigated transplanted rice in the Cauvery Delta, Tamil Nadu, India

EFFECT OF CONTROLLED DRAINAGE AND SUBIRRIGATION ON SUBSURFACE TILE DRAINAGE NITRATE LOSS AND CROP YIELD AT THE FARM SCALE

An on-farm evaluation of controlled drainage and subirrigation systems can raise farmer awareness and acceptance of these innovative technologies. A four hectare field experiment was established on sandy-loam soil near Harrow in Essex County, Ontario. The field was modified to allow the implementation of two water table-management treatments, controlled drainage with subirrigation (CDS) and free outlet tile drainage (DR). Volume of tile drainage, nitrate concentration and loss in the tile drainage water and crop yields were measured. The objectives of the study were to provide on-farm demonstrations of controlled drainage and subirrigation systems, and to determine their effect on crop yields and environmental benefits.The CDS system reduced flow weighted mean nitrate concentration in tile drainage water by 38% and total nitrate loss by 37% compared to the DR system from May 1995 to April 1997. The CDS system increased marketable tomato yields by 11% in 1995. The average marketable tomato yields were 58.4 t ha−1 for DR system and 64.9 t h−1 for CDS system. The CDS system also increased corn yields by 64% in 1996. The average corn yields were 6.7 t ha−1 for DR system and 11.0 t ha−1 for CDS system. Thus, the CDS system effectively reduced total nitrate loss and improved yields of both processing tomatoes and grain corn on a sandy loam soil.

A Veterinary Perspective of On-Farm Evaluation of Nutrition and Reproduction

Reproductive herd health programs of the 1960s and 1970s focused primarily on the control of infectious and noninfectious diseases of the reproductive tract, estrus detection, breeding technique, semen quality and handling, and endocrine imbalances. Despite veterinary intervention, conception rates dropped from 55% before this period to 45% after this period, but milk production increased greatly.Because studies have shown that the additional nutritional needs for high producing cows may be a factor limiting reproduction, bovine practitioners have become more involved with dairy nutrition. New emphasis has been placed on the concept of total production medicine with the anticipation that improved nutrition would improve reproduction. Because of a better understanding of the dynamics of energy in the dairy cow and its effect on reproduction, fertility examinations now include nutrition monitoring and body condition scoring.Several relationships between nutrition and fertility have been identified: high producing thin cows that drop 0.75 to 1.0 in body condition score resulting in anestrus; fat dry cows that develop fatty livers and associated postpartum disease; heifers that have good milk production but prolonged anestrus; dry cows with ration imbalances during the transition period that develop milk fever, retained placenta, displaced abomasum, metritis, or endometritis; lactating cows with disease in midlactation, especially feet and leg problems, resulting in lowered fertility; and healthy, lactating cows with poor conception that have high concentrations of urea N in blood or milk.

On-farm evaluation of an animal-drawn implement developed in Ethiopia for row placement of wheat seed and basal fertiliser

Grass weeds are difficult to control by hand weeding in a broadcast wheat crop because several species are not easily distinguished from the crop at an early stage. Chemical weed control, on the other hand, can be highly effective, but is limited in Ethiopia by the unavailability and high cost of herbicides. Further, dependence on high efficacy herbicides to control grass weeds can result in weed species shifts and/or the development of resistant weed biotypes. Row sowing of wheat can facilitate hand and/or mechanical weeding by enabling farmers to identify grass weeds in the inter-row spaces. However, manual row seeding is extremely labour intensive and unacceptable to peasant farmers in Ethiopia. Row seeders developed elsewhere have not been accepted in Ethiopia because they were either too labour inefficient or ineffective in cloddy and rough fields. Therefore, a four-row seeder has been developed in Ethiopia with a new type of seed metering mechanism. Field tests have shown that the row seeder can work effectively in fields prepared by ox plough. The row seeder is labour efficient, requiring less than 25% of the time per unit area compared to the farmers' conventional practice of broadcasting seed and fertilizer and covering by ox plough. The seeder also facilitates placement of seed and fertilizer together in the row, enabling the crop to utilise fertiliser more effectively and limiting the nutrients available to weeds emerging between crop rows. In one season, use of the row seeder increased wheat grain yield by 28% in comparison to the conventional broadcasting. The row seeder used in conjunction with an inter-row weeder was the most profitable package tested on farmers' fields in 1995 and 1996, representing a sustainable production technology for peasant wheat farmers in Ethiopia.

Erosion effects on soil properties and soybean yield of a Miamian soil in Western Ohio in a season with below normal rainfall

Accelerated erosion can have adverse effects on soil properties and crop yield. Therefore, an onfarm evaluation of the effects of past soil erosion on productivity was done for a Miamian soil (fine, mixed, mesic Typic Hapludalfs) in central Ohio in 1991. Three levels of soil erosion identified by a field survey and topsoil depth included slight (20–25 cm topsoil depth), moderate (15–20 cm) and severe erosion (10–15 cm). Soybean yield and soil properties under these conditions were compared with those for uneroded soil (wooded conditions with topsoil of 25–30 cm depth) and for deposition sites (30–35 cm depth). Soil properties measured included bulk density, particle density, organic carbon contents, infiltration capacity, and moisture retention at different suctions. Bulk density of 0 to 10 cm depth was significantly low in uneroded control (1.20 Mg/m 3). High bulk density of 1.45 to 1.49 Mg/m 3 was observed in moderately and severely eroded phases. The moisture retention at 0.03 MPa (0.47 V V ) was the highest in uneroded control. The highest available water capacity of the 0 to 10 cm layer (0.16 to 0.17 V V ) was observed for wooded control and slight erosion phase. Total aggregation was also the least on slightly eroded phase. Soil organic carbon content did not differ among three erosional phases with a 0 to 10 cm depth mean value of 1.03% compared with 1.83% for deposition and 2.93% for wooded soils. Similar trends were observed for the 10 to 20 cm depth. Concentrations of exchangeable K, Ca, and Mg and total CEC increased with increasing degree of erosion for both depths. There were no differences in CEC of the 0 to 10 cm depth for severely eroded and wooded soils. The rainfall received during 1991 was below normal. There were no differences in soybean yield among slight, moderate and severely eroded phases. Because of severe crusting and drought stress, crop stand was poor on slightly eroded plateau soils. Adverse soil physical conditions, low soil organic carbon content, severe crusting, and drought were likely responsible factors for low yields on slightly eroded plateau soils. Soybean grain yield was 1.5 Mg/ha for slight erosion, 1.4 Mg/ha for moderate erosion, 1.6 Mg/ha for severe erosion, and 3.1 Mg/ha for deposition soil. There were no differences in grain yield or biomass production among slight, moderate or severe eroded phases. The highest yields of soybean obtained on deposition sites were attributed to the favorable soil moisture regime during this unusually dry growing season of 1991 in central Ohio.