Alan W. McKeown

Long-term marketable yields of horticultural crops in southern Ontario in relation to seasonal climate

In Ontario, Canada, marketable yields of certain annual horticultural crops increased steadily from 1940 to the mid-1980s, then dramatically decreased and became highly variable. This was not seen in field crops such as soybean and corn. Standard climatological variables showed little correlation with yields of vegetable crops such as tomatoes, cabbage, cauliflower, onions and rutabagas. The number of hot days (defined as days with maximum temperature greater than 30°C) and number of days with precipitation were better correlated with cool-season vegetable crop yield. With these climate measures we identified a period of milder growing season climate, from 1961 to 1986, and there was a greater frequency of hot days before and after this period. This analysis shows that horticultural crops are more sensitive to specific synoptic events, such as periods of hot days, than to overall growing season climate, and their yields may provide an indicator of a changing climate. Key words: Horticultural yields, histo...

Nitrogen and water requirements of fertigated cabbage in Ontario

Increasing nutrient and water regulations have necessitated development of best management practices for application of nitrogen (N) and water. This study was conducted to determine if there was an optimal balance of N and water applied for late storage cabbage (Brassica oleracea L. var. capitata). Five rates of N and five irrigation rates arranged in a response surface design replicated three times were supplied to Huron cabbage grown on sandy loam soil to study the interaction of N and water applied. Plots were located at the University of Guelph, Simcoe Research Station, Ontario, Canada from 2003 to 2005. Total and marketable yields were maximized from a low of 278 kg ha-1 N in 2005 to above the highest rate tested (400 kg ha-1 N) in the other 2 yr. In 2005, there were 29 d above 30 °C and marketable yield was 49% lower than 2004, which had only 1 d above 30 °C. A target soil water value of 100% of field capacity was required to maximize yield in all 3 yr. More N is required as the water supply increas...

Impact of high air temperatures on Brassicacae crops in southern Ontario

The yield patterns of many cool season vegetable crops were observed to be different from the gradual increase in yields that has been reported over time for corn and soybeans in Ontario. A study was conducted to determine if there was a relationship between yield and seasonal weather patterns for five vegetables (broccoli, cabbage, cauliflower, radish and rutabaga) in the family Brassicacae. The iterative chi-squared technique was used to identify correlations between daily temperature and marketable yield. Yields of all five of the crops showed some damage due to hot weather in August. For cauliflower, cabbage and rutabaga there was roughly a 10% yield loss for every 10 d that the temperature reached 30°C or above during the growing season. These results shed new insight into the mechanisms by which weather affects yield. Key words: Cabbage, broccoli, cauliflower, radish, rutabaga, yield, climate

Long-term evaluation of cover crop and strip-tillage on tomato yield, foliar diseases and nematode populations

A 6-yr (1987–1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT ...

Establishment of Critical Sap and Soil Nitrate Concentrations using a Cardy Nitrate Meter for Two Carrot Cultivars Grown on Organic and Mineral Soil

Abstract Nitrate (NO3 −) meters have been used effectively for crop nitrogen (N) management in many crops, including corn and cabbage. The use of a Cardy NO3 − meter to assess the N status of the carrot crop could improve the utilization of applied N, but critical NO3‐N concentrations are required. Two carrot cultivars were grown on mineral and organic soils over 3 years at five N application rates to establish critical sap and soil NO3‐N concentrations and to identify the effects of soil type and cultivar. Although a yield response to N application occurred on mineral soil in 2 of 3 years, consistent critical sap NO3‐N concentrations could not be established because of variability among years, cultivars, and soil types. Critical soil nitrate concentrations were highly variable, but values of 31 to 36 mg · L−1 NO3‐N could be established for the early sampling date to 30 cm deep. Sap NO3‐N concentrations cannot be used alone for N analysis of carrots, but early‐season soil NO3‐N assessment could be useful in adjusting N‐fertilization practices.

Nitrogen utilization timeline of carrot over the growing season

A timeline of nitrogen (N) dynamics of the carrot crop was developed based on studies on the effects of N application on carrot growth, N uptake and partitioning, and interactions with Alternaria [ALB; A. dauci (Kuhn) Groves and Skolko] and Cercospora [CLB; C. carotae (Pass.) Solheim] leaf blight. Preplant-applied fertilizer N affects yield only when residual N in the top 60 cm of the soil profile is insufficient. The majority of the N required by the crop is taken up beyond 50 d after seeding (DAS). Carrots have a root system that extends to 150-cm depth and >50% of the fibrous root system occurs below 30-cm depth. It is likely that N below 30 cm depth is required beyond 50 DAS, since the majority of the fibrous roots are below 30 cm depth after that stage. There is insufficient time for sidedressed N to leach into the active root system beyond 50 DAS, unless its application is timed before irrigation or rain events. Regardless of the amount of residual N, preplant-applied N is essential for minimizing l...

The effect of nitrogen on insect and disease pests of onions, carrots, and cabbage.

ABSTRACT Mineral nutrition may affect the ability of plants to resist harmful insects or diseases. The effects of nitrogen (N) nutrition on pests of onions (Allium cepa L.), carrots (Daucus carota L.), and cabbage (Brassica oleracea var. capitata L.) were evaluated on organic and mineral soils in Ontario, Canada in 2000 and 2001. Onions (cvs. Norstar and Winner) and carrots (cvs. Indiana, Idaho, and Annapolis) were grown on both soil types, and cabbage (cv. Atlantis) was grown on mineral soil. Nitrogen was applied at 0,50,100,150, and 200% (carrots and cabbage) and 0, 100, and 200% (onions) of the rate recommended by the Ontario Ministry of Agriculture, Food, and Rural Affairs using calcium ammonium nitrate preplant and potassium nitrate for sidedress applications. In cabbage, onion thrips (Thrips tabaci L.) damage was rated at harvest. Onion thrips (OT) populations were monitored in onions weekly. In carrots, the combined leaf blight symptoms caused by Cercospora carotae and Alternaria dauci was evaluated biweekly using a visual rating. The incidence and severity of cavity spot (Pythium spp.) was rated at harvest. The damage caused by OT was lower on cabbage that received 100–200% and 150% of the recommended N rate in 2000 and 2001, respectively, than the no N treatment in both years, and 200% of the recommended rate in 2001. This effect may have been due to delayed maturity of plants that received low and high N levels. Onion thrips populations in onions were not affected by N rate in either year or location. Leaf blight severity decreased with increasing N rate in most cases. There was no effect of N rate on cavity spot. Nitrogen management should be considered in the integrated pest/crop management program for cabbage, onions, and carrots.

Distribution of nitrogen uptake, fibrous roots and nitrogen in the soil profile for fresh-market and processing carrot cultivars

In temperate regions, yield of carrot [Daucus carota subsp. sativus (Hoffm.) Arkang.] is not generally affected by preplant applications of nitrogen (N). Previous studies speculate that carrots utilize N from much deeper in the soil profile than other crops. Carrot (cvs. Idaho and Fontana) were grown on organic and mineral soil in Ontario over a 3-yr period to determine rooting and N-uptake dynamics. Nitrogen application rates ranged from 0 to 200% of Ontario recommendations for each soil type. Soil samples collected at seeding and harvest at three depths were assessed for total N, nitrate-N and ammonium-N. The same cultivars were grown in 150-cm-deep PVC pipes filled with silica sand or soilless mix to assess root distribution and N uptake. Potassium nitrate fertilizer enriched with 15N was applied at three depths in the pipes and plants were assessed 28 d later for fertilizer N recovery. In the field, the highest N concentration both at seeding and at harvest was in the top 30 cm of the soil profile, bu...

The influence of nitrogen and calcium fertilizers on septoria late blight and yield of celery

Tesfaendrias, M. T., Trueman, C. L., Gossen, B. D., McKeown, A. W. and McDonald, M. R. 2014. The influence of nitrogen and calcium fertilizers on septoria late blight and yield of celery. Can. J. Plant Sci. 94: 1391-1399. Late blight (Septoria apiicola) reduces both yield and quality of fresh market and processing celery. Field trials were conducted over 4 site-years to evaluate the effect of nitrogen (N) rate and foliar calcium (Ca) fertilization on the development of late blight and yield on celery grown on muck soils, which have a high organic matter (OM) content. A treatment with the protectant fungicide chlorothalonil was included to determine if fertilizer could replace fungicide application in celery production. There was a cultivar×site-year interaction for each of the disease and yield variables. Repeated application of chlorothalonil fungicide reduced late blight and generally increased plant height, weight and marketable yield. The rate of N applied had a small effect on late blight, which varied among site-years. Area under the disease progress curve decreased with increasing rate of N at both sites in 2008. Similarly, an increasing rate of N resulted in an increase in yield in one of four site-years. Application of Ca did not affect late blight severity and increased yield in only 1 site-year. There was a negative correlation between late blight severity and yield. Tissue N concentrations varied among the treatments at sites with a relatively low OM content, but not at the high OM sites. The treatments had no effect on Ca tissue concentrations. Application of N and Ca alone did not adequately control late blight, but there was a slight reduction in late blight severity with increasing rates of N. Application of both N and Ca can improve yield and also contribute indirectly to improved late blight management in combination with fungicides and other integrated crop management practices.