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- Author or Editor: A. Abdul-Baki x
Intensive rainfall during summer causes substantial nutrient leaching in a subtropical region, where most vegetable lands lay fallow during this period. Also, an excessive amount of irrigation water supplied during the winter vegetable growing season leads to soil nutrient loss, which greatly impacts vegetable yields, especially in soils that possess a low capacity to retain soil water and nutrients. A 2-year field experiment was carried out to evaluate the effects of various summer cover crops and irrigation rates on tomato yields and quality, and on soil fertility in a subtropical region of Florida. The cover crops were sunn hemp [Crotalaria juncea (L.) `Tropic Sun'], cowpea [Vigna unguiculata (L.) Walp, `Iron Clay'], velvetbean [Mucuna deeringiana (Bort.) Merr.], and sorghum sudangrass [Sorghum bicolor × S. bicolor var. sudanense (Piper) Stapf.], with a weed-free fallow as a control. The cover crops were planted during late Spring 2001 and 2002, incorporated into the soil in the fall, and tomatoes [Lycopersicon esculentum (Mill.) `Sanibel'] were grown on raised beds during Winter 2001–02 and 2002–03, respectively. Irrigation in various treatments was controlled when tensiometer readings reached –5, –10, –20, or –30 kPa. The cover crops produced from 5.2 to 12.5 Mg·ha–1 of above ground dry biomass and 48 to 356 Mg·ha–1 of N during 2001–02 and from 3.6 to 9.7 Mg·ha–1 of dry biomass and 35 to 277 kg·ha–1 of N during 2002–03. The highest N contribution was made by sunn hemp and the lowest by sorghum sudangrass. Based on 2-year data, tomato marketable yields were increased from 14% to 27% (p ≤ 0.05) by growing cover crops, and the greatest increase occurred in the sunn hemp treatment followed by the cowpea treatment. Irrigation at –10, –20, and –30 kPa significantly improved marketable yields by 14%, 12%, and 25% (p ≤ 0.05) for 2001–02, and 18%, 31%, and 34% (p ≤ 0.05) for 2002–03, respectively, compared to yields at the commonly applied rate, –5 kPa (control). Irrigation at –30 kPa used about 85% less water than at –5 kPa. Yields of extra-large fruit in the sunn hemp and cowpea treatments from the first harvest in both years averaged 12.6 to 15.2 Mg·ha–1, and they were significantly higher than yields in the fallow treatment (10.2 to 11.3 Mg·ha–1). Likewise at –30 kPa yields of extra-large fruit from the first harvest for both years were 13.0 to 15.3 Mg·ha–1 compared to 9.8 to 10.7 Mg·ha–1 at –5 kPa. Soil NO3-N and total N contents in sunn hemp and cowpea treatments were significantly higher than those in fallow. The results indicate that growing legume summer cover crops in a subtropical region, especially sunn hemp and cowpea, and reducing irrigation rates are valuable approaches to conserve soil nutrients and water, and to improve soil fertility and tomato yields and quality.
A low-input sustainable agricultural system for the production of staked, fresh-market field tomatoes (Lycopersicon esculentum Mill.) is described. The system uses winter annual cover crops to fix N, recycle leftover nutrients, produce biomass, and prevent soil erosion throughout the winter and spring. Yields of tomato plants grown in hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) plus hairy vetch mulches were higher than those grown in the conventional black polyethylene (BP) mulch system in 2 of 3 years. Fruit were heavier with the plant mulches than with BP mulch. Eight weeks after transplanting, N levels in tomato leaves were higher with plant than with BP mulch, although the plant mulch plots received only 50% of the N applied to the BP plots. The cover crops had no effect on populations of five phytoparasitic nematode species.
Concern for the environment has focussed attention on the need for environmentally sound, yet economically profitable, farming practices. A hairy vetch (Vicia villosa L. Roth.) organic mulch system for fresh-market tomato (Lycopersicon esculentum Mill.) production provides environmental benefits by enhancing the soil and reducing the need for fertilizer and herbicide inputs and is more profitable than conventional practices. Tomato field trials over 3 years at the Beltsville (Md.) Agricultural Research Center compared the hairy vetch mulch system with black polyethylene mulch and bare ground (no mulch). Using partial budget analysis in a farm context, the hairy vetch mulch treatment was more profitable in all years under all market and yield adjustment scenarios. The vetch mulch system also was the preferred system for a risk-averse grower, according to a safety-first criterion. The combination of environmental benefits and the economic benefits to the grower make the hairy vetch mulch system an attractive alternative for producing fresh-market tomatoes in the Mid-Atlantic and parts of northeastern United States.
Prolific flowering is essential for economic seed production in sunn hemp (Crotalaria juncea L.). Since flowers appear as racimes on the distal portions of secondary branches and since the branching is restricted by a strong apical dominance, lifting the apical dominance by cutting the tops of plants should induce more branches and more flowers per plant. We evaluated this concept in a field experiment conducted in 1999 at the Tropical Research and Education Center, Univ. of Florida, Homestead, by cutting main stems of 100-day-old plants in a dense stand (113,000 plants/ha) at 30, 60, and 90 cm above the soil surface. Cutting at all heights induced more branching and flowering than the control. The highest positive response was in plants in which the main stem was cut at 90 cm above soil surface.
The mineral concentration of bearing `Mejhool' date palm (Phoenix dactylifera L.) trees was investigated with the objective of identifying the cause of browning and dieback of distal parts of the fruit-bearing strands. Tissue analyses of leaves, fruits, healthy and dead portions of fruit-bearing strands indicated that tissue browning and dieback appeared to be associated with a high concentration of certain mineral elements. A comparison of mineral concentration between healthy and dead tissue of the fruit-bearing strands showed no significant increase in K, Cu, B, Zn, and Na, but very high increases in the concentrations of P, Ca, Mg, S, Mn, and Fe. The levels of P, Ca, Mg, S, Mn, and Fe in the distal part of the fruit-bearing strand over a 3-year average were 5, 18, 12, 3, 11, and 2 times, respectively, higher than those in the healthy, proximal part of the strand. Mineral concentrations of leaves and mature fruits were determined for comparison with those in fruit-bearing strands.
Ten cultivars of processing tomatoes (Lycopersicon esculentum Mill.) grown in bare soil or on black polyethylene and hairy vetch (Vicia villosa Roth.) mulches were evaluated for yield, fruit processing quality, and leaf necrosis. Yields were higher, fruit was heavier, and leaf necrosis less in hairy vetch than in bare soil or black polyethylene mulch. With the exception of pH, yield and fruit quality component responses to mulch treatments were not cultivar-dependent. Fruit pH, soluble solids concentration, and color equaled values obtained using bare soil production practices. Percent solids was highest with black polyethylene and lowest in hairy vetch. The hairy vetch mulch delayed fruit maturity compared to the bare soil and black polyethylene. The hairy vetch cultural system has the potential to increase yield of processing tomatoes.