Woody Perennial Crops Research Articles

Weed management in short rotation poplar and herbaceous perennial crops grown for biofuel production

Weed management is a key element of any crop production system. Weeds are a particular problem in the production of short rotation woody and perennial herbaceous biomass crops due to the shortage of registered herbicides and integrated weed management systems. Herbicides will be an important component of weed management of biomass crops. However, producers should take a broader view of weeds and incorporate all available weed management tactics in these production systems. In both short rotation poplar and herbaceous perennial crops, weed control during the establishment period is most critical. New plantings of these species grow very slowly and do not compete well with weeds until a canopy develops. Effective weed control can double the growth of short rotation poplar crops and affect the variability of the resulting stand. In crops like switchgrass, uncontrolled weeds during establishment can result in stand failure. Cultural practices such as site preparation, using weed-free seed, fallowing, selecting the proper planting dates, companion crops and controlling weeds in previous crops must be combined with herbicides to develop integrated management systems. Weeds may also cause problems in established stands through competition with the biomass crop and by contaminating the product. Effective and economical weed management systems will be essential for the development of short rotation woody and herbaceous perennial biomass crop production systems.

Growth Inhibition of Ericaceous Plants from Metolachlor

Abstract Yellow nutsedge (Cyperus esculentus L.) is a major weed problem in many perennial woody crops. Dual 8E4 (metolachlor) at 4.5, 6.7, 9.0 and 13.5 kg/ha (4, 6, 8 and 12 lb/A) was evaluated in the field for 4 years to determine phytotoxicity to 11 varieties of azaleas. Also evaluated were Ericaceous species including coast leucothoe, compact Japanese andromeda, and Rhododendron × ‘PJM’. Fall or spring applications of metolachlor at rates up to 13.5 kg/ha (12.0 lb/A) caused no injury to the established azaleas ‘Delaware Valley White’, ‘Hershey Red’ and ‘Hinocrimson’. Some temporary injury occurred to newly planted ‘Hinocrimson’ azaleas treated with metolachlor at 6.7 kg/ha (6.0 lb/A). A July application at this same rate caused some temporary injury to established ‘Delaware Valley White’, ‘Double Pink’, ‘Hershey Red’, ‘Hot Shot’, ‘Karen’, ‘Lady Robin’, ‘Rosebud’ and ‘Tradition’ azaleas and ‘Coast lecothoe’ and ‘PJM’ rhododendron. No reduction in crop quality or size was observed with any species at time of crop harvest.

Citrus Mycorrhizae: Potential Benefits and Interactions with Pathogens

Abstract The capability of vesicular-arbuscular mycorrhizal (VAM) fungi, symbiotically associated with roots of citrus and most other woody perennial crops, to dramatically enhance plant growth has attracted widespread interest among horticulturists. Unfortunately, too often scientists engaging in mycorrhizal research have become overly enthusiastic with growth responses that were created under artificial experimental conditions. Mycorrhizae are the “normal” condition of roots on citrus trees and most other horticultural plants in the field (44). The nonmycorrhizal condition is “abnormal” and often the consequence of “normal” horticultural practices, such as overuse of fertilizers and pesticides, soil sterilization, and plant production in sterile soilless media. These technical advances have led to rapid production of pathogen-free plants, but VAM fungi have been sacrificed in the process. The potential impact of mycorrhizal deficiency on the “quality” of citrus and other woody crops for transplant has not been fully evaluated. With the realization that VAM fungi are essential for the growth of citrus in field soils, the question of how to reintroduce and gain maximum benefit from mycorrhizae in greenhouse production of citrus and other woody plants needs to be assessed.

Uptake and distribution of macro‐nutrients in trees of Coffea arabica L. in Kenya as affected by seasonal climatic differences and the presence of fruits

SUMMARYYoung to mature, conventionally managed, single‐stem, deblossomed and fruiting Arabica coffee trees growing in a fertile lateritic clay loam at Ruiru, were uprooted at 2‐ to 3‐monthly intervals between February 1967 and June 1968. Each was divided into ten parts which were dried, weighed, completely ground, and analysed for organic‐N, and total P, K, Ca and Mg.Mature trees took up about 100 g N, 6 g P, 100 g K, 35 g Ca and 10 g Mg each per annum, of which 8‐29 % (depending on the element) would be removed in an average crop of fruits, and 50‐81 % returned to the soil in prunings and fallen leaves. About half the P and K in senescing leaves was returned to the tree.N, K, Ca and Mg uptake by deblossomed trees was relatively rapid when they produced a large post‐drought ‘flush’ of shoot growth in February‐April 1967. Thereafter uptake kept pace with changes in dry weight, and the concentration of N, K, Ca and Mg in the tree parts changed relatively little. By contrast, P‐uptake was relatively rapid over the cool, dry season 1967 (June‐September), when the roots < 1 mm diameter grew rapidly, and during the subsequent Short Rains, but was slow during the hot, dry season 1968 (December‐March) when the surface 2‐3 ft of soil dried out. The concentration of P in the trees changed accordingly, especially in the branches. The flower buds took 39 % of the small total P‐uptake during the hot, dry season 1968.Trees bearing a light or moderate crop of fruits absorbed all the minerals determined more rapidly than deblossomed trees. The fruits on heavily fruiting trees took 89,95,98 and 99 % of the net current increment in Mg, K, organic‐N and P, respectively, but only 39 % of the Ca. All leaves on the fruiting trees became rich in Ca, and most of their woody parts were depleted of P.Mineral uptake in a coffee plantation is compared with that in plantations of other woody perennial crops, and some practical implications are noted in relation to soil and plant factors affecting the mineral nutrition of coffee in Kenya, with special reference to phosphates.