TheImprovement ofTropical and Subtropical Rangelands
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TheImprovement ofTropical and Subtropical Rangelands

TheImprovement ofTropical and Subtropical Rangelands TheImprovement ofTropical and Subtropical Rangelands

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17( IMPROVEMENT 0' mOPIGAL AND SUBTROPIGAL RANGELANDS FIGURE 7-11 TIlbepak colltaiDer for Ill.. propaptioll of pluta for hall__ plalltiDe ill harsh .it.. Ribbed walk of colltaiDer direct the powth of roota downward ud produce a root plq 0.2 III loq (McKell, 1986). Growth Container and Potting Media Barker and McKell (1979) grew fourwing saltbush and ~ wood (Sarco6catu vermictllatu) in four sis. and typ. of containers ranging from 98 to 1,147 ems and found that shoot length, shoot bioDUUl8, and root biomaa all increued with trise of container. A large variety of containers is available ranging from anall units in plastic or styrofoam trays to nUl'llery pots: an ideal container is Tubepak (figure 7-U). The b.t container trise for good field performance is not neeeaarily the beet container for eeedHng growth in the greenhouse. Planta grown in large containers generally perform beet in the field but require too much greenhouse space and are co8tly to handle and ship. The best container also vari. with plant speci. and environmental and soil conditions on the outplanting site. The potting mix should be near pH 5.5 and have an electrical conductivity reading of lea than 2.0 miJ)jmboe. Although there is much variation in potting mixes, mixtures of plain sand with sieved cow manure at a ratio of 1:1 are generally lI&tisfactory (Weber, 1986). However, in some instances, special mix. may be desirable. For example, Ferguson and MODSen (1974) found that mixes containing peat m08l'J and vermiculite produced better mountain-mahogany (Cercocar,u letliloti..) seedlings than did thOle containing sand. Ferguson (1980) studied 39 different potting media and found that no one mix was consistently superior. He did report that a potting mix of 50 percent peat moa, 30 percent arcillite aggregate, and 20 percent vermiculite is recommended for Bonneville saltbush (Atri,lez [ 1.)ltIZ ,d byCoogIe

REHABILITATION TECHNIQUES 175 6onnewlenftB) and might be appropriate for other plant species native to alkaline soils. Mixing native soil into standard potting mixes can increase growth of some chenopod species. A survey of nurseries growing desert shrubs reported a wide variety of potting mixes that contained such diveree components &8 sand, cinder, peat m088, comp08ted bark, charcoal, sawdust, vermiculite, perlite, and native soil. In lighter mixtures, it might be desirable to include some clay in the mixture, 80 that the root ball holds together during transplanting (Weber, 1986). Old termite mounds are often good sources of clay. The Hardening Phase The hardening phase is one of the most overlooked, yet most critical, periods in the growing cycle. It is relatively easy to produce an acceptable plant in the greenhouse, but these plants have a low rate of establishment unless they are properly conditioned so that they can survive and grow on the planting site. The two most important factors to consider in designing a hardening program are the planting date and the climate of the outplanting site. Many plant species grow very rapidly under the optimal conditions in the greenhouse, but this rapid growth consists of relatively large cells with thin cell walls and little tolerance to cold temperatures or moisture stress. Hardening is the proceM in which growth is reduced, stored carbohydrates accumulate, and the plant becomes better able to withstand adverse conditions (Penrose and Hansen, 1981). The hardening phase has three major objectives: 1. To minimize physical damage during handling, shipping, and planting; 2. To condition the plant to tolerate cold temperatures during refrigerated storage or after outplanting; and 3. To acclimatize plants to the outside environment and satisfy internal dormancy requirements of some species. Dormancy is another term that is often used in conjunction with hardiness. Dormant seedlings have been shown to have the ability to produce abundant new roots when planted in a favorable environment. This high root growth capacity should increase the ability of seedlings to survive and grow on harsh sites. Both dormancy and cold hardiness can be induced by proper scheduling of the hardening regime. Hardiness should be induced in stages, and the process usually takes at least 6-8 weeks. The hardening begins in the greenhouse by

17( IMPROVEMENT 0' mOPIGAL AND SUBTROPIGAL RANGELANDS<br />

FIGURE 7-11 TIlbepak colltaiDer for Ill.. propaptioll of pluta for hall__<br />

plalltiDe ill harsh .it.. Ribbed walk of colltaiDer direct the powth of roota<br />

downward ud produce a root plq 0.2 III loq (McKell, 1986).<br />

Growth Container <strong>and</strong> Potting Media<br />

Barker <strong>and</strong> McKell (1979) grew fourwing saltbush <strong>and</strong> ~<br />

wood (Sarco6catu vermictllatu) in four sis. <strong>and</strong> typ. of containers<br />

ranging from 98 to 1,147 ems <strong>and</strong> found that shoot length, shoot<br />

bioDUUl8, <strong>and</strong> root biomaa all increued with trise of container. A<br />

large variety of containers is available ranging from anall units in<br />

plastic or styrofoam trays to nUl'llery pots: an ideal container is<br />

Tubepak (figure 7-U).<br />

The b.t container trise for good field performance is not neeeaarily<br />

the beet container for eeedHng growth in the greenhouse.<br />

Planta grown in large containers generally perform beet in the field<br />

but require too much greenhouse space <strong>and</strong> are co8tly to h<strong>and</strong>le <strong>and</strong><br />

ship. The best container also vari. with plant speci. <strong>and</strong> environmental<br />

<strong>and</strong> soil conditions on the outplanting site.<br />

The potting mix should be near pH 5.5 <strong>and</strong> have an electrical<br />

conductivity reading of lea than 2.0 miJ)jmboe. Although there is<br />

much variation in potting mixes, mixtures of plain s<strong>and</strong> with sieved<br />

cow manure at a ratio of 1:1 are generally lI&tisfactory (Weber, 1986).<br />

However, in some instances, special mix. may be desirable. For<br />

example, Ferguson <strong>and</strong> MODSen (1974) found that mixes containing<br />

peat m08l'J <strong>and</strong> vermiculite produced better mountain-mahogany<br />

(Cercocar,u letliloti..) seedlings than did thOle containing s<strong>and</strong>.<br />

Ferguson (1980) studied 39 different potting media <strong>and</strong> found that<br />

no one mix was consistently superior. He did report that a potting<br />

mix of 50 percent peat moa, 30 percent arcillite aggregate, <strong>and</strong> 20<br />

percent vermiculite is recommended for Bonneville saltbush (Atri,lez<br />

[ 1.)ltIZ ,d byCoogIe

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