CAPÍTULO 4. MODELO DE COSTOS ABC PARA LA ENTIDAD PUNTO DE
4.2 FORMATOS PARA DISTRIBUCIÓN DE LOS COSTOS EN LA ENTIDAD
4.2.7 Asignación de Tiempo y Costo al Personal que Interviene en cada
In 1 987, a preliminary experiment was conducted in a glasshouse to select non injurious herbicides and appropriate application rates, which were then further evaluated in the field.
4.2.1 MATERIALS AND METHODS
4.2.1.1 Treatments Treatments included : Control Alachlor Chlorpropham Oryzalin Simazine : untreated.
: containing 500 g litre- 1 emulsifiable concentrate of 2-chloro-N (methoxymethyl) acetamide applied at 1 . 1 25 kg a.i. ha- 1 .
: containing 400 g litre- l emulsifiable concentrate of isopropyl 3- chlorophenyl carbamate applied at 1 kg a.i. ha- 1 ,
: containing 750 g kg- 1 wettable powder of 4-(dipropylamino)-3, 5- dinitrobenzenesulfonamide applied at 3 kg a.i. ha - 1 .
: containing 500 g litre- 1 suspension of 6-chloro-N ,N-diethyl-l ,3,5- triazine-2,4-diamine applied at 0.25 kg a.i, ha- 1 .
4.2.1.2 Establishment
Glassbouse trial
Aster seeds (Callistephus chinensis L.Nees.) cv. Kurenai were glasshouse sown in a 30x40x6 cm tray filled with Smith's potting mix containing peat, pumice and sand (Smith Soil Industries Limited, Auckland. New Zealand) on 20 October 1 987. The glasshouse temperature was 25±5 °e. After 14 days, seedlings were transplanted into 8 cm pots containing the same medium at one seedling per pot. This procedure was repeated again using cv. Powderpuff on 9 November 1987 so that two seedling age groups (44 and 24 days) were available for spraying on 3 December 1987. Pots were spaced 25x25 cm apart. Herbicides were sprayed over the top of the pot on an area basis via a portable 5 litre pressure sprayer. Treatments were allocated at random and replicated 6 times. There was one pot as one replicate of each treatment. Daily sprinkler irrigation began 24 h after herbicide application.
Field trial
The experimental site, soil preparation, germination procedure, handling of aster seedlings, transplanting and general management practices were identical to those described for the plant density experiment (Chapter 3). Seedlings of cv. Kurenai were transplanted into the field on 27 November 1 987 and of cv. Powderpuff on 17 December 1987. All plants were of the same seedling age (38 days old), but the number of days after transplanting differed when sprayed on 22 December 1 987 (Le. 25 and 5 days after transplanting for cv. Kurenai and cv. Powderpuff respectively). The same herbicides at the same rates as used in the glasshouse trial were applied in 0.5 I water per plot with the same sprayer, but the herbicides were sprayed between the plant rows to minimize direct plant contact.
A completely randomized design with three replicates of each treatment (including an untreated control) was used for each cultivar. Plot size was l x2.5 m2, and plant spacing was 25x25 cm, so that there were 40 plants per plot. Field layout is shown in Appendix 3.5
4.2.1.3 Data collection
Visual injury effe cts were observed and described at 1 , 2, 4 and 6 weeks after spraying in the glasshouse trial, and after 2 and 4 weeks in the field trial.
The number of weeds in the field trial at 30 days after spraying was determined by counting those present within a 0. 1 m2 quadrat placed at random in two positions within each plot. The mean of these two counts became the estimate of weed number. Weeds counted were converted to number m-2 before being square root transformed to overcome marked variance heterogeneity (Snedecor and Cochran,
1980).
4.2.2 RESULTS
Glasshouse trial
By 1 week after spraying, 24 day old Powderpuff seedlings sprayed with simazine were dying (Figure 4. 1 ) and both 24 (Powderpuff) and 44 (Kurenai) day old seedlings were dead after 2 weeks (Figures 4.2 and 4.3).
Alachlor caused leaf necrosis in seedlings of both cultivars especially at the leaf tip and the margin of young leaves. It had produced distorted growth by one week after application, which had become very obvious at 4 weeks after spraying (Figure 4.4). However, there were no effects on new shoot growth, or the flower head (Figure 4.5).
No phytotoxicity was recorded at any time following chlorpropham or oryzalin applications.
Field evaluation trial
No herbicide provided complete control of the weed species present, but oryzalin and simazine significantly reduced weed numbers (Figures 4.6 and 4.7) when applied 5 days after transplanting aster seedlings. However alachlor and simazine produced leaf necrosis, and although the symptoms were not as severe as those recorded in the glasshouse and aster plants recovered from this inj ury, their subsequent growth was checked.
51MAZlllE SURF LAN
<I ILORPROPHAM LASSO
Figure 4.1 Effe cts of herbicides on aster seedl i n g s a) 24 d ay old
cv. Powderpuff and b) 44 day old cv Kurenai at one week after
Figure 4.2
Figure 4.3
Effects of herbicides on 44 day old seedlings of aster cv. Kurenai at two weeks after spraying.
Simazine damage on aster seedlings a) 24 day old cv. Powderpuff and b) 44 day old cv. Kurenai at two weeks after spraying.
Figure 4.4 Effects of alachlor on aster seedlings a) 24 day old cv. Powderpuff and b) 44 day old cv. Kurenai at four weeks after spraying.
. Figure 4.5 No alaehlor damage found on a) new shoot growth of aster seedling ey Powderpuff at six weeks after spraying and b) aster flower head of both ey. Powderpuff and ey. Kurenai.
Figure 4.6 Field evaluation trial o f herbic ide application o n 5 day transplanted as ter seedlings (cv. Powderpuff) at a) 2 and b) 4 weeks after spraying.
Only simazine caused some damage (discoloration) when applied to seedlings 25
days after transplanting, but this effect disappeared within a short time. None of the herbicides were able to totall y con trol all weeds (Figure 4. 8), suggesting that for effective weed control, application m ust either be very soon after transplanting, or pre-transplanting. ---- N , 8 1 I-< (I.) ..c I-<
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0 Alachlol Slmtll'lno OrylsllnTreatment
Effects of herbicide applicalion (sprayed 5 days a fter a s ter transplanting) on weed number in aster cv. Powderpuff at four weeks after spraying.
Figure 4.8 Field evaluation trial of herbicide applic ation on 25 day
tran splanted a s ter seedlings (cv. Kure nai) at 4 weeks after