*4.1.1. Characteristics of the experimental site*

The research was conducted at the Centre for Teaching, Research and Extension in Tropical Animal Husbandry of the Faculty of Veterinary Medicine, of the National University of Mexico (UNAM), located in north-central region State of Veracruz, 20 ° 4 'north longitude 97 ° 3' W and a height of 105 meters above sea level. The climate is hot and humid with rain all year, type Af (m) with average daily temperature of 23.4 ° C and average annual total pre‐ cipitation of 1840 mm (1980-1989). The soil texture ranges from sandy loam to sandy clay. The area has a hard horizon with low permeability that occurs between 5 and 25 cm deep. The soils are acidic (pH 4.1 to 5.2), and are classified as Ultisols.

We used an area of 6.000 m2 of degraded native pasture grazed by cattle. The treatments were the type of weeding (slashing, S; and herbicide, H) and the burning (B) application or not (with + B and without -B), to temporarily control the growth of existing vegetation (larg‐ er plots), and thus prove its effectiveness to allow the establishment of the legumes *Arachis pintoi* CIA 17434 (Ap) and *Pueraria phaseoloides* CIAT 9900 (Pp). Additionally we evaluated the application of phosphate fertilizer or not (+P addition; no-P as single superphosphate). The factorial combination between legumes and fertilizer was the subplot.

Treatments were applied between 28 May and 3 June 1993. The slashing (S) was a machete to the whole plot. In S + B, the burning was applied between one and five days after slash‐ ing. The application of herbicide (H) was done using a backpack sprayer, applied in bands 50 cm wide, spaced 1 m apart from the center of each. The dose was 0.96 kg (2 l) of a nonse‐ lective systemic herbicide (Glyphosate). The product was dissolved in 200 l of water and ap‐ plied 15 days before seeding. In H + B, herbicide application was the same way as above, burning 15 days after application, only the bands where the herbicide is applied.

*Ap* vegetative material, was inoculated with the specific *Rhizobium*, by means of a suspen‐ sion prepared with nodulated roots, washed and crushed to release *Rhizobium* bacteria, then adding cold water and molasses, placing the suspension in a refrigerator, performing all procedure in the shade. Each kg of root was added 1.5 kg of molasses (as adherent) and 7.5 l of cold water.

Legumes were planted between 3 and 5 days after applying treatments S or S + B, and be‐ tween 15 and 16 days after applying treatments H or H + B. *Ap* was planted with stolons of 20 cm long, inoculated with the suspension of *Rhizobium* already described. By planting, we used a metal digging stick, to make a biased hole of 15 cm lenght and 5 cm depth. Three stolons were placed by hole and soil was compacted with foot to ensure contact with the ground. The distance between plants and rows was 0.5 and 1 m, respectively.

Plant height. - Analysis of variance showed highly significant differences (P <0.01) between the species: *Ap* with 18.3 cm and 9.5 cm with *Pp* (Figure 6). This difference is attributed to *Ap* was seeded with plant material starting its growth as seedling, which gave to Ap an advant‐

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65

**Figure 6.** Effect of type of control weeds (herbicide –H- and slashing –S-), with and without P fertilizer over plant

The interaction slashing X burning was highly significant (P <0.01). The application of H+B resulted in greater plant height with 16.0 cm, followed by S-B with 15.6 cm, being H-B meth‐ od the lowest height with 11.1 cm. In the case of H+B, the plant height was attributed to no competition between the legume and native grasses; also, burning causes release of soil nu‐

Burning, releases mineral nutrients immobilized in plant tissues, and others are trans‐ formed into simple soluble salts, readily available to the plant [43]. In the treatment of S-B, the largest plant height was mainly due to competition for sunlight by the grass. Competition for sunlight between *Aeschynomene*, seeded with the grass *Hemarthria altissi‐*

trients that legumes can absorb quickly, making their establishment more effectively.

age over *Pp* that was sown with seed.

height of *Arachis pintoi* and *Pueraria phaseoloides*.

For planting of kudzu (*Pp*) botanical seed was used, previously scarified with sulfuric acid to 98% for 10 minutes. This ensured the seed germination in three days post seeding. The effectiveness of this treatment has been verified by other researchers [40].

Planting density was 2 kg/ha of pure and viable seed. After scarified, the seed was inoculat‐ ed and seeded similarly as *Ap* placing about 8 seeds per site, but was not covered prevent‐ ing soil compaction. The distance between plants and rows was 0.5 and 1 m, respectively. Single superphosphate (333 kg/ha = 30 kg P/ha) was applied at planting time in 5 cm band from the seed or plant material.

We used two sampling sites per plot at random. Firstly, two rows of each plot were chosen, and then the sampling site within each row. The recommended [26] variables were, number of plants, plant height (cm) and coverage (%) at 4, 8 and 12 weeks post seeding. A random‐ ized complete block design was used, with three replications and a split-plot arrangement, with the factorial combination between weeding and burning as main plots, and the combi‐ nation of the two legumes with or without fertilization as subplots. We considered the costs for materials and labor costs per treatment.

#### **4.2. Results and discussion**

Climate. – The climatic parameters of precipitation and temperature were recorded from May to September 1993. The monthly average temperature was similar for the periods, rang‐ ing from 25.5 to 27.0 °C. The lowest rainfall occurred in July and highest in September with 109 and 360 mm respectively. Rainfall totaled 1257 mm. This caused flooding which affected the establishment of each legume.

Number of plants. - Analysis of variance indicated that there was a highly significant effect (P <0.01) of the species, with 1.77 and 0.55 for *Ap* plants/m2 plants / m2 for *Pp*. The number of plants for *Ap* can be considered acceptable, even expected 2 plants/m2 . Flooding caused by high rainfall brought rot of stolons.

The small number of *Pp* plants is also attributed to the seed rot because of soil waterlogging. It has been mentioned [41] that heavy rainfall limits the development of Kudzu (*Pp*). Also, surprisingly, the number of plants decreased as time passes (P <0.01): There were 1.27, 1.18 and 1.0 plants/m2 for first, second and third samples. Effects such as slashing, burning, and their interaction were not significant (P> 0.05), which coincides with other experiment [42]. These authors, who established three species of legumes (*Centrosema pubescens*, *Macroptilium atropurpureum* and *clitoria ternatea*) using total soil preparation, harrowing, plowing and burning, with no significant difference found (P> 0.05) among the different methods,and concluded that burning favored the establishment of legumes.

Plant height. - Analysis of variance showed highly significant differences (P <0.01) between the species: *Ap* with 18.3 cm and 9.5 cm with *Pp* (Figure 6). This difference is attributed to *Ap* was seeded with plant material starting its growth as seedling, which gave to Ap an advant‐ age over *Pp* that was sown with seed.

Legumes were planted between 3 and 5 days after applying treatments S or S + B, and be‐ tween 15 and 16 days after applying treatments H or H + B. *Ap* was planted with stolons of 20 cm long, inoculated with the suspension of *Rhizobium* already described. By planting, we used a metal digging stick, to make a biased hole of 15 cm lenght and 5 cm depth. Three stolons were placed by hole and soil was compacted with foot to ensure contact with the

For planting of kudzu (*Pp*) botanical seed was used, previously scarified with sulfuric acid to 98% for 10 minutes. This ensured the seed germination in three days post seeding. The

Planting density was 2 kg/ha of pure and viable seed. After scarified, the seed was inoculat‐ ed and seeded similarly as *Ap* placing about 8 seeds per site, but was not covered prevent‐ ing soil compaction. The distance between plants and rows was 0.5 and 1 m, respectively. Single superphosphate (333 kg/ha = 30 kg P/ha) was applied at planting time in 5 cm band

We used two sampling sites per plot at random. Firstly, two rows of each plot were chosen, and then the sampling site within each row. The recommended [26] variables were, number of plants, plant height (cm) and coverage (%) at 4, 8 and 12 weeks post seeding. A random‐ ized complete block design was used, with three replications and a split-plot arrangement, with the factorial combination between weeding and burning as main plots, and the combi‐ nation of the two legumes with or without fertilization as subplots. We considered the costs

Climate. – The climatic parameters of precipitation and temperature were recorded from May to September 1993. The monthly average temperature was similar for the periods, rang‐ ing from 25.5 to 27.0 °C. The lowest rainfall occurred in July and highest in September with 109 and 360 mm respectively. Rainfall totaled 1257 mm. This caused flooding which affected

Number of plants. - Analysis of variance indicated that there was a highly significant effect

The small number of *Pp* plants is also attributed to the seed rot because of soil waterlogging. It has been mentioned [41] that heavy rainfall limits the development of Kudzu (*Pp*). Also, surprisingly, the number of plants decreased as time passes (P <0.01): There were 1.27, 1.18

their interaction were not significant (P> 0.05), which coincides with other experiment [42]. These authors, who established three species of legumes (*Centrosema pubescens*, *Macroptilium atropurpureum* and *clitoria ternatea*) using total soil preparation, harrowing, plowing and burning, with no significant difference found (P> 0.05) among the different methods,and

for first, second and third samples. Effects such as slashing, burning, and

plants / m2

for *Pp*. The number of

. Flooding caused by

ground. The distance between plants and rows was 0.5 and 1 m, respectively.

effectiveness of this treatment has been verified by other researchers [40].

from the seed or plant material.

64 Soil Fertility

**4.2. Results and discussion**

the establishment of each legume.

high rainfall brought rot of stolons.

and 1.0 plants/m2

(P <0.01) of the species, with 1.77 and 0.55 for *Ap* plants/m2

concluded that burning favored the establishment of legumes.

plants for *Ap* can be considered acceptable, even expected 2 plants/m2

for materials and labor costs per treatment.

**Figure 6.** Effect of type of control weeds (herbicide –H- and slashing –S-), with and without P fertilizer over plant height of *Arachis pintoi* and *Pueraria phaseoloides*.

The interaction slashing X burning was highly significant (P <0.01). The application of H+B resulted in greater plant height with 16.0 cm, followed by S-B with 15.6 cm, being H-B meth‐ od the lowest height with 11.1 cm. In the case of H+B, the plant height was attributed to no competition between the legume and native grasses; also, burning causes release of soil nu‐ trients that legumes can absorb quickly, making their establishment more effectively.

Burning, releases mineral nutrients immobilized in plant tissues, and others are trans‐ formed into simple soluble salts, readily available to the plant [43]. In the treatment of S-B, the largest plant height was mainly due to competition for sunlight by the grass. Competition for sunlight between *Aeschynomene*, seeded with the grass *Hemarthria altissi‐* *ma* resulted in greater height during legume establishment [44]. Here, the combination of H-B produced lesser height.

that the best method was the application of systemic herbicide, achieving a plant height of 162.5 m and plant coverage of 96% to 5 months post seeding, concluding that the best pro‐

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67

Coverage. - The analysis of variance showed highly significant differences (P <0.01) between species: *Ap* showed a coverage of 2.6% and 0.5% Kudzu. We also found highly significant difference (P <0.01) between samples, with 0.7, 1.2 and 2.8% at 4, 8 and 12 weeks post seed‐ ing. The species x sampling interaction was highly significant (P <0.01). *Ap* was the best spe‐ cies, averaging 1.2, 2.0 and 4.6% while *Pp* averaged 0.2, 0.5 and 0.9% for the same samples

**Figure 8.** Soil coverage (%) according to the total experimental area, by *Arachis pintoi* (Ap) and Pueraria phaseoloides

The interaction slashing x fertilization x burning was also significant (P <0.05), resulting in the best combination of the H+B+P with 2.5% coverage, followed by S-B-P with 1.9%. Burn‐ ing + fertilization promoted a good establishment of legumes. The combinations in which was planted after herbicide application, showed no significant differences for the variable

The burning x slashing x sampling interaction was also significant (P 0 <0.05). In the third sampling, treatment H+B+P was the best combination of coverage averaging 4.2%, followed by H-B-P with 2.4%. The other combinations were not significantly different from each oth‐ er. The combination S+B+P coverage reached 3.7%, which is the highest value, which shows that the burning had positive influence on legume development, although interacted differ‐

The elimination of competition below and above ground, by applying H+B+P promotes the successful establishment of legumes. The lack of competition, plus the application of P, al‐

moter of the successful establishment of this legume was the control of vegetation.

(Figure 8).

coverage.

(Pp) at 4, 8 and 12 weeks afetr planting date.

ently with the type of weeding and fertilizing.

Sampling at 4, 8 and 12 weeks showed highly significant differences (P <0.01) with 7.10, 12.23 and 22.39 cm, respectively (Figure 7). This increase in plant height in time was an ex‐ pected effect.

**Figure 7.** Effect of type of control weeds (herbicide –H- and slashing –S-), durin the three climatic evaluation seasons over the plant height of *Arachis pintoi* (Ap) and *Pueraria phaseoloides* (Pp).

The interactions species x weeding x fertilization, and weeding x species x sampling were significant (P <0.05), while weeding x fertilization x species x sampling were highly signifi‐ cant (P <0.01). Most probably is that the latter would have been highly significant because it contained the first two.

These results coincide with those of an experiment in Cuba [45], who evaluated different methods of control vegetation during the establishment of *Leucana leucocephala*, and reported that the best method was the application of systemic herbicide, achieving a plant height of 162.5 m and plant coverage of 96% to 5 months post seeding, concluding that the best pro‐ moter of the successful establishment of this legume was the control of vegetation.

*ma* resulted in greater height during legume establishment [44]. Here, the combination of

Sampling at 4, 8 and 12 weeks showed highly significant differences (P <0.01) with 7.10, 12.23 and 22.39 cm, respectively (Figure 7). This increase in plant height in time was an ex‐

**Figure 7.** Effect of type of control weeds (herbicide –H- and slashing –S-), durin the three climatic evaluation seasons

The interactions species x weeding x fertilization, and weeding x species x sampling were significant (P <0.05), while weeding x fertilization x species x sampling were highly signifi‐ cant (P <0.01). Most probably is that the latter would have been highly significant because it

These results coincide with those of an experiment in Cuba [45], who evaluated different methods of control vegetation during the establishment of *Leucana leucocephala*, and reported

over the plant height of *Arachis pintoi* (Ap) and *Pueraria phaseoloides* (Pp).

contained the first two.

H-B produced lesser height.

pected effect.

66 Soil Fertility

Coverage. - The analysis of variance showed highly significant differences (P <0.01) between species: *Ap* showed a coverage of 2.6% and 0.5% Kudzu. We also found highly significant difference (P <0.01) between samples, with 0.7, 1.2 and 2.8% at 4, 8 and 12 weeks post seed‐ ing. The species x sampling interaction was highly significant (P <0.01). *Ap* was the best spe‐ cies, averaging 1.2, 2.0 and 4.6% while *Pp* averaged 0.2, 0.5 and 0.9% for the same samples (Figure 8).

**Figure 8.** Soil coverage (%) according to the total experimental area, by *Arachis pintoi* (Ap) and Pueraria phaseoloides (Pp) at 4, 8 and 12 weeks afetr planting date.

The interaction slashing x fertilization x burning was also significant (P <0.05), resulting in the best combination of the H+B+P with 2.5% coverage, followed by S-B-P with 1.9%. Burn‐ ing + fertilization promoted a good establishment of legumes. The combinations in which was planted after herbicide application, showed no significant differences for the variable coverage.

The burning x slashing x sampling interaction was also significant (P 0 <0.05). In the third sampling, treatment H+B+P was the best combination of coverage averaging 4.2%, followed by H-B-P with 2.4%. The other combinations were not significantly different from each oth‐ er. The combination S+B+P coverage reached 3.7%, which is the highest value, which shows that the burning had positive influence on legume development, although interacted differ‐ ently with the type of weeding and fertilizing.

The elimination of competition below and above ground, by applying H+B+P promotes the successful establishment of legumes. The lack of competition, plus the application of P, al‐ lowed to establish successfully the legume Siratro (*Macroptilium atropurpureum*) on the na‐ tive grass [25].

Also, financial constraints of most producers in the tropics must be considered when trying to introduce forage species [40]; so it is justified, evaluate and implement systems-on plant‐ ing native vegetation, different from the traditional, in order to encourage the adoption of

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In order to improve the botanical composition of native pasture in north-central region of Veracruz, Mexico, was evaluated two methods of establishment to incorporate the forage le‐

Centre for Teaching, Research and Extension in Tropical Animal Husbandry of the Faculty of Veterinary Medicine, of the National University of Mexico (UNAM), located in the mu‐ nicipality of Tlapacoyan, Veracruz, Mexico, 20 ° 03 'north latitude and 97 ° 03' west longi‐ tude, 151 m. The climate is hot and humid on the type Af (m) (e), with an average temperature of 23.4 ° C and an average annual rainfall of 1980 mm. Soil characteristics are

Sand 22.2 8.6 - 18.2 Clay 47.0 70.9 - 57.5 Silt 30.8 20.5 - 24.4

pH 5.0 5.1 5.3 5.3 O.M. (%) 3.5 1.7 1.0 1.2 P (ppm) 5.0 6.4 4.4 2.0 S (ppm) 32.0 54.4 41.6 34.1 Ca (meq/100 g) 5.1 5.0 4.2 4.0 Mg 1.8 1.5 1.4 1.4 K 0.8 0.3 0.3 0.3 Al 0.2 0.1 0.1 0.1 CEC (meq/100 g) 7.1 6.8 5.7 5.5 Al saturation (%) 2.8 1.5 1.7 1.8

**Table 12.** Chemical and physical characterisics of the experimental soil. Veracruz, Mexico.

**Soil depth (cm) 0-10 10-20 20-30 30-40**

new and improved grass species, the lower potential economic costs.

gume *Arachis pintoi* CIAT 17434.

**5.1. Materials and methods**

presented in the Table 12.

**Properties**

**Texture** (%)

**Chemicals**

*5.1.1. Location*

The higher cost of treatment to establish *Ap*, was the S+B+P, or S+B-P (USD \$ 195.00/ha), whereas the application of H-B-P was less expensive to establish *Pp* (USD \$ 86.00/ha). Herbi‐ cide application was more economical compared to the slashing treatment. (Table 11).

#### **4.3. Conclusions**

The banded herbicide application without application of fertilizer is the best method for introducing vegetatively Ap in native grass pastures in north-central region of Veracruz State, Mexico.


**Table 11.** Economic costs of treatments on the establishment of *Arachis pintoi* and Pueraria phaseoloides. Mexico, August 1996.
