**3. Establishment of** *Arachis pintoi* **in native pastures of Mexico**

Research results from the hot humid areas of México and from other parts of Latin America showed that the forage legume *Arachis pintoi* CIAT 17434 has the ability to be associated with grasses, because it has shows better persistence than other legumes and also has high nutritive value and palatability [16, 17-20]. *A. pintoi* establishment techniques range from a complete soil tillage and planting with seed to zero tillage and planting with vegetative ma‐ terial (stolons) into an existing pasture [17]. The objective of this study was to evaluate the agronomic performance of different techniques of establishing *A. pintoi* CIAT 17434, as well as the accessions CIAT 18744 and 18748, into existing native pastures in the humid tropics of the coastal plains of the Gulf of México.

#### **3.1. Materials and methods**

#### *3.1.1. Site characteristics*

Three experiments were conducted during 1991 and 1996 at the Centre for Teaching, Re‐ search and Extension in Tropical Animal Husbandry (CEIEGT, its acronym in Spanish) of the Faculty of Veterinary Medicine, of the National University of Mexico (UNAM). The Cen‐ tre (CEIEGT) is located in the eastern coastal plain of México about 40 km West of the Gulf of México coast line at 20° 02' N and 97° 06' W, at 112 m a. s. l.

The climate is hot and humid, with rains all year round. Mean yearly rainfall was 1,917±356 mm from 1980 to 1997. Monthly rainfall is highly variable being September (322 mm) and October (248 mm) the rainiest months while March (85 mm) is the driest. The coldest and hottest months are January (18.9 °C) and June (27.8 °C). Minimum daily temperatures from November to February (winter) are around the critical range of 8-10 °C, below which the growth of C4 tropical grasses is severely reduced [21-23]. These combinations of rainfall and temperature lead to a seasonal DM production pattern, a common situation in the tropics of Latin America: A high growth rate on the rainy season followed by poor growth during the winter and dry seasons.

The experiments were conducted in different years. Temperatures were typical of each sea‐ son, but the current maxima were below, and the current minima above the long term (1980-1997) mean (Figure 3a). Total rainfall during experiment 1, December 1991 to Septem‐ ber 1992, was 39% above average (Figure 3b). Rainfall in the experimental planting seasons was 339 mm in winter (November 29, 1991 to February 14, 1992), 637 mm in the dry season (March 2 to May 18 of 1992) and 1,352 mm in the rainy season (July 2 to September 17 of 1992). Rainfall was 19% above average during experiment 2 in 1993, but rains in 1996 were 43% below average for experiment 3 (Figure 3b).

**Figure 3.** Current and long term monthly temperatures (a) and rainfall (b) for the 3 experiments.

this accesion to cover the ground. Regarding the second experiment, the disking treatment, proved to be the best treatment for the establishment of the legume, but the costs of estab‐ lishment will vary depending on the inputs applied, but a long-term coverage will absorb

Research results from the hot humid areas of México and from other parts of Latin America showed that the forage legume *Arachis pintoi* CIAT 17434 has the ability to be associated with grasses, because it has shows better persistence than other legumes and also has high nutritive value and palatability [16, 17-20]. *A. pintoi* establishment techniques range from a complete soil tillage and planting with seed to zero tillage and planting with vegetative ma‐ terial (stolons) into an existing pasture [17]. The objective of this study was to evaluate the agronomic performance of different techniques of establishing *A. pintoi* CIAT 17434, as well as the accessions CIAT 18744 and 18748, into existing native pastures in the humid tropics of

Three experiments were conducted during 1991 and 1996 at the Centre for Teaching, Re‐ search and Extension in Tropical Animal Husbandry (CEIEGT, its acronym in Spanish) of the Faculty of Veterinary Medicine, of the National University of Mexico (UNAM). The Cen‐ tre (CEIEGT) is located in the eastern coastal plain of México about 40 km West of the Gulf

The climate is hot and humid, with rains all year round. Mean yearly rainfall was 1,917±356 mm from 1980 to 1997. Monthly rainfall is highly variable being September (322 mm) and October (248 mm) the rainiest months while March (85 mm) is the driest. The coldest and hottest months are January (18.9 °C) and June (27.8 °C). Minimum daily temperatures from November to February (winter) are around the critical range of 8-10 °C, below which the growth of C4 tropical grasses is severely reduced [21-23]. These combinations of rainfall and temperature lead to a seasonal DM production pattern, a common situation in the tropics of Latin America: A high growth rate on the rainy season followed by poor growth during the

The experiments were conducted in different years. Temperatures were typical of each sea‐ son, but the current maxima were below, and the current minima above the long term (1980-1997) mean (Figure 3a). Total rainfall during experiment 1, December 1991 to Septem‐ ber 1992, was 39% above average (Figure 3b). Rainfall in the experimental planting seasons was 339 mm in winter (November 29, 1991 to February 14, 1992), 637 mm in the dry season (March 2 to May 18 of 1992) and 1,352 mm in the rainy season (July 2 to September 17 of

**3. Establishment of** *Arachis pintoi* **in native pastures of Mexico**

these costs converting this costs in an effective alternative.

of México coast line at 20° 02' N and 97° 06' W, at 112 m a. s. l.

the coastal plains of the Gulf of México.

**3.1. Materials and methods**

*3.1.1. Site characteristics*

54 Soil Fertility

winter and dry seasons.

The soils are acid Ultisols (Durustults), with a range in pH from 4.1 to 5.2, and an impermea‐ ble hardpan between 0 and 25 cm in depth, that result in a inadequate drainage during the rainy and winter seasons. The soil texture is clay-loam with low levels of P (< 3 ppm), S (< 30 ppm), Ca (< 3 meq/100 g) y K (< 0.2 meq/100 g). Both cation exchange capacity and alumi‐ num saturation increase with depth, but the latter do not reach toxic levels for pasture plants [24].

#### *3.1.2. Experiment 1. Reduced and zero tillage, with or without fertilisation*

The study was conducted to test the combined effects of tillage type: reduced and zero, and fertilisation with (kg/ha): P 22; S 25; K 18, Mg 20; Ca 100; Zn 3; Cu 2 and B 1, or no fertilisa‐ tion, in a four treatment combination: T1, reduced tillage and fertilisation; T2, reduced till‐ age without fertilisation; T3, zero tillage and fertilisation; and T4, zero tillage without fertilisation. Reduced tillage consisted of four passes of a disk harrow, while zero tillage on‐ ly required the elimination of pasture vegetation by machete to ground level.

The experimental area was 2,000 m2 (50 m x 40 m split in two plots of 1,000 m2 - 25 m x 40 m). These plots were divided in two sub plots of 500 m2 (25 m x 20 m), of which one sub plot was fertilised. Three 2,000 m2 -experimental areas were used: one per each climatic season (winter, dry and rainy season).

*Arachis pintoi* was planted on sub-plots of 500 m2 on 29 November, 1991 (winter season), 2 March, 1992 (dry season) and 2 July, 1992 (rainy season). Three to four stolons, approximate‐ ly 15 cm in length and with five nodes per stolon, were planted per planting position. On the reduced tillage treatments the distance between rows and planting positions were 1.0 m and 0.5 m, respectively. Planting was done on 3 m wide strips, which alternated with 3 m intact native pasture strips. Three rows of the legume were planted per strip and 3 strips were contained in a subplot, being the sampling quadrat size 3.0 m x 1.5 m. On the zero till‐ age treatment, distance between rows and positions was 2 m and 0.5 m, respectively, with the subplot containing nine sampling rows also and a sampling quadrat dimensions of 6 m x 3 m. Even though this planting arrangement was confounded with tillage treatments, it gave a similar number of planting positions per sub-plot and two sampling hills/m2 in each sam‐ pling quadrat, regardless of type of tillage. Fertiliser was broadcast 30 days after planting.

m and 0.5 m, respectively. Seed pods were placed in a 5 cm deep hole made with pointed wooden stick, and lightly covered with soil by the planter's foot. Three replicates were

Soil Management for the Establishment of the Forage Legume Arachis pintoi as a Mean to Improve Soil Fertility...

(PH, cm), on each plant within the sampling quadrat, measured with a ruler from the soil surface to the uppermost part of the plant; and 3) soil covered by the legume or cover (COV,

into 25 squares, which was placed over the row. These measurements were done on weeks 4, 8 and 12 after planting [26]. In experiment 1, PH was not measured, but COV was meas‐

In experiment 1, there were no field replications, since it was perceived that treatments ap‐ plied in larger areas would have a closer resemblance to that of farmers' fields. Also, if sev‐ eral sampling quadrats were used within each treatment plot, this would yield information as useful as that obtained from randomised complete block designs. In experiments 2 and 3, the design was a randomised complete block design with 3 blocks as replicates. The treat‐ ment arrangement was a split-plot in experiment 2, where the main plot was the combina‐ tion of type of pasture vegetation control (slashing and herbicide), while the combinations of burning (with and without) and P application (with and without) were the sub-plots; addi‐ tionally the effect of time after planting was considered a sub-sub-plot. The treatment ar‐ rangement of the third experiment was a split plot, in which the main factor was the combination of month of planting by accession and time after planting the sub-plot. Here,

. Analyses of variance were done with linear additive models in accordance to

the experimental design [27]. The natural log transformation of the response variable was used if its response to time was exponential. If necessary, linear or exponential relationships provided rates of increase with time in the measured variables. Also, means comparisons

The main effect of treatment on plant number (PN) was highly significant (P<0.01) in all sea‐ sons. The linear effect of week after planting was highly significant (P<0.01) on PN in the winter season of 1991-92 and the rainy season of 1992, but it was not significant (P>0.05) in the dry season of 1992 (Table 6). There was no significant treatment x week interaction on PN in any season. The main effects of treatment and week after planting and its interaction were highly significant (P<0.01) on COV, except for the interaction in the rainy season. Weeks to reach 50% cover were 21, for T2 (winter season) and T4 (dry season); and 20, for T1

) by counting; 2) plant height

http://dx.doi.org/10.5772/53318

57

", in order to be clearer and avoid fractions

quadrat, divided

planted on August 2 and three on September 3, 1996. Fertiliser was not applied.

% of quadrat area covered by the legume) measured with the aid of a 1 m2

**3.2. Measurements and statistical analyses**

ured again at 24 weeks after planting.

number of plants was expressed as "plants/50 m2

using Tukey's test were done when was necessary.

and T4 in the rainy season (Table 7).

*3.3.1. Experiment 1. Reduced and zero tillage, with or without fertilisation*

of plant/m2

**3.3. Results**

The response variables were: 1) plant number (PN, plants/m2

## *3.1.3. Experiment 2. Type of control of native pasture growth, with or without P fertiliser*

This experiment tested the combined effect of the type of pasture vegetation control: herbi‐ cide (glyphosate) or slashing (by machete) with or without burning of dead vegetation, and with or without localised P-fertilisation which resulted in eight treatment combinations. The choice of treatments attempted to reduce competition to *A*. *pintoi* from existing native pas‐ ture vegetation, enhance legume establishment and early growth, following the approach described by [25] for the establishment of legumes into existing Speargrass (*Heteropogon con‐ tortus*) native pastures, in Australia.

Slashing was done by machete and burning was carried out between 1-5 days after slashing. A 2% aqueous solution of glyphosate (480 g of isopropyl amine salt of glyphosate/l) was ap‐ plied on a 0.25 m wide strip 15 days before planting; burning was done 15 days after herbi‐ cide application.

The planting legume was done between June 28 and July 3. Application of herbicide and herbicide plus burning, and slashing or slashing plus burning, were applied 15-16 days and 3-5 days earlier, respectively. Vegetative material, 0.25 m length stolons with eight nodes, was used for planting. This material was inoculated just prior to planting with a specific *Bradyrhizobium* culture obtained by suspension of 1 kg of profusely nodulated *A. pintoi* ground roots in a solution 7.5 litres of water and 1.5 litres of sugarcane molasses. Three sto‐ lons per planting position were put in a hole and covered with soil, allowing about 1/3 of the stolon to remain above ground. Distances among rows and planting position were 1.0 m and 0.5 m, respectively. The sub plot (10.0 m x 6.5 m) had 10 rows with 14 planting posi‐ tions/row. Two sampling quadrats (2 m x 1 m) each with 4 planting positions were random‐ ly allocated per sub plot. Single super phosphate (30 kg of P/ha) was applied at planting in a 0.07 m depth hole adjacent to the planting position.
