*2.5.1. First experiment*

The number of plants for the three ecotypes at 12 weeks, was on average lower compared with those found by [10] in one of three experiments with *Arachis pintoi* in native pastures of that region. He observed that Ap 17434 presented at that time more than 10 plants/m2 , using plant material grown in field where vegetation was controlled with a machete and herbi‐ cide, with or without burning the dead material and fertilized or not with P. The smaller number of plants found here could be due in part to the month after planting (May) was relatively dry (<50 mm), consequently affecting plant emergence. In the mentioned experi‐ ment [10] the growth period immediately to planting date had higher humidity (> 150 mm).


PD1 and PD2= Plants sown at 35 and 50 cm within the furrow respectively.

+F: With fertilization (kg/ha: 50 P2O5, 50 K2O, 20 Mg2SO4); and, -F: without fertilization.

\*D=Disking, Ch=Chiseling, and H=Hoeing.

\*\*P: Probability level.

**Table 3.** Number of plants of *Arachis pintoi* and its height (Averages; standard error in parentheses), reached five months after planting date according to soil preparation, plant density (PD) and fertilizer application or not (F).

Moreover, it appears that the ecotypes evaluated here shown in the early stages of establish‐ ment a tendency of erect growth. It has been indicated [10] a range from 14.4 to 21.0 cm at 12 weeks post planting date, regardless of the treatments.

With respect to coverage, the R2 values showed good predictive power for the environmen‐ tal conditions during the study. No one model predicted a maximum coverage of 100%, be‐ cause the measurement time was only 24 weeks.

In Colombia [4] evaluated in citrus plantations the same ecotypes, and found 8 months af‐ ter that Ap 17434 was much lower coverage (32%) compared with the other ones (73% on average). On native pastures [10], found in another experiment with Ap 17434 that its es‐ tablishment was even slower, since the accession planted with no-tillage or reduced till‐ age, with or without fertilization (P, K, Mg, Ca, Zn, Cu and B), needed 20 to 21 weeks to achieve 50% coverage.

The lower rate of coverage by the accession 17434 was also confirmed [11], on the experi‐ ment developed in this same region comparing four species of forage legumes (*Desmodium ovalifolium*, *Neonotonia wightii*, *Pueraria phaseoloides* and *Stizolobium deerigianum*) associated to a citrus plantation. This slowness in the establishment was also reported in Costa Rica [12] to associate in banana plantations.

Moreover, the ecotypes established by seed showed a higher rate of coverage, however, however, these differences in the velocity of establishing tend to disappear as time passes.

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

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53

The coverage obtained with the disking treatment with plants every 35 cm along the furrow, and with or without fertilization are considered acceptable and are superior to those report‐ ed for *Ap* 18748 in coffee plantations of Nicaragua for high plant densities using vegetative material (strips of 3.3 m wide, with furrows 50 cm) and three weedings in the first 90 days [13]. This author reported that at 158 days post seeding, the legume exceeded 60% of ground cover. In Brazil [14], assessed *A*. *pintoi* at plant densities of 8 to 16 plants/linear m, reaching a 50% coverage to 84 and 68 days post seeding, respectively; whether the separation between furrows was 25 or 50 cm. The above percentages indicate superior performance under these

Respect to changes detected in the soil properties, the increase in the concentration of N could be attributed to a transfer to the soil of the element present in the leaves of *Arachis pintoi* by the effect of decomposition thereof. In this regard, [15] estimated litter decomposi‐ tion of grasses and legumes, among whom was *A*. *pintoi*. They found that the decomposition of organic matter and nitrogen in leaves of this legume, along with that of *Stylosanthes capita‐ ta*, decomposed faster than the other species studied, although the amounts released of P, K, Ca and Mg were similar among grasses and legumes. Other researchers [13], working with *Ap* 18748 or *Desmodium ovalifolium* CIAT 350 associated with coffee plants, found no differ‐ ences for any legume in N, P and K soil, three years after establishment; unlike [6], who in Australia, in banana plantation with or without *Arachis pintoi* after 5.5 years found signifi‐ cant increases in the association, in terms of organic matter (3.94 vs. 3.71%), N (0.42 vs.

By comparing these costs with the traditional management of weed control in citrus or‐ chards, we found that the costs for these plantations were around US \$ 222 per year. Eco‐ nomic estimates in coffee plantations in Nicaragua [13], mentioned that the relative costs (%) in the establishment and maintenance of the associations were higher in the first two years, compared with the traditional control of weeds, but at that time the use of herbicides was lower between 30-50%. Establishment costs in the three experiments [see 10] fell in the range of US \$ 282 to 623 (the exchange rate in 2001) in terms of inputs applied. Although costs for the establishment of *Arachis pintoi* is higher, this is recovered in about a year and a half or two, with the advantage of having a highly competitive species for weed control and its long persistence in the land, plus inputs of nutrients to the soil as an additional benefit.

*Arachis pintoi* is a promising legume to associate as a cover crop with citrus plantations and other crops of high commercial value, such as bananas, pineapple, coffee and papaya. In the case of the first experiment, *Ap* ecotypes CIAT 18744 and 18748 represent for citrus planta‐ tions area of Veracruz, a better option compared to *Ap* CIAT 17434, due to the slowness of

conditions that found here, which is explained by the higher plant density used.

0.39%); the K, Ca, Mg and Na increased to at 52, 26, 43 and 23%, respectively.

*2.5.2. Second experiment*

**2.6. Conclusions**


PD1 and PD2= Plants sown at 35 and 50 cm within the furrow respectively.

+F: With fertilization (kg/ha: 50 P2O5, 50 K2O, 20 Mg2SO4); and, -F: without fertilization.

\*\*P: Probability level.

**Table 4.** Coverage (%) of plants of *Arachis pintoi* (mean ± standard error) reached five months after planting date according to soil preparation, planting density (D) and the application or no fertilizer (F).


**Table 5.** Changes in the soil with the use of *Arachis pintoi* 16 months after planting.

Moreover, the ecotypes established by seed showed a higher rate of coverage, however, however, these differences in the velocity of establishing tend to disappear as time passes.

#### *2.5.2. Second experiment*

The lower rate of coverage by the accession 17434 was also confirmed [11], on the experi‐ ment developed in this same region comparing four species of forage legumes (*Desmodium ovalifolium*, *Neonotonia wightii*, *Pueraria phaseoloides* and *Stizolobium deerigianum*) associated to a citrus plantation. This slowness in the establishment was also reported in Costa Rica [12]

**Disking 4 8 12 16 20 P\***

0.9641

0.0232

0.3202

PD1+F 19.8±2.04 23.2±2.69 33.0±4.40 76.2±6.25 87.5±3.23

PD1-F 10.5±1.04 17.7±3.17 23.7±10.5 52.5±10.5 70.0±7.90 PD2+F 9.0±0.57 13.2±2.98 20.2±3.75 40.0±12.4 63.7±15.46 PD2-F 8.0±0.71 10.5±1.26 10.5±3.23 26.2±3.14 52.5±9.11

PD1+F 6.0±0.91 4.2±1.31 7.0±1.29 10.2±1.11 11.7±1.08

PD1-F 6.7±1.25 4.5±1.19 3.7±0.48 6.5±0.64 8.2±0.48 PD2+F 6.2±0.47 6.5±0.29 5.7±1.31 7.2±1.43 9.0±1.78 PD2-F 4.2±0.85 4.2±0.94 3.5±0.29 5.7±0.63 6.2±0.85

PD1+F 7.5±0.64 12.0±2.00 7.75±1.25 9.5±0.87 23.7±3.75

PD1-F 8.7±1.10 8.7±1.89 8.7±0.47 20.0±4.56 33.7±5.54 PD2+F 9.0±2.16 4.2±0.48 5.2±0.63 12.2±2.25 26.2±5.54 PD2-F 8.5±0.50 5.0±0.71 10.0±2.38 14.0±3.81 27.5±7.22

**Table 4.** Coverage (%) of plants of *Arachis pintoi* (mean ± standard error) reached five months after planting date

**Soil factors Start End Difference** Organic matter (%) 2.2 2.0 - 0.20 Nitrogen (Kg/ha) 8.9 28 + 19.1 Phosphorus (Kg/ha) 6.0 40 + 34 Potasium (Kg/ha) 86 301 + 215 pH 5.0 5.8 + 0.8

to associate in banana plantations.

Chiseling

52 Soil Fertility

Hoeing

\*\*P: Probability level.

**Treatments Weeks after planting**

PD1 and PD2= Plants sown at 35 and 50 cm within the furrow respectively.

+F: With fertilization (kg/ha: 50 P2O5, 50 K2O, 20 Mg2SO4); and, -F: without fertilization.

according to soil preparation, planting density (D) and the application or no fertilizer (F).

**Table 5.** Changes in the soil with the use of *Arachis pintoi* 16 months after planting.

The coverage obtained with the disking treatment with plants every 35 cm along the furrow, and with or without fertilization are considered acceptable and are superior to those report‐ ed for *Ap* 18748 in coffee plantations of Nicaragua for high plant densities using vegetative material (strips of 3.3 m wide, with furrows 50 cm) and three weedings in the first 90 days [13]. This author reported that at 158 days post seeding, the legume exceeded 60% of ground cover. In Brazil [14], assessed *A*. *pintoi* at plant densities of 8 to 16 plants/linear m, reaching a 50% coverage to 84 and 68 days post seeding, respectively; whether the separation between furrows was 25 or 50 cm. The above percentages indicate superior performance under these conditions that found here, which is explained by the higher plant density used.

Respect to changes detected in the soil properties, the increase in the concentration of N could be attributed to a transfer to the soil of the element present in the leaves of *Arachis pintoi* by the effect of decomposition thereof. In this regard, [15] estimated litter decomposi‐ tion of grasses and legumes, among whom was *A*. *pintoi*. They found that the decomposition of organic matter and nitrogen in leaves of this legume, along with that of *Stylosanthes capita‐ ta*, decomposed faster than the other species studied, although the amounts released of P, K, Ca and Mg were similar among grasses and legumes. Other researchers [13], working with *Ap* 18748 or *Desmodium ovalifolium* CIAT 350 associated with coffee plants, found no differ‐ ences for any legume in N, P and K soil, three years after establishment; unlike [6], who in Australia, in banana plantation with or without *Arachis pintoi* after 5.5 years found signifi‐ cant increases in the association, in terms of organic matter (3.94 vs. 3.71%), N (0.42 vs. 0.39%); the K, Ca, Mg and Na increased to at 52, 26, 43 and 23%, respectively.

By comparing these costs with the traditional management of weed control in citrus or‐ chards, we found that the costs for these plantations were around US \$ 222 per year. Eco‐ nomic estimates in coffee plantations in Nicaragua [13], mentioned that the relative costs (%) in the establishment and maintenance of the associations were higher in the first two years, compared with the traditional control of weeds, but at that time the use of herbicides was lower between 30-50%. Establishment costs in the three experiments [see 10] fell in the range of US \$ 282 to 623 (the exchange rate in 2001) in terms of inputs applied. Although costs for the establishment of *Arachis pintoi* is higher, this is recovered in about a year and a half or two, with the advantage of having a highly competitive species for weed control and its long persistence in the land, plus inputs of nutrients to the soil as an additional benefit.

#### **2.6. Conclusions**

*Arachis pintoi* is a promising legume to associate as a cover crop with citrus plantations and other crops of high commercial value, such as bananas, pineapple, coffee and papaya. In the case of the first experiment, *Ap* ecotypes CIAT 18744 and 18748 represent for citrus planta‐ tions area of Veracruz, a better option compared to *Ap* CIAT 17434, due to the slowness of 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 these costs converting this costs in an effective alternative.

1992). Rainfall was 19% above average during experiment 2 in 1993, but rains in 1996 were

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

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

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‐

m). These plots were divided in two sub plots of 500 m2 (25 m x 20 m), of which one sub plot

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

(50 m x 40 m split in two plots of 1,000 m2


on 29 November, 1991 (winter season), 2


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55

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

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

ly required the elimination of pasture vegetation by machete to ground level.

43% below average for experiment 3 (Figure 3b).

plants [24].

The experimental area was 2,000 m2

*Arachis pintoi* was planted on sub-plots of 500 m2

was fertilised. Three 2,000 m2

(winter, dry and rainy season).
