RESEARCH WORK

 

 

 

Effect of cutting interval and nutrition management in mulberry [Morus alba (L.)]. I. Forage production

 

 

 

Gertrudis Pentón-Fernández1, Giraldo J. Martín-Martín1, Ramón Rivera-Espinosa2, Gloria M. Martín-Alonso2, Rey Machado-Castro1 and José A. Herrera-Altuve2

1Estación Experimental de Pastos y Forrajes Indio Hatuey, Universidad de Matanzas, Ministerio de Educación Superior Central España Republicana, CP 44280, Matanzas, Cuba
2Instituto Nacional de Ciencias Agrícolas, Mayabeque, Cuba
E mail: gertrudis@ihatuey.cu; tulypenton@gmail.com

 

 

 


ABSTRACT

A study was conducted in order to evaluate the cutting intervals (30, 60 and 90 days) and the nutrition management in mulberry: without mineral fertilizers or intercropped and AMF-inoculated Canavalia ensiformis (F0); mineral fertilization at a rate of 150 and 75 kg ha-1 of N and K2O per season (MF), respectively; and intercropped and AMF-inoculated C. ensiformis (CeAMF). The design was randomized blocks with factorial arrangement, and the soil is classified as lixiviated Ferralitic Red. In the rainy season, the highest yields were obtained with CeAMF and cutting every 90 days (between 10,99 and 6,85 t DM ha-1), and in the dry season this indicator was higher in MF (between 3,56 and 2,52 t DM ha-1). The edible biomass production per cutting at 90 days showed differences among treatments in favor of MF in the first cutting and of CeAMF in the second cutting. CeAMF with the 90-day interval reached a proportion of leaves higher than the population mean in the rainy season, unlike the dry season. The CP yield in the rainy season was higher in MF with the 60- and 90-day intervals, and in CeAMF in the 90-day interval. It is concluded that the cutting interval every 90 days was the best, and that it was feasible to intercrop AMF-inoculated C. ensiformis in the rainy season. The season determined the amount of forage and crude protein production, which was three times higher in the rainy season.

Key words: fertilizer application, Canavalia ensiformis (L.), inoculation, arbuscular mycorrhizae.


 

 

INTRODUCTION

Mulberry (Morus alba L.) is an outstanding species for its high edible biomass yields, digestibility, acceptability, nutritional value and perenniality when cut (Martín et al., 2007). Likewise, the tigreada variety is considered among the ones with the best productive response under the edaphoclimatic conditions of Cuba, in areas without irrigation (Martín, 2004). The main results with this variety emphasize its use as feedstuff for rabbits, pigs, sheep and cattle (Martín et al., 2013).

The cutting interval is one of the determinant factors in the forage production of mulberry, and is influenced, in turn, by fertilization and season (Martín et al., 2013). The reports found in the scientific literature about this aspect have been generated in monocrop plantations with cutting intervals of 45, 60, 75, 90 and 120 days (Martín, 2004; Rojas, 2005; García et al., 2011).

Thus, Martín et al. (2002) studied forage yields of mulberry with different cutting intervals and obtained the highest edible dry mass productions with 120 and 90 days, respectively.

Martín et al. (2000) observed that, although with cutting intervals of 45 and 60 days higher proportions of edible biomass were obtained with regards to the total biomass (85 and 74 %, respectively), the absolute values of edible biomass were higher with the 90-day interval; with which Almeida and Fonseca (2002) coincide.

Regarding the management of mulberry nutrition, it is known that the high doses of fertilizers required by this crop imply high production costs (Elizondo, 2007), and in order to reduce such inputs it is important to evaluate practices that have been effective in other crops, such as the use of green manures (CIDICCO, 2004) and mycorrhizal inoculants (Riera, 2002; González, 2014).

The studies conducted by Martín (2009) and García (2014) showed the advantages of the joint management of arbuscular mycorrhizal fungi (AMF) and jack bean [Canavalia ensiformis (L.)], as precedent green manure, not only to increase the biomass and nutrient recycling associated to the incorporation of jack bean, but also as a way to achieve effective mycorrhization and increase the agricultural yield of the previously planted cash crops.

Although there is some information about intercropped mulberry plantations, it is related to cash crops (Srinivas, 2005), and no results of association with green manures, or of the evaluation of their potential as a way to inoculate mulberry plantations with AMF, have been found.

For all these reasons, the objective of this research was to determine the possibility of intercropping the M. alba plantations with AMF-inoculated C. ensiformis, in interaction with the cutting interval and season.

 

MATERIALS AND METHODS

Geographical location. The trial was conducted during two years, in areas of the Research Station Indio Hatuey, located between 22º 48' and 7" North latitude, and 81º and 2' West longitude, at 19,01 m.a.s.l.; in the Perico municipality, Matanzas province, Cuba.

Edaphoclimatic characteristics. The soil corresponds to the genetic type lixiviated Ferralitic Red, according to the criteria expressed by Hernández et al. (2015), and with the classification Lixic, Euthric, Rhodic Ferralitic Nitisol (FAO, 2014). The topography is flat, with slope from 0,5 to 1,0 %, and the depth to the limestone rock is 1,50 m.

According to the initial chemical analysis of the soil at the depth of 0 to 20 cm (table 1) and the tables of agrochemical interpretation (Cancio 1982; Paneque and Calaña, 2001), the pH values and the concentration of exchangeable Ca and Mg are typical of these soils, and the content of exchangeable K is low. The available P concentration is low, and shows a moderate organic matter content.

The climate in the experimental stage was characterized by an annual rainfall mean of 1 487 mm and 19 % of the rainfall occurred in the dry season, which is framed between November 15 and April 15. The mean annual temperature value was

23,6 ºC and varied between 25,90 ºC and 21,20 ºC in the rainy and dry season, respectively. These values are in correspondence with the averages of the last 20 years (1 393,3 mm of mean annual rainfall): 1 120,25 mm and 25,95 ºC in the rainy season, and 273,05 mm and 21,65 ºC in the dry season (Meteorological Station Indio Hatuey, CITMA).

Description of the trial. The study was conducted per season. The planting frame of mulberry was 0,50 x 1,00 m, with a density of 20 000 plants ha-1. The experimental plots measured 24 m2 and had 48 plants; for the calculation 12 age-homogeneous plants were used, located at the center of the plots, with an area of 6 m2.

The experimental design was randomized blocks with factorial arrangement and four replications. The treatments were:

Factor: cutting interval (A): three cutting intervals were evaluated: 30, 60 and 90 days.

Factor: nutrition management (B): without mineral fertilizers or intercropped and AMF-inoculated jack bean (without MF or CeAMF); mineral fertilization (MF) 150 and 75 kg ha-1 of N and K2O per season, respectively; intercropped jack bean inoculated with Glomus cubense at the moment of planting in each season.

The cutting intervals in each season started and ended in unison. The cutting dates for each interval were: 30 days (every 1st of each month of the year), 60 days (the 1st every two months since July), and 90 days (the 1st every three months since August).

The fertilizers were manually applied, on day seven of May and November, on the soil surface and on the stem basis; the porters used were urea (46 %) and potassium chloride (60 %). No fertilizer with P was applied, based on the low requirements of the mulberry crop (Cifuentes and Sohn, 1998) and the mean initial concentration of available P at the soil depth of 20 cm, equivalent to 99,62 kg ha-1.

Jack bean was manually planted, in each season. The planting density was 25 000 plants ha-1 (with a frame of 0,4 x 1,0 m), intercropped between the mulberry rows, at a distance of 0,50 m with regards to the furrows and with 60 plants in each plot.

The jack bean seeds were covered, through the method established by Rivera et al. (2006), with 0,15 g of inoculant per seed in each season. The mycorrhizal inoculant consisted in spores and other propagules, and was prepared by the EcoMic® technology (Fernández et al., 2000) in the biofertilizers and plant nutrition department of the National Institute of Agricultural Sciences, with a titer of 25 pores per each gram of inoculant as minimum. The jack bean cutting was performed at 60 days; the aerial biomass was fractionated into equal parts and placed as mulch around the mulberry in a proportion of 1,25 plants of jack bean per each mulberry plant. The weeding was maintained throughout the experimental period; and the criterion of not applying irrigation was assumed, in correspondence with the reality of most farming exploitations.

 

Measurements

Statistical analysis. The data distribution normality was verified in all the variables through the modified Shapiro Wilk test, and the variance homogeneity was verified using Levene's test. The mean discrimination was made by Duncan's (1955) multiple comparison test at p d» 0,05.

The effect of the season and year was evaluated through the analysis of paired samples in each treatment and later t-test (Steel and Torrie, 1992).

The comparison was made between the cutting moments with the 90-day interval, by the analysis of the confidence limits (± Z1. SE x), for a significance of 0,05. The statistical pack used was Infostat 2008 (Di Rienzo et al., 2008).

 

RESULTS AND DISCUSSION

Indicators of biomass yield. There were significant effects of the interaction between the factors cutting interval and nutrition management (table 2). The best treatments in any of the seasons were associated with the 90-day cutting interval, and this obeys the fact that mulberry describes a growth and development curve that can reach, at the ages from 90 to 105 days, the highest biomass yield (Pentón et al., 2007).

In the rainy season, the highest yield in the 90-day cutting interval were obtained with the intercropped and AMF-inoculated jack bean; while in the dry season they were also in favor of the mineral fertilization.

There was no competition effect of jack bean with mulberry in the 90-day cutting interval; but it did occur in the 60-day interval (fig. 1).

Willey et al. (1986) stated, about the interspecies behavior, that the yield increase of the mulberry associated with legumes depends on the species differing in their needs of resources for growth. The effect of competition is minimized when the cutting moment of mulberry and the planting and harvesting of the intercropped species are adjusted in benefit of the main crop, which was satisfactory in this study in the 30- and 90-day intervals, and reinforces the report in this regard by Hadimani et al. (2004) and Srinivas (2005) about the possibilities of intercropping the mulberry plantations with short-cycle crops.

In the dry season there was no influence of the AMF-inoculated jack bean on the mulberry yield, which suggests that the possibilities for a successful association between the crops decreased; this could have been related to the lower rainfall that characterizes this season, which reduces the access of plants to the soil nutrients, and, thus, a decrease can occur in the growth of jack bean and its benefits. The reproduction of mycorrhizal propagules under such conditions could have been lower, aspect that was approached by Martín (2009) when studying the AMF-inoculated jack bean as precedent crop.

The production of edible biomass per cutting in the most productive interval, the 90-day one, showed differences in the treatments of mineral fertilization and intercropped and AMF-inoculated jack bean (fig. 2).

In the first cutting of the rainy season, the mineral fertilization guaranteed higher production of edible biomass, compared with the treatment with jack bean; while in the second cutting, the effects of jack bean were higher and it caused that in the seasonal accumulated value this was the treatment with higher biomass production. Such performance suggests that in the first cutting jack bean was growing along with mulberry; as a possible cause the capacity of jack bean to reproduce mycorrhizal propagules can be mentioned (Martín, 2009; García, 2014), which in this study seemingly guaranteed the mycorrhization of mulberry. The mulching of the jack bean biomass and its later decomposition (González, 2002) could have caused a higher conservation of soil humidity, the control of weeds and the stimulation of the biological activity.

Because the treatment with jack bean did not guarantee a productive stability and the propitious conditions for growth in the rainy season were not utilized, it was necessary to complement with fertilizers, at least for the first cutting of that season.

In the dry season, the treatment that received mineral fertilization had higher influence on the biomass production of the first cutting.

Leaves/fresh stems proportion of mulberry. In all the treatments the leaf/fresh stem proportion reached higher values than 1,2 (table 3), which are in correspondence with the reports for this species. In that sense, Iglesias (2003) stated that the fact that in the edible biomass of mulberry the leaves have the highest proportion makes this a forage plant of higher quality than conventional forages.

There was significant effect of the interaction between the factors cutting interval and nutrition management. The treatment of mineral fertilization with the 60-day interval was among those of higher leaf proportion and tripled the proportion of fresh stems. Coincidentally, Martín et al. (2007) observed that the leaf proportion in the total biomass significantly decreased with the increase of the cutting interval.

In the 60-day cutting interval, the highest leaf proportion in the treatments with mineral fertilization explains, to a certain extent, the superiority of the edible biomass yield.

The intercropped and AMF-inoculated jack bean, in the 90-day interval (of higher forage yield in the rainy season), reached a leaf proportion that exceeded the population mean in the rainy season, unlike the dry season; this suggests that in the rainy seasons, the edible biomass that is obtained with this nutrition management practice is characterized by a significant increase in the leaf proportion, which allows to infer an increase in the forage quality.

The increase of leaf proportion in the rainy season, compared with that of the dry season, was a general trend in all the evaluated treatments and years, and differs from the results obtained by Martín et al. (2007), who observed that the leaf proportion in the total biomass varied in favor of the dry season in 9 and 11 % in the 60- and 90-day intervals, respectively.

Crude protein yield in the edible biomass of mulberry. The crude protein yield in the rainy season was higher in the treatments with mineral fertilization in the 60- and 90-day cutting intervals, and with intercropped and AMF-inoculated jack bean in the 90-day interval (table 4). In the dry season the highest value was associated to the 90-day treatment with mineral fertilization.

This corroborate the reports by García (2003), who stated that among the factors of higher influence on the protein yield are season and cutting interval, followed by nitrogen and potassium fertilization.

According to the results, it is concluded that the 90-day cutting interval of mulberry was the best, and that it was feasible to intercrop AMF-inoculated jack bean in the rainy season. The season determined the amount of the forage production and crude protein, and in the rainy season it was three times higher than in the dry season. Likewise, in the rainy season and in the 90-day interval mulberry responded better in terms of edible biomass production to chemical fertilization in the first cutting and to intercropped and AMF-inoculated jack bean in the second cutting.

To study the combination of these nutrient supply ways, which are related to the demand of inputs by the crop and to the form of inoculation of the arbuscular mycorrhizal fungi, is recommended.

 

 

 

Received: January 4, 2015
Accepted: December 23, 2015