RESPONSE OF COWPEA PLANTS (Vigna unguiculata (L.) WALP.) TO SOME BIOSTIMULANTS AND ORGANIC NUTRIENTS DURING LATE SUMMER SEASON.

El-S. L. El-S. Fathy, *and M. M. El-Hamady**                                    

*Vegetable Department, Horticulture. Research Institute, Agriculture Research Center, Cairo, Egypt.

** Plant Production Department, Efficient Productivity Institute., Zagazig University, Egypt.

ABSTRACT

Two field experiments were conducted during 2005 and 2006 at El-Baramon Experimental Farm, El-Dakahllia Governorate, Hort. Research Institute. In order to study response of cowpea plants El-Balady  cv.  grown during late summer season to foliar feeding with some biostimulants (amino acids– seaweed extracts) and organic nutrients,(potassium borate citrate, organic boron,zinc citrate, calcium citrate, NPK-Humate)besides to NAA, on growth, mineral composition and yield and its components towards, maximizing its productivity under such season condition.

The results could be summarized as follows:

The applied treatments were significantly differed among them and were superior the control in all growth parameters, mineral concentration (NPK and Ca) in leaves, seed yield and its components during the two seasons.

The best ones in diminished order were KB-citrate NPK-humate, NAA, amino acids, B-EA (organic boron), seaweed extracts, Zn-citrate and at least Ca-citrate, those increased their plants, dry weight and total seed yield increased over the control by (35.67%,43.9%), (26.79% ,35.01%), (26.36% ,35.1%), (24.66% ,30.8%), (24.63% ,32.3%), (17.98% ,27.5%) ,(16.64%,25.8%)  and (5.73%,20.5%) means of the two seasons, respectively. Also, these treatments resulted in significant increase in concentration of N,P,K and Ca in leaves compared with the control one.

It could be sprayed late summer grown cowpea plants with potassium  borate citrate (3ml/L) or NPK-humate (2.5ml/L) to obtain the best growth and mineral concentration and the maximum total seed yield.

Key words: Cowpea plants (Vigna unguiculata (L.)WALP.), biostimulants, organic nutrients, summer season.

INTRODUCTION

In recent years, stressful high temperature prevails in Egypt during late summer season. This frequently cause severe depression in different performances of vegetable crops including cowpea (Wein et al., 1993; Fathy and Farid, 2000; Fathy and Khedr, 2005 b).

At the physiological and metabolical basis high temperature induces serious internal disordered case and drastic events of bioassimilates, hormones and nutrients shortage and imbalances and lacking of their supply into reproductive sinks; as well as induces serious injurious oxidative stress. This case lead to serious agronomical problems of poor fruit setting, abscission of fruits and low productivity (Wien and Zhang, 1991, Huberman et al., 1997; Fathy and Farid, 2000, Khedr et al., 2004).

In addition, thermotolerance and thermoinjury known to be associated with the internal ions level that play a role in the activation of the transporter enzymatic system (H-ATP-ase) membrane pump and certain H⁺, K⁺ and Ca⁺⁺ balance leading to stress protection processes and responses (Palta, 1990).

Also, with the capability to activate the antioxidantal defensive enzymatic systems against high temperature inducable degradable oxidative stress (Dicknson et al., 1991 and Cakmak and Marschner, 1992).

Based on the above mentioned information and the cited literature, the present work aimed to ameliorate the propable destructive effects of high temperature condition, restore the plants into normal function and enhanced productivity case. This suggested to be achieved by application and then identification the effect of promising natural biostimulants and organic nutrients, i.e. amino acids, seaweed extracts, NPK- humate complex, K-B citrate, Ca-citrate, Zn-citrate, and B-EA (boron organocomplex) as well as NAA on different performance of cowpea plants.

Herein of value to cited the relevant information about these treatments Franco et al. (1998) showed that foliar spraying of amino acids improved fruit yield and quality of tomato. Fathy and Khedr (2005a) illustrated that the frequent foliar feeding with amino acids, Zn-citrate and phytoextract (yeast) individually or in combination was considerably recovered the biotic stressed tomatoes due to their beneficial effects on the metabolic potential for synthesis of amino acids, protein, sugars, carbohydrates also to their antioxidant defensive function including synthesis of carotenoids and phenols also enhancing efficient on uptake of N, P and K and at least corresponding these responses with normal growth and high fruit yielding capacity.

Many different effects have been reported as a result of the application of seaweed extracts, including enhanced crop yield, increased uptake of inorganic nutrients from the soil, improved different growth aspects, induced resistance to stress conditions(biotic and a biotic ones). Such extracts know to exhibit different regulatory, and defensive effects through elicitation and singling of different physiological and metabolical processes (Metting, 1990; Blunden, 1991). Whapham et al. (1993) used alkaline extract of Ascophyllum nodsum either as foliar or soil application, this result in improving growth and chlorophyll content of treated plants El-Aidy et al. (2002) found that, foliar spraying of different commercial formulations of seaweed extracts (Maxicrop and ASCO) considerably improved growth, N and P content of leaves, early and total yield of sweet pepper. Similar results were obtained by using foliar feeding of brown algae (Ascophyllum nodsum) (Goemar) (Klarzynski et al., 2006 and Zdravkovic et al., 2006) on bean.

Meanwhile it was demonstrated that, humic acid, alone and/or its, formulations in form of mineral organocomplex applied through foliar or root feeding resulted in considerable improvement in different crops growth, mineral contents and bioconstituents  and productivity.

On the other hand, it was well known that, some nutrients (K, Ca, Zn and B) specially in organic chelated form are efficiently participated in the internal processes associated with protection against high temperature stress condition also, that their foliar spraying is considerably improved different performances of the stressed plants (Franco et al., 1998; Wenyi et al., 1999;  Khedr et al., 2004 ; Fathy and Khedr, 2005 a and b).

In addition, it was found that foliar application of NAA especially during high temperature condition is used as a standard practice for reducing abscission of reproductive organs, improving fruit set and productivity also enhancing growth and mineral content of different crops (Pressman et al., 1998 with pepper; Singh and Awasthi, 1998 with Vigna radiate; Resmi and Gopalakrishnan, 2004 with Vigna unguiculata ( L.) Walp .

Therefore, the aim of the present study to investigate the response of cowpea plants (Vigna unguiculata (L.) Walp.) to some biostimulants and organic nutrients during late summer season.

MATERIALS AND METHODS

Two field experiments were performed at El-Baramon Experimental Farm, El-Dakahllia governorate, Horticulture Research Institute during two summer successive seasons of 2005 and 2006 on cowpea plants. This work aimed to study the effect of some biostimulants and organic nutrients on different performances of this crops under high temperature stressful conditions of late summer season towards maximizing its productivity under such condition.

May,2^nd  seeds of cowpea El-Balady cv. were sown in hills on one side ridge of 5m long and 0.6m wide and 0.25m between hills. After emergence the plants thinned leaving one plant per hill. The plot area was 9m²with planting density of about 26600plant /fed.

These plants were sprayed 3 times (20 day after sowing and again every 20 day) with the solution of the following treatment :-

1-Amino acids (35.0% w/v total amino acids) from biological origin, commercially named Mëgfol introduced from Valagro Comp., Italy., registered in Egypt as biostimulants with number 4827, applied at concentration of 1.5ml/L.

2-Seaweeds, natural phytoextract of Ascophyllum nodosum a brown algae introduced from Goëmar Laboratoires, France, registered in Egypt as biostimulant (Goëmar BM86) with No. 5468. It contains more than 17 essential amino acids (5738µ mol / L), vitamins (40 mg / kg) phytohormons (200 mg / L), Betaines (140 mg / L), polysaccharides (50% DM), also enreached with N, Mg, S, B and Mo, applied at concentration of 2.5ml/L.

3-NPK-Humate: 10% humic acids + 8% (N) + 8%( P₂O₅) + 8%( K₂0) registered with NO. 5709 Horticulture. Research Institute, applied at concentration of 2.5ml/L.

4-Potassium borate citrate (35% K₂0 , 5% B),  formulation of Hort. Res. Inst. applied at concentration of 3.0ml/L.

5-Calcium citrate (Ca-cit.) 25% Ca, registered No. 5713 Hort. Res Inst., applied at concentration of 5ml/L.

6-Zinc citrate (Zn cit.) 12% Zn, registered No. 5714, Hort. Res Inst., applied at concentration of 1.5ml/L.

7-Organic boron (B-EA) (Solbor) 8% B, from Hort. Res Inst., applied at concentration of 1ml/L.

8-NAA, from Alfrut commercial formulation (3.5% pure NAA w/v), from SIFO, Italy applied at concentration of 10mg/L.

9-Control, only sprayed with water.

All cultural practices were performed as recommended by Hort. Res Inst.

Randomized complete block design was adopted and the treatments were replicated three times.

At 75 days from sowing 5 plants from each plot were taken and No. of leaves, No. of shoots, fresh and dry weight (gm) were recorded and calculated per plant. Samples of fully expanded mature leaves were taken from each plot 10 days after the last spray for chemical analysis of N, P, K and Calcium. Nitrogen, P and K were analyzed and determined according to methods of Horneck and Miller (1998), Sandell (1950) and Horneck and Hanson (1998), respectively. Calcium was analyzed using atomic absorption method.

Yield and its components: number of pods/plant and number of seeds/pod were recorded from the cumulative harvestings of ten marked plants of each plot. The dried seeds weight determined on plot basis then, seed yield (gm)/plant and total seed yield (ton)/fed. were calculated.

All data were statistically analyzed according to (Snedecor and Cochran ,1980).

Also, data of air temperature(C^o) and relative humidity(%) as well as of soil analysis during 2005 and 2006 are presented herein in Tables 1 and 2.

Table (1): Means monthly air temperature(C^o) and relative humidity (%) at El-Dakahlia Governorate, during 2005 and 2006.

Source: Mansoura Meteorological  Station.

Table 2 : Mechanical and chemical analysis of the experimental soil during 2005 and 2006.

The experimental soil was analyzed by using standard method described by Page (1982).

RESULTS AND DISCUSSION

1- Vegetative Growth:

The data in Table 3 prove that, all the applied foliar sprays of biostimulants and minerals in organic form were significantly increased number of leaves and shoots, fresh and dry weight of their plants in comparison with the control one during the two seasons. The most stimulatory and potent effects in diminished order were of KB-citrate followed by NPK-humate and NAA, then B-EA and amino acids, Zn-citrate and seaweed extracts and at least Ca-citrate respectively.

These treatments increased dry weight of plants relative to the control one by 35.67%, 26.79%, 26.36%, 24.66%, 24.63%, 17.98%, 16.64%, and 5.73% (mean value of the two seasons), respectively.

These results were inconsistent with those obtained by Wenyi et al. (1999); Fathy et al. (2003) and Khedr et al.( 2004) for foliar feeding with K, Ca, Zn, and B under stress condition; Neri et al., 2005, Padem et al., 2007, El-Aidy et al., 2002 (humic acids and seaweed extracts), Franco et al., 1998 (amino acids); Resmi and Gopalakrishnan, 2004 (NAA). Seemingly the applied treatments achieved growth increments in dry weight ranged from 16.6 to 35.6%, except that of Ca-citrate 5.7%, also, some treatments such as KB-cit. were superior NAA (the standard synthetic phytoregulator) or some what equal it NPK-humate, B-EA and amino acids. This to far extent proved high stimulatory effects for these treatments).

Herein, the lowest growth behavior of untreated cowpea plants proved that, these plants, were to certain extent stressed by high temperature. This could be due to