Effect of intercropping and phosphorous application on the growth and yield of sweetpotato, groundnut and soybean.

Munda, Eliah (2017-03)

Thesis (PhDAgric)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Sweetpotato (Ipomoea Batatas (L) Lam) is among the most important root crops in Mozambique. However, the yield is lower than its genetic potential due to poor soil fertility and poor agronomic practices. Inorganic fertilizers that could contribute to yield increase are too costly hence they are not accessible. One of the feasible option is the use of intercropping with legumes to recapitalize soil fertility and improve yield. In this study the effect of intercropping sweetpotato with groundnut and soybean at three phosphorus (P) levels on soil chemical properties, sweetpotato, groundnut and soybean vegetative growth, yield and sweetpotato nutritional quality was investigated. The study was carried out at Umbeluzi Research Station during the 2013/14, 2014/15 and 2015/16 growing seasons. A factorial design in a split plot arrangement was used. The main plot treatments were; sole sweetpotato, sole groundnut, sole soybean, sweetpotato-groundnut, sweetpotato-soybean, sweetpotato- groundnut- soybean and groundnut- soybean intercropping. The subplot treatments were 0, 20 and 40 kg P ha-1 applied at planting. Sweetpotato- groundnut, sweetpotato- soybean and soybean- groundnut intercropping at 40 kg P ha-1 in the 2015/16 growing season had more soil total nitrogen (N) compared to sole sweetpotato (P=0.038). Soybean-groundnut intercropping at 0 kg P ha-1 in 2013/14 growing season had more Olsen P than sole sweetpotato in all growing seasons (P=0.023). Sweetpotato- groundnut and sweetpotato- soybean had 21 % and 25.3 % more soil CEC respectively than sole sweetpotato at 40 kg P ha-1. Sweetpotato- groundnut and sweetpotato- soybean intercropping at 40 kg P ha-1 had 42.9 % and 32.9 % more CEC than at 0 kg ha-1 respectively (P=0001). All treatments involving legumes in the mix had lower soil pH in 2014/15 and 2015/16 compared to 2013/14 growing seasons. Soybean- groundnut intercropping, sole groundnut and sole soybean had higher soil available potassium (K) compared to sole sweetpotato in 2015/16 growing season (P=0.001). Sweetpotato- soybean intercropping at 20 kg ha-1 had higher sweetpotato main stem length compared to sole sweetpotato. There was no significant difference in sweetpotato main stem length between 20 and 40 kg P ha-1 in the intercropping treatments (P>0.05). Sweetpotato- groundnut intercropping at 40 kg P ha-1 had higher fresh root mass plant -1 compared to sole sweetpotato crop in 2013/14 and 2014/15 growing seasons. Sweetpotato-groundnut- soybean-, sweetpotato-soybean and sweetpotato- groundnut intercropping at 0 and 40 kg P ha-1 had higher number of leaves plant-1 compared to sole sweetpotato. Sole sweetpotato had higher sweetpotato stem diameter compared to sweetpotato- soybean intercropping in 2013/14 and 2014/15 growing seasons. Sweetpotato- groundnut intercropping at 0 and 20 kg P ha-1 had 32.7 % and 58.5 % more total storage root yield compared to sole sweetpotato. (P=0.0001). There was no significant increase in total storage root yield between 20 kg P ha 1 and 40 kg P ha-1 for sweetpotato- groundnut, sweetpotato-soybean intercropping and sole sweetpotato (P>0.05). Highest sweetpotato partial land equivalent ratio of 1.6 was attained on sweetpotato- groundnut intercropping at 20 kg P ha-1. Total storage root yield increased by 33.6 % at 20 kg P ha-1 compared to 0 kg P ha-1. Sweetpotato- groundnut intercropping had 48.3 % more commercial root yield compared to sole sweetpotato at 20 kg P ha-1 (P=0.036). Sweetpotato- groundnut intercropping at 20 kg P ha-1 had 27. 4 % more number of storage roots plant-1 and higher harvest index compared to sole sweetpotato (P=0.001). Sweetpotato- soybean intercropping decreased number of storage roots plant-1 compared to sole sweetpotato in 2014/15 growing seasons (P=0.008). There was no significant difference in the number of storage roots plant-1 between sweetpotato- groundnut intercropping and sole sweetpotato cropping system (P>0.05). Sole sweetpotato at 20 kg P ha-1 had higher storage root diameter compared to sweetpotato-soybean intercropping (P=0.049). Sweetpotato- soybean intercropping had higher storage root length at 20 kg P ha-1 compared to 0 kg P ha-1 in 2013/14 and 2015/16 growing seasons (P=0.027). Total biomass at 20 kg ha-1 was higher than at 0 kg ha-1 in all treatments (P=0.0001). Sweetpotato- groundnut, sweetpotato-groundnut- soybean intercropping and sole groundnut had a significantly higher pod yield at 20 kg P ha-1 than at 0 kg P ha-1 (P=0.005). Groundnut-soybean intercropping had a significantly lower shelled groundnut yield than sweetpotato-groundnut at 20 kg P ha-1 (P=0.017). Percent dry matter content was higher in sole sweetpotato at 40 kg P ha-1 compared to any other treatments involving soybean. Sweetpotato- groundnut and sole sweetpotato at 20 and 40 kg P ha-1 had more percent glucose content in 2014/15 and 2015/16 compared to the 2013/14 growing seasons (P<0.05). Percent starch content at 40 kg P ha-1 was higher than at 0 kg P ha-1 in all growing seasons (P=0.0001). There was a significantly higher β-carotene content in the storage roots in 2015/16 than 2013/14 growing seasons. Sweetpotato- groundnut intercropping at 0 kg P ha-1 had a higher iron (Fe) content in the sweetpotato storage roots compared to any other treatment (P=0.000). Sweetpotato –legume intercropping had more zinc (Zn) content in the storage roots and Zn yield in sweetpotato in 2015/16 compared to 2013/14 growing seasons (P=0.033). Farmers with the same environmentl conditions as where this study was carried out are recommended to intercrop sweetpotato and groundnut at 20 kg P ha-1. Key words: intercropping, legumes, micronutrient deficiency, nutritional quality, sweetpotato.

AFRIKAANS OPSOMMING: Patats (Ipomoea Batatas (L) Lam) is een van die belangrikste wortelgewasse in Mosambiek. Die opbrengs wat verkry word deur kleinskaalse boere is egter laer as die genetiese potensiaal as gevolg van swak grondvrugbaarheid en swak verbouiingspraktyke. Anorganiese bemestingstowwe wat moontlik kan bydra tot opbrengsverhogings is te duur en bemoeilik toegang daartoe. Een moontlikheid is om gebruik te maak van tussengewasverbouing met peulplantgewasse om grondvrugbaarheid te herstel en opbrengs te verhoog. In hierdie studie is die invloed van tussenverbouing van patat met sojabone en grondbone by drie fosfaatpeile (P) op grond se chemiese eienskappe, patat,grondbone en sojabone se vegetatiewe groei, opbrengs en voedingskwaliteit ondersoek. Die studie is uitgevoer by die Umbeluzi navorsingstasie gedurende die 2013/14, 2014/15 en 2015/16 groeiseisoene. ‘n Faktoriaal eksperiment gereël as ‘n gesplete perseel uitleg is in hierdie studie gebruik. Die hoofperseelbehandelings vir die studie op grondchemiese eienskappe was sewe gewaskombinasies naamlik suiwer patat, suiwer grondboon, suiwersojaboon, patat-grondboon, patat-sojaboon, patat-grondboon-sojaboon en grondboon-sojaboon tussenverbouing. Die subperseelbehandelings was 0, 20 en 40 kg P ha-1 wat toegedien is met plant. Patat-grondboon, patat-sojaboon en sojaboon-grondboon tussenverbouing by 40 kg P ha-1 in die 2015/16 groeiseisoen het die totale grondstikstof (N) verhoog vergeleke met suiwer patat (P=0.038). Sojaboon-grondboon tussenverbouing teen 40 kg P ha-1 het minerale N inhoud van die grond betekenisvol verhoog vegeleke met die suiwer patat persele (P=0.01). Sojaboon-grondboon tussenverbouing teen 0 kg P ha-1 in die 2013/14 seisoen het meer Olsen P gehad as by dieselfde P vlak in al die groeiseisoene (P=0.023). Patat-grondboon en patat-sojaboon kombinasies by 40 kg P ha-1 het katioon uitruil vermoë (KUV) met 42.9% en 32.9% respektiewelik verhoog vergeleke met suiwer patat. Alle behandelings met peulgewasse in die mengsel het grond pH in 2014/15 en 2015/16 seisoene verlaag vergeleke met die 2013/14 seisoen. Sojaboon-grondboon tussenverbouing, suiwer grondboon en suiwer sojaboon het hoër grondbeskikbare kalium (K) in die grond gelaat na oes as suiwer patat in 2013/14 (P=0.001). Patat-sojaboon tussenverbouing teen 20 kg P ha-1 het hoofstamlengte van patats betekenisvol verhoog vergeleke met suiwer patat. Daar was nie betekenisvolle verskille in patatstamlengtes tussen 20 en 40 kg P ha-1 in die tussenverbouingsbehandelings nie (P<0.05). Patat-grondboon tussenverbouing by 40 kg P ha-1 het vars wortelmassa plant-1 verhoog vergeleke met suiwer patat in die 2013/14 en 2014/15 groeiseisoene. Patat-grondboon-sojaboon, patat-sojaboon en patat-grondboon tussenverbouing by 0 en 40 kg P ha-1 het die aantal blare plant-1 verhoog vergeleke met suiwer patat. Suiwer patat het egter ‘n groter stamdeursneë gehad vergeleke met patat-sojaboon tussenverbouing in beide die 2013/14 en 2014/15 groeiseisoene. Patat-grondboon tussenverbouing by 0 en 20 kg P ha-1 het totale stoorwortelmassa betekenisvol met 32.7% en 58.5% onderskeidelik verhoog vergeleke met suiwer patat by dieselfde P vlakke (P=0.0001). Daar was geen betekenisvolle toename in totale stoorwortelmassa tussen 20 en 40 kg P ha-1 in patat-grondboon, pata-sojaboon tussenverbouingstelsels en suiwer patat stelsels nie (P>0.05). Die hoogste patat gedeeltelike ekwivalent land verhouding (LER) was 1.6 vir patat-grondboon tussenverbouing by 20 kg P ha-1. Totale stoorwortelmassa het met 33.6% vermeerder by 20 kg P ha-1 vergeleke met 0 kg P ha-1. Patat-grondboon tussenverbouing het kommersiële wortelproduksie met 48.3% verhoog vergeleke met suiwer patat stelsels (P=0.036). Patat-grondboon tussenverbouing by 20 kg P ha-1 het die aantal stoorwortels plant-1 met 27.4% verhoog asook die oesindeks verhoog vergeleke met suiwer patat stelsels (P=0.0001). Patat-sojaboon tussenverbouing het die aantal stoorwortels plant-1 verminder vergeleke met suiwer patat in die 2014/15 groeiseisoen (P=0.008). Daar was geen betekenisvolle verskille tussen die aantal stoorwortels plant-1 in patat-sojaboon tussenverbouing en suiwer patat verbouingstelsels nie (P>0.05). Suiwer patat stelsels by 20 kg ha-1 het die stoorwortel deursneë verhoog vergeleke met patat-sojaboon tussenverbouing (P=0.049). Patat-sojaboon tussenverbouing het stoorwortellengte verhoog by 20 kg P ha-1 vergeleke by 0 kg P ha-1 in die 2013/14 en 2014/15 groeiseisoene (P=0.027). Totale biomassa by 20 kg P ha-1 was betekenisvol hoër as by 0 kg P ha-1 by alle verbouingsbehandelings (P=0.0001). Patat-grondboon, patat-grondboon-sojaboon tussenverbouing en suiwer grondboon het betekenisvol meer peule gelewer by 20 kg P ha-1 as by 0 kg P ha-1 (P=0.005). Grondboon-sojaboon tussenverbouing het ‘n betekenisvolle laer gedopte grondboon opbrengs gelewer as patat-grondboon tussenverbouing by 20 kg P ha-1 (P=0.017). Persentasie droëmateriaalinhoud van patatwortels het verhoog in suiwer patat stelsels by 40 kg P ha-1 vergeleke met enige ander behandeling wat sojabone ingesluit het. Patat-grondboon en suiwer patat stelsels het ‘n hoër persentasie glukose inhoud in patatwortels tot gevolg gehad by 20 en 40 kg P ha-1 in die 2014/15 en 2015/16 groeiseisoene vergeleke met die 2013/14 groeiseisoen (P<0.05). Persentasie styselinhoud by 40 kg P ha-1 was hoër as by 0 kg P ha-1 in al die groeiseisoene (P=0.0001). Daar was ‘n betekenisvolle hoër β-karoteen inhoud in die stoorwortels in 2015/16 as in die 2013/14 seisoen. Patat-grondboon tussenverbouing by 0 kg P ha-1 het meer yster (Fe) in die patat stoorwortels opgelewer vergeleke met enige ander behandeling(P=0.0001). Patat-peulplant tussenverbouing het ‘n hoër sink (Zn) inhoud van stoorwortels en Zn opbrengs in patat in die 2015/16 seisoen tot gevolg gehad as in die 2013/14 groeiseisoene (P=0.033). Boere wat boer in dieselfde omgewingstoestande as waar hierdie studie uitgevoer is word aangeraai om tussenverbouiing met patat en grondbone uit te voer met toediening van 20 kg P ha-1. Sleutelwoorde: mikro-element tekorte, patat, peulplante, tussenverbouing, voedingskwaliteit

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