<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0377-9424</journal-id>
<journal-title><![CDATA[Agronomía Costarricense]]></journal-title>
<abbrev-journal-title><![CDATA[Agron. Costarricense]]></abbrev-journal-title>
<issn>0377-9424</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Costa Rica. Colegio de Ingenieros y Agrónomos. Ministerio de Agricultura y Ganadería]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0377-94242016000200147</article-id>
<article-id pub-id-type="doi">10.15517/rac.v40i2.27394</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Resistencia mecánica del suelo a la penetración de raíces y forma de la raíz reservante de la batata a partir del descriptor de Huamán]]></article-title>
<article-title xml:lang="en"><![CDATA[Soil mechanical resistance to root penetration and shape of the reserve root of sweet potato from the Huaman descriptor]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Pérez]]></surname>
<given-names><![CDATA[Maiby]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[García]]></surname>
<given-names><![CDATA[Auris]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Paredes]]></surname>
<given-names><![CDATA[Allen]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Luna]]></surname>
<given-names><![CDATA[Juan]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Madriz]]></surname>
<given-names><![CDATA[Petra]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Central de Venezuela Facultad de Agronomía ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>VE</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2016</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2016</year>
</pub-date>
<volume>40</volume>
<numero>2</numero>
<fpage>147</fpage>
<lpage>159</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S0377-94242016000200147&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S0377-94242016000200147&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S0377-94242016000200147&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[ResumenSe estableció un ensayo para determinar la influencia de la resistencia mecánica a la penetración de raíces (RP), en un suelo afectado por la labranza y por la distancia de siembra, sobre la forma de la raíz reservante del cultivo batata (Ipomoea batatas (L.) Lamb). El diseño del experimento se basó en un arreglo en franjas, donde los sistemas de labranza (SL) fueron asignados a las parcelas grandes y las densidades de siembra (DS) a las franjas. Los SL consistieron en: 1) labranza vertical profunda con cincel y 3 pases de rastra (LC); 2) profunda con arado de disco y 3 pases de rastra (LA); 3) media con 3 pases de rastra de disco (LCo); y 4) mínima con un pase de rastra de disco (LM). Con 4 profundidades de trabajo de 18, 23, 12 y 7 cm, respectivamente. Las DS fueron de 0,25 cm (D1) y 0,15 cm (D2) en la hilera. La RP fue superior en los estratos del suelo a profundidades de 5 a 15 y 15 a 25 cm en los tratamientos de LM, (44 y 37%, respectivamente), respecto al promedio observado en el resto de los tratamientos en los estratos mencionados. Hubo escasa diferenciación entre los sistemas de labranza media y profunda (LCo, LC, LA) para RP. Se encontraron formas redondeadas preferiblemente en los tratamientos de LA; elíptica y redonda, elíptica bajo LC; y redonda y redonda elíptica en LCo y LM. No se observó una mayor restricción del crecimiento longitudinal de la raíz del cultivo en el suelo con mayor dureza bajo los tratamientos de LM. Esto en parte explicado a partir de los valores no limitantes a la penetración de raíces (&lt; 2 MPa) del suelo en los diferentes tratamientos.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[AbstractA study was carried out in order to evaluate the influence of mechanical resistance to root penetration (PR), in a soil affected by tillage and seeding distance, on the shape of the reserve root of a sweet potato crop (Ipomoea batatas (L.) Lamb). Experimental design was based on a strip plot arrangement, where big lots were assigned to tillage systems (TS) and seeding density (SD) to strips. The TS consisted of: 1) deep vertical tillage with chisel (CT); 2) tillage with disc plow (DT); 3) conventional tillage with 3 harrow passes (CoT); and 4) minimum tillage with one harrow pass (MT). With 4 tillage working depths of 18, 23, 12 y 7 cm, respectively. The SD were of 0.25 cm (D1) and 0.15 cm (D2) on the crop row. RP average was higher at deeper soil layers for MT treatments (5-15, 15-25 cm) by 44 and 37%, with respect to that observed at same soil layers in the rest of tillage systems. There was scant difference between medium and deep tillage systems (CoT, CT, DT) for PR. The shape of the reserve root was variable, a rounded shape found mostly in MT treatments, contrary to that expected considering the greater restriction to longitudinal root growth on soils with higher strength under MT. This partly explained by the non-restrictive values to soil root penetration (&lt; 2 MPa) found for the different treatments.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Forma]]></kwd>
<kwd lng="es"><![CDATA[raíz reservante]]></kwd>
<kwd lng="es"><![CDATA[labranza]]></kwd>
<kwd lng="es"><![CDATA[densidades de siembra]]></kwd>
<kwd lng="en"><![CDATA[Shape]]></kwd>
<kwd lng="en"><![CDATA[tillage]]></kwd>
<kwd lng="en"><![CDATA[reserve root, seeding density]]></kwd>
</kwd-group>
</article-meta>
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