Assessment of linear anionic polyacrylamide application to irrigation canals for seepage control

South- central area of Chile area has a Mediterranean climate and high crop water requirements. Irrigation water is distributed through long channels which have low water conveyance efficiency (Ec), difficult to improve by conventional techniques. The objective of this study was to quantify Ec and to evaluate the use of Linear Anionic Polyacrylamide (LA-PAM) to reduce seepage losses. The study was carried out in south-central area of Chile, (UTM Coordinate N 5745000; E 725000 m, datum is WGS-84, zone 18S) in 250 km of channels whose flow varied between 0.12 and 24.6 m3 s–1. Water users indicated channel reaches with potential low Ec, which were selected for LA-PAM application. In 11 reaches between 0.51 and 3 km in length, 1 to 3 LAPAM applications were performed at rates of 10 kg ha–1, considering the wet perimeter area as basis of calculation. Thirty-one LA-PAM applications were performed over a 30.5 km length. Most of the channels were large enough to allow motorboat moving against the current to carry-out LA-PAM application. Water flow was measured (StreamPro ADCP) at both ends of selected reaches before and after granular LAPAM application. Weekly measurements were made to quantify treatment effect duration. Water turbidity and temperature were measured. Channels showed variable Ec from 87% to 94%. Two reaches showed 6% water gains. In more than 80% cases LA-PAM effect was positive, achieving loss reductions of 15 to 760 L s–1. In other cases LA-PAM had a negative effect since it mainly affected water entry into the channel. It was determined that field conditions referred by users as indicators of Ec are not always correct and vary in time according to climatic conditions. Ec was estimated and it was possible to reduce seepage through LA-PAM applications. This allow increasing irrigation security in critical periods, especially under drought conditions

Efecto de Tres Sistemas de Labranza Sobre el Nivel de Humedad en el Perfil del Suelo

Conservationist tillage systems have advantages over conventional systems because they allow the protection of natural resources. However, it is important to validate these advantages to encourage the adoption of this type of technology by farmers. The objective of this study was to determine if the type of tillage affects moisture content in the soil profile. To this end, the effect of three tillage systems on water availability in an Ultisol soil was compared. The treatments were: no tillage and burning residues (CL+Q); no tillage without burning residues (CL-Q); and traditional tillage (TRAD). The results showed that between end of tilling - beginning of internode elongation and heading, the mean value of the moisture index for CL-Q was 1.023, significantly higher than 1.001 and 0.998 corresponding to CL+Q and TRAD, while between heading and harvest the index for CL-Q was 0.963, statistically higher than 0.941 and 0.938 corresponding to CL+Q and TRAD. This effect was due to water content differences in the soil profile above 40 cm. Considering the three periods of plant development together, the mean value of the moisture index for CL-Q was 1.015, statistically higher than 0.996 and 0.990 from CL+Q and TRAD. This study confirmed that in terms of soil moisture retention in the profile of an Ultisol soil, it is recommendable to use zero tillage without burning the residues.Los sistemas de labranza conservacionista tienen ventajas sobre los convencionales, puesto que permiten proteger los recursos naturales. Sin embargo, es importante demostrar estas ventajas para fomentar la adopci\uf3n de este tipo de tecnolog\uedas por los agricultores. El objetivo de este estudio fue determinar si el tipo de labranza afecta el contenido de humedad en el perfil del suelo. Para ello se compar\uf3 el efecto de tres sistemas de labranza sobre la disponibilidad de agua en un suelo Ultisol. Los tratamientos fueron: cero labranza con quema (CL+Q); cero labranza sin quema (CL-Q); y labranza tradicional (TRAD). Los resultados mostraron que entre t\ue9rmino de macolla-inicio de enca\uf1ado y espigadura se obtuvo un \uedndice de humedad promedio de 1,023 en CL-Q, que fue significativamente mayor a 1,001 y 0,998 correspondientes a CL+Q y TRAD, mientras que entre espigadura y cosecha el \uedndice para CL-Q fue de 0,963, significativamente mayor a 0,941 y 0,938 correspondientes a CL+Q y TRAD, respectivamente. Este efecto se produjo gracias a las diferencias en los contenidos de humedad del perfil del suelo hasta los 40 cm. Al considerar los tres per\uedodos fenol\uf3gicos en conjunto el \uedndice de humedad promedio obtenido en CL-Q fue 1,015, significativamente mayor que 0,996 y 0,990 de CL+Q y TRAD. Este trabajo permiti\uf3 comprobar que desde el punto de vista de la retenci\uf3n de humedad en el perfil de un suelo Ultisol, es recomendable utilizar cero labranza sin quema de residuos

Efecto de tres sistemas de labranza sobre el nivel de humedad en el perfil del suelo.

Los sistemas de labranza conservacionista tienen ventajas sobre los convencionales, puesto que permiten proteger los recursos naturales. Sin embargo, es importante demostrar estas ventajas para fomentar la adopción de este tipo de tecnologías por los agricultores. El objetivo de este estudio fue determinar si el tipo de labranza afecta el contenido de humedad en el perfil del suelo. Para ello se comparó el efecto de tres sistemas de labranza sobre la disponibilidad de agua en un suelo Ultisol. Los tratamientos fueron: cero labranza con quema (CL+Q); cero labranza sin quema (CL-Q); y labranza tradicional (TRAD). Los resultados mostraron que entre término de macolla-inicio de encañado y espigadura se obtuvo un índice de humedad promedio de 1,023 en CL-Q, que fue significativamente mayor a 1,001 y 0,998 correspondientes a CL+Q y TRAD, mientras que entre espigadura y cosecha el índice para CL-Q fue de 0,963, significativamente mayor a 0,941 y 0,938 correspondientes a CL+Q y TRAD, respectivamente. Este efecto se produjo gracias a las diferencias en los contenidos de humedad del perfil del suelo hasta los 40 cm. Al considerar los tres períodos fenológicos en conjunto el índice de humedad promedio obtenido en CL-Q fue 1,015, significativamente mayor que 0,996 y 0,990 de CL+Q y TRAD. Este trabajo permitió comprobar que desde el punto de vista de la retención de humedad en el perfil de un suelo Ultisol, es recomendable utilizar cero labranza sin quema de residuos

Effect of three tillage systems on moisture content in the soil profile

Conservationist tillage systems have advantages over conventional systems because they allow the protection of natural resources. However, it is important to validate these advantages to encourage the adoption of this type of technology by farmers. The objective of this study was to determine if the type of tillage affects moisture content in the soil profile. To this end, the effect of three tillage systems on water availability in an Ultisol soil was compared. The treatments were: no tillage and burning residues (CL+Q); no tillage without burning residues (CL-Q); and traditional tillage (TRAD). The results showed that between end of tilling - beginning of internode elongation and heading, the mean value of the moisture index for CL-Q was 1.023, significantly higher than 1.001 and 0.998 corresponding to CL+Q and TRAD, while between heading and harvest the index for CL-Q was 0.963, statistically higher than 0.941 and 0.938 corresponding to CL+Q and TRAD. This effect was due to water content differences in the soil profile above 40 cm. Considering the three periods of plant development together, the mean value of the moisture index for CL-Q was 1.015, statistically higher than 0.996 and 0.990 from CL+Q and TRAD. This study confirmed that in terms of soil moisture retention in the profile of an Ultisol soil, it is recommendable to use zero tillage without burning the residues

Permeabilidad de acuíferos no-confinados cerca de pozos norias en el Secano Costero e Interior, Región del Libertador General Bernardo O’Higgins, Chile

In the dryland of the Libertador General Bernardo O’Higgins Region in Chile, most farmers rely on wide and shallow hand-dug wells as their primary source of water during the dry summer. Few of these wells have sufficient yield for more than domestic use (human consumption, livestock, and irrigation of a subsistence garden). To more accurately assess available groundwater resources, saturated hydraulic conductivity (K) of aquifers in the eight counties that comprise this region’s dryland was estimated using evacuation and recovery tests in 353 hand-dug wells. K followed a log-normal distribution and ranged over nearly five orders of magnitude. County median K varied by a factor of 5 and a slight increasing K trend in the southward direction. In one northern county, less than 4% of the sites had K > 4 m d-1. In the t two southernmost counties, approximately one-quarter of the K values exceeded 4 m d-1. This is approximately the minimum K required for a typical well (1 m diameter and 3 m depth below the water table) to yield 1 L s-1 of water, which is roughly the yield required to irrigate 1 ha. Aquifers located where parent material was predominantly intrusive granite had slightly higher and statistically significant K than those formed predominantly of metamorphic and sedimentary rock. A semi-variogram of K provided weak evidence of a characteristic length scale of approximately 4 km.La mayoría de los agricultores del secano de la Regióndel Libertador General Bernardo O’Higgins depende de pozos noria, constituyendo su principal fuente de agua durante el verano. Pocos pozos tienen rendimiento suficiente para un uso mayor que el doméstico (consumo humano, ganadería y riego). A fin de evaluar con mayor precisión los recursos hídricos subterráneos disponibles,mediante pruebas de bombeo-recuperación se estimó la conductividad hidráulica saturada (K) de los acuíferos en 353 pozos distribuidos en ocho comunas del área. K siguió una distribución log-normal, con una K máxima casi cinco órdenes de magnitud mayor que la mínima. La mediana de K varió en un factor de 5 por comuna y tuvo una ligera tendencia creciente en dirección Sur. En una comuna del Norte, se estimó que menos del 4% de los sitios presentaron K > 4 m d-1. En dos comunas del Sur, alrededor del 25% de los valores de K superaron los 4 m d-1, valor mínimo requerido para que un pozo de dimensiones típicas (1 m de diámetro y 3 m de profundidad bajo el nivel de agua) produzca 1 L s-1 de agua, suficiente para regar 1 ha. Los acuíferos localizados en áreas con material predominantemente granítico, tuvieron levemente mayores K, estadísticamente significativos, que los formados predominantemente de rocas metamórficas y sedimentarias. El semi-variograma de K indicó un rango de dependencia de 4 km