ABSTRACT Several factors interact controlling ammonia (NH3) volatilization contributing to the variability of results reported in the literature. In the milkmaid basin of Santa Fe there is no information on nitrogen loss through NH3 volatilization from dairy cattle slurry (DCS) applied to soil. The objective of this study was to quantify NH3 volatilization from application of different rates of dairy cattle slurry in winter and summer in a soil in the central region of Santa Fe (Argentina). A field experiment was carried out and four treatments were applied. The treatments included the application of three different doses of DCS: D1 = 60 m3 ha-1, D2 = 120 m3 ha-1, D3 = 180 m3 ha-1 and a control treatment without application (D0). The experiment was conducted in summer (February) and winter (July) in a randomized complete design with two replications. The NH3 volatilization was significantly higher in the summer than in the winter. The volatilization initial rates were not affected by the DCS rates applied in the different seasons of the year. The decrease in NH3 volatilization rates was related to the season of the year. The NH3 volatilization rates decrease faster in DCS treatments compared to control. This study demonstrated that NH3 volatilization was strongly related to the season of the year and to a lesser extent with the DCS rates applied.

RESUMEN Los factores involucrados en la volatilización de amoníaco (NH3) son diversos e interactúan entre sí, lo que genera variabilidad en los resultados reportados en la literatura. En el centro de la cuenca lechera santafesina no existe información sobre las pérdidas de nitrógeno por volatilización generadas a partir de la aplicación al suelo de efluentes líquidos de tambo (ELT). El objetivo de este estudio fue cuantificar la volatilización de NH3 luego de la aplicación de diferentes dosis de efluentes líquidos de tambo en invierno y verano en un suelo de la región centro de Santa Fe (Argentina). El experimento se realizó a campo y se aplicaron cuatro tratamientos que consistieron en la aplicación de tres dosis diferentes (D1= 60 m3 ha-1, D2 = 120 m3 ha-1, D3 = 180 m3 ha-1) de ELT y un tratamiento testigo sin aplicación (D0). El experimento fue realizado en verano (febrero) y en invierno (julio) siguiendo un diseño completamente aleatorizado con dos repeticiones. La volatilización de NH3 fue significativamente mayor en verano respecto de invierno. Las tasas iniciales de volatilización de NH3 no fueron afectadas por las dosis de ELT aplicadas en las distintas estaciones del año. La disminución de las tasas de volatilización estuvo relacionada con la estación del año y decrecieron más rápido en los tratamientos con ELT comparado con el testigo. Los resultados demuestran que la volatilización de NH3 está fuertemente relacionada con la estación del año y en menor medida con la dosis de ELT aplicada.

The objective of this research was to analyze the effect of the use of plots-nighttime and liming on soil properties in a degraded Aquic Argiudoll. In a field experiment three treatments were established: a) plots-nighttime (N), b) plots-nighttime+liming (NC) and c) control without amendments (T). The pH in NC increased compared to T and N. The CIC and P increased in N and NC respect to T. CIC increased in NC respect to N. Ca ++ increased in NC respect to T and N. No differences were detected in TOC, COP and CE. The IHO was narrower in T.

El objetivo fue analizar el efecto del lote-nochero y la aplicación de carbonato de calcio (CaCO3) sobre las propiedades edáficas de un Argiudol ácuico degradado. Se evaluaron a campo tres tratamientos: a) lote-nochero (N), b) lote-nochero+aplicación de CaCO3 (NC) y c) testigo sin enmiendas (T). El pH en NC aumentó comparado con T y N. La CIC y P se incrementaron en N y NC respecto de T. Sólo la CIC aumentó en NC respecto de N. El Ca++ se incrementó en NC respecto de T y N. No se detectaron respuestas en COT, COP y CE. El IHO fue más estrecho en T.

ABSTRACT Measurements of the soil cone index are widely used to assess soil resistance to root penetration (SR) and to monitor the soil compaction status of agricultural fields. However, soil sampling for SR estimation is a rather challenging task in view of the high spatial and temporal variability of the soil. This study proposed a bootstrapping method to determine the minimum sample size required to estimate the vertical profile of mean soil cone index (CI) values at different levels of precision and confidence. For this purpose, CI data from a Typic Argiudoll under no-tillage before and after chiseling was used. A total of 151 CI profiles were recorded before and after chiseling in a 3,200 m2 (40 × 80 m) no-tillage area at sampling points distributed on a horizontal 5 × 5 m aligned grid and from the top layer to 0.40 m depth by in 0.02 m intervals. A modified bootstrap routine was developed to estimate the sampling distribution of the sample mean and medians of CI values per layer. The minimum sample size to estimate the vertical profile of mean CI values at different levels of precision and confidence was determined from data of the whole soil profile, including the autocorrelation of CI readings in the vertical direction. Tilling increased the variability of this measurement and thus the sampling efforts to achieve the same level of precision and confidence were different before and after the procedure. The standard errors of sample medians estimated by bootstrapping were higher than those corresponding to sample means. In addition, to achieve the same level of precision and confidence, the estimation of the vertical profile of mean CI values based on sample medians required more observations than based on sample means. This study shows that the viability of the bootstrap approach to determine the implications of soil variability on the sampling efforts required for an accurate estimation of the vertical distribution of resistance in soils under different managements.

During the last decade, the soil use intensification, the high nutrient extraction rates and the excessive use of nitrogen fertilizer have increased the degradation of Santa Fe soils. The objective of this study was to quantify the differences among cultivated soils (SC) and their respective non-cultivated situations (SNC) for diverse chemical and biological attributes. The following properties were evaluated in typical and aquic Argiudolls of the center of Santa Fe:,organic matter (MO), pH, exchangeable bases (calcium, magnesium, sodium and potassium) and cation exchange capacity (CEC) in two depths (0-15 and 15-30 cm). The comparison between SNC and SC showed that, in both depths, a decrease took place of the values of MO (near 30%), calcium (20%), magnesium (30%) and pH (up to 0,6 units in the 0-15 cm layer). The exchangeable potassium and the cation exchange capacity showed significant decreases in SC compared to SNC only in the 0-15 cm layer. The actual content of K corresponds to 64% of the original value. The exchangeable sodium was the only chemical parameter that did not show a significant alteration due to the soil use. The results of this study confirm that the Argiudolls of the center of Santa Fe suffered a significant change in some of their properties in relation to their natural situation.

Durante las últimas décadas la intensificación en el uso del suelo, las elevadas tasas de extracción de nutrientes y el incremento en el uso de fertilizantes nitrogenados llevaron a marcados procesos de degradación de los suelos de la región central de Santa Fe. El objetivo de este trabajo fue cuantificar las diferencias existentes entre suelos cultivados (SC) y sus respectivas situaciones no cultivadas (SNC) para diversos atributos químicos y biológicos. En suelos Argiudoles típicos y ácuicos del centro de Santa Fe se evaluaron, en dos profundidades (0-15 y 15-30 cm), los siguientes atributos: materia orgánica (MO), pH, bases intercambiables (calcio, magnesio, sodio y potasio) y capacidad de intercambio catiónico (CIC). Comparando SNC y SC, en ambas profundidades, hubo una reducción del contenido de MO (próxima a 30%), de Ca++ (20%), de Mg++ (30%) y del pH (de hasta 0,6 unidades en los 0-15 cm). La capacidad de intercambio catiónico y los niveles de K+ disminuyeron significativamente sólo en los 0-15 cm, encontrándose actualmente el 64% del potasio original. El sodio intercambiable fue el único parámetro químico que no sufrió alteración significativa debido al uso de los suelos. Los resultados de este estudio confirmarían que los suelos Argiudoles del centro de Santa Fe sufrieron una alteración significativa de la mayoría de sus propiedades en relación a su situación prístina.

A compactação do solo causa severos problemas devido a que gera diferentes mudanças nas características das plantas. Não existem métodos que possibilitem o uso das mudanças da morfologia das raízes como indicadores de níveis de compactação do solo. Avaliaram-se se alterações morfológicas nos ápices de soja podem ser utilizadas como indicadores de graus de compactação do solo. Solo peneirado a 2 mm, classificado como Typic Argiudol (série Esperanza), foi compactado até atingir os seguintes valores de densidade do solo: 1.1, 1.3 e 1.5 g cm³, para os quais corresponderam os valores de resistência mecânica de < 0.1, 0.5 e 3.5 MPa, respectivamente. A distância desde o ápice até a primeira raiz terciária e o diâmetro a 1.5 cm desde o ápice foram medidos nas raízes secundarias. Um fator de forma foi calculado fazendo o quociente entre as duas variáveis medidas. Houve uma relação inversa entre o cumprimento da raiz secundaria e fator de forma com a resistência mecânica, e uma relação direta entre esta ultima e o diâmetro das raízes secundárias. Alterações nas células da rizoderme foram determinadas. As seguintes características morfológicas se mostraram muito sensíveis a compactação do solo: i) o fator de forma, ii) as células papilosas da rizoderme, iii) malformações apicais nos pelos das raízes, e iv) diâmetro das raízes em áreas de expansão. As características morfológicas dos ápices das raízes podem ser consideradas indicadores de compactação dos solos.

Plant soil compaction poses a serious problem to agriculture because it produces different types of changes in plant characteristics. No method has been implemented to date to use root morphological changes as indicators of soil compaction levels. Therefore, the aim of the present study was to evaluate whether or not the morphological changes in root apexes of soybean (Glycine max (L.) Merrill) can be used as indicators of soil compaction levels. To this end, a silt-loamy soil material (from a Typic Argiudoll, Esperanza series), sieved through a 2 mm mesh was used and the following soil bulk density levels were determined: 1.1, 1.3 and 1.5 g cm³ for which the corresponding mechanical resistances were < 0.1, 0.5 and 3.5 MPa, respectively. The distance from the apex to the first tertiary root and the root diameter at 1.5 cm from the apex were measured on the secondary root apexes. A form factor equal to the quotient between these two variables was subsequently calculated. An inverse relationship between soil mechanical impedance and secondary root length and form factor as well as a direct relationship with the secondary root diameter were observed. Changes in rhizodermis cells were also recorded. The following morphological characteristics were found to evidence the highest sensitivity to soil compaction: i) the form factor, ii) rhizodermis papillose cells, iii) apical malformations in root hairs, and iv) root diameter in expansion areas. Taken together, the morphological characteristics of root apexes could be considered to be indicative of soil compaction.

A qualidade física do solo é fundamental para a sustentabilidade dos sistemas agropecuários e deve ser feita por meio de parâmetros que descrevem o comportamento físico do mesmo. O índice S é um desses novos parâmetros, proposto para quantificar a qualidade física do solo. Valores de S > 0,035 têm sido associados com uma boa qualidade física relacionada à produção agrícola nos solos desenvolvidos em clima temperado. Contudo, S não tem sido avaliado em solos tropicais. Consequentemente, a hipótese deste trabalho é que S pode ser utilizado como indicador da qualidade física de um Latossolo Vermelho distroférrico cultivado com milho em sistemas de plantio direto (PD) e de preparo convencional do solo (PC). Amostras indeformadas de solo foram obtidas em PD e PC nas posições linha e entrelinha da cultura de milho. A densidade do solo foi medida e o índice S foi calculado usando uma função de pedotransferência obtida no mesmo, em condições experimentais. O índice S diferenciou os sistemas de preparo e posições de amostragem, sendo S PD < S PC independente das posições de amostragem linha e entrelinha. Na posição linha verificou-se maiores valores de S tanto em PD como em PC. O valor de S diminuiu com o aumento da densidade do solo, indicando a redução da sua qualidade física, associada à compactação do mesmo. Os resultados confirmam a hipótese estabelecida e sugerem que mais estudos devem ser conduzidos para quantificar o índice S em diferentes solos e sistemas de manejo sob condições tropicais.

Soil physical quality is fundamental for the sustainability of agro ecosystems. Soil physical quality assessment must be developed using parameters that describe physical behavior. S, a new soil physical parameter has recently been introduced for assessing the soil physical quality. A good soil physical quality has been associated with values of S > 0.035 in soils from temperate climates. However, S has not been evaluated in tropical soils yet. Therefore we tested the hypothesis that S is a reliable soil physical quality indicator of a Typic Hapludox cropped with maize under no-tillage (NT) and conventional tillage (CT). Undisturbed samples were collected from each tillage system in the row and interrow positions. Soil bulk density was determined in the samples and the S parameter was calculated using a pedotransfer function from the same samples. The parameter S was able to differentiate tillage and position with S NT < S CT independent of the row and interrow sampling positions. Higher S values were verified in row position than in the interrow in both tillage systems. With the use of a pedotransfer function it was also possible to establish a negative relationship between S and soil compaction. The results confirmed our hypothesis and suggest that further studies should be carried out to evaluate S in other tropical soils and management systems.