Francisco de Brito Melo

Uso e qualidade da água subterrânea para irrigação no semi-árido piauiense

The semi-arid region in the State of Piaui, Brazil, is characterized by low rain fall and high evapotranspiration. However, the groundwater reserves make possible the economic development by underground hydrogeology characteristics, which allow extractions of high water flow with good quality, in most of the cases. However, some wells reached formations that have low discharge and water with high salt concentration, which if used for irrigation may cause salinization and sodification. The main goal of this work was to characterize the different uses and quality of groundwater in a part of the semi-arid area of Piaui, with a view to its use for irrigation. Samples were collected in 225 wells distributed spatially in the area, in which the following variables were analyzed: electrical conductivity, Na, Ca, Mg, SAR, CO3, HCO3, Cl and SO4. Regarding water use, the domestic use prevailed (53.61%), followed by irrigation (21.17%), with the following irrigation methods: drip irrigation (14.03%); microsprinkler (3.83%); conventional sprinkler (16.11%); gun sprinkler and traveler irrigation machine (13.66%); surface irrigation (16.76%) and other handmade methods (35.52%). The maps of classes of use risk irrigation generated from groundwater quality showed the occurrence of sub-areas with the following classes: no restriction, moderate restriction and severe restriction.

Níveis de irrigação na cultura do feijão caupi

This work was carried out to evaluate the effect of irrigation depth on yield and production components of cowpea (Vigna unguiculata L. Walp) under soil and climatic conditions of the Coastal Tablelands in the State of Piaui - Brazil. The trial was conducted at the Embrapa Meio-Norte Experimental Area, in Parnaiba, in a sandy soil, during the period from August to October, 1998. Irrigation depths were applied through a sprinkler line source system. The treatments were constituted by combination of four depths of irrigation (449.1; 428.6; 317.1 and 194.4 mm) and two cowpea cultivars (BR 17 Gurgueia and BR 14 Mulato) arranged in a completely randomized block design in split-plot and five replications. Significant effects (p<0.05) of depth of irrigation and cultivar interaction with respect to number of pods per plant (NPP) and grain yield (GY) were observed. The highest NPP (25.6) and maximum GY (2,809 kg ha-1) for the BR 17 Gurgueia cultivar was obtained with the irrigation depth of 449.1 mm. The maximum NPP (15.0) and GY (2,103.4 kg ha-1) for the BR 14 Mulato cultivar were obtained with the irrigation depth of 363.5 and 389.9 mm, respectively.

Calibration of a capacitance probe in a Paleudult

ABSTRACT: The use of capacitance sensors is one of the methods used to quantitatively measuresoil water contents (θ, m 3 m -3 ). Sensors provide readings at desired depths and time intervals. Acapacitance probe (Diviner 2000) was calibrated for a Rhodic Paleudult from the Piaui State, Brazil. Sixaccess tubes were installed in a 5 × 2 m grid arrangement. Three moisture levels (saturated, moist anddry) were used in two replications. Probe readings and soil samplings to determine θ were made at 0.1m depth intervals down to a depth of 1.0 m. A power calibration equation was developed for eachdepth as well as for the entire soil profile (Root Mean Square Error = 0.014, R 2 = 0.93) for a θ range of0.068 to 0.264 m 3 m -3 . A separate calibration for each depth improves the correlation coefficient andminimizes RMSE. Site-specific calibration improves the accuracy for soil water monitoring.Key words: FDR probe, sensor, irrigation, soil water content CALIBRACAO DE UMA SONDA DE CAPACITÂNCIAEM UM ARGISSOLO

Fertilização nitrogenada, densidade de plantas e rendimento de milho cultivado no sistema plantio direto

Pesquisador Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA) Meio Norte, BR-64006220 Teresina, PI, Brazil

Water storage in a Plinthaqualf cultivated with sugarcane under straw levels

The objective of this work was to evaluate water storage in a Plinthaqualf under different straw levels during the fourth ratoon season of a sugarcane (Saccharum officinarum) crop. The study was conducted in the 2013/2014 crop season, with the cultivar SP-813250, at two soil depths (0.0–0.3 and 0.3–0.6 m), in a randomized complete block design, with five straw levels (0.0, 4.2, 9.5, 13.0, and 18.4 Mg ha-1) and four replicates. Soil moisture content was monitored with a time-domain reflectometer. The straw provided gains of up to 20 Mg ha-1 stems and kept increased water storage in the soil, in comparison with the soil without straw, in all evaluated periods. Maintenance of up to 50% (9.5 Mg ha-1) of sugarcane straw on soil surface promotes better water retention in the soil per Mg of straw added and delays the reach of critical water storage in the soil by up to 11 days, when compared with soil without straw cover.

Produtividade de cultivares de cebola no Semi-Árido piauiense

The yield of onion cultivars was evaluated in the Picos region, Brazil, from May to October 1999. The experimental design was of randomized complete blocks with 18 treatments and four replications. The cultivars Granex 33, Composto IPA-6, Belem IPA-9, Franciscana IPA-10, Vale Ouro IPA-11, Texas Grano 502, Conquista, Crioula, Serrana, Granex 429, Regia, Princesa, Mercedes, Duquesa, Linda Vista, Piraouro, Granex Ouro and Baia Periforme Precoce were evaluated. We evaluated the commercial and noncommercial bulb yield. The cultivars were grouped in three classes according to bulb yield (>40 t/ha; 39.9-34.6 t/ha; 32.4-26.9 t/ha). The average onion bulbs yield was 41,9 t/ha. The most productive cultivars (commercial bulbs) were Vale Ouro IPA-11 (43,7 t/ha), Franciscana IPA-10 (41,5 t/ha) and Mercedes (40,5 t/ha).

Características comerciais de alho em Picos, PI

Este trabalho teve por objetivo avaliar e selecionar cultivares de alho para as condicoes edafoclimaticas da microrregiao de Picos, PI. O experimento foi conduzido em blocos casualizados completos, com oito tratamentos e quatro repeticoes. As cultivares avaliadas foram Branco Mineiro, Centenario, Amarante, Chines, Cateto Roxo, Mexicano II, Cateto Roxo Local e Mossoro. As caracteristicas avaliadas foram altura de plantas aos 60 e 90 dias apos o plantio, produtividade de bulbos comerciais e incidencias de bulbos nao comerciais, bulbilhos aereos, pseudoperfilhamento, bulbos mal formados e de bulbos chochos. A cultivar Mossoro apresentou maior altura de plantas aos 60 e 90 dias apos o plantio. Quanto a produtividade de bulbos comerciais, a cultivar Mossoro foi a mais promissora (4,63 t/ha), porem, nao diferindo estatisticamente (P>0,05) das cultivares Cateto Roxo Local (3,94 t/ha) e Cateto Roxo (3,46 t/ha). A cultivar Branco Mineiro teve comportamento semelhante a cultivar Cateto Roxo Local e Cateto Roxo. As menores produtividades comerciais foram observadas para as cultivares Chines, Centenario, Amarante e Mexicano II. A cultivar Chines teve a maior percentagem de bulbos nao comerciais (80,05%). Observou-se, um baixo indice de pseudoperfilhamento para todas as cultivares avaliadas.

Zinc fertilization in cowpea cultivars

Zinc (Zn) is an essential micronutrient for plants, due to its role as a functional, structural, or regulatory cofactor in a large number of enzymes. The element is necessary for the synthesis of tryptophan, which is a precursor of indoleacetic acid. The aim of this study was to evaluate the behavior of two cowpea cultivars fertilized with four doses of Zn (0.0, 2.0, 4.0, and 6.0 kg of Zn ha-1) regarding dry grain yield (PGS), in addition to quantifying leaf and grain Zn content and grain crude protein. The experiment was conducted in the town of Brejo, in the state of Maranhao, Brazil. A 4 x 2 factorial scheme was used with four replications. Response functions were adjusted by calculating the Zn doses which provided a maximum technical efficiency for each genotype. The tested cultivars of cowpea showed no great difference regarding Zn demand applied to the soil, ranging from 3.2 to 3.4 kg of Zn ha-1 for BRS Tumucumaque and BRS Guariba, respectively. Concerning Zn use efficiency, BRS Guariba was more responsive than was BRS Tumucumaque, i.e. the same dose of Zn produced 70 kg grain and 2.1 kg crude protein per hectare.

Agronomic performance of 'BRS' Itaim cowpea beans at different planting densities under no-tillage and conventional systems

Cowpea beans play an important role in Brazilian farming, mainly in northern and northeastern regions, where it is widely grown among smallholder farmers. In recent years, commercial farmers have expanded its cultivation, mostly to the Midwest. This study aimed at evaluating the planting density of ‘BRS Itaim’ black-eyed cowpea beans under conventional (CT) and no-tillage (NT), with 75% mulch in the first year. Two experiments (CT and NT) were conducted at Embrapa Meio-Norte in Teresina - PI (Brazil), during the 2014/2015 harvest. Both experiments were carried out in a randomized block design with four replicates, considering the planting densities (PD) 12, 16, 20, 24, and 28 plants m-2. In both systems, grain yields (GY) and the number of pods per unit area (NPA) responded quadratically to an increase in PD, while a linear decreasing response was observed for the number of pods per unit area. The maximum grain yields (GY) were 1,492 kg ha-1 (23.8 plants m-2) and 1,136 kg ha-1 (23.2 plants m-2) under CT and NT, respectively. The NPA was most correlated with GY, presenting a value of 0.74 (P<0.01). The survival rate of cowpea seedlings was 94% under CT and 88% under NT. This larger reduction under NT might be attributed to a higher incidence of fungi in the soil under this system (e.g. Furasium solani, Fusarium oxysporum, Macrophomina phaseolina, Pythium spp, Sclerotium rolfsii and Rhizoctonia solani).