Foliar fertilization with zinc in pecan trees

The objective of this study was to assess the changes in leaflet zinc (Zn), leaf nutritional state, vegetative and physiological parameters, and yield quality in pecan trees sprayed with different Zn compounds. Eight-year-old ‘Western Schley’ pecan trees grafted to native seedlings were treated with ZnNO3 (100 mg·L−1 Zn), Zn-EDTA (50, 100, and 150 mg·L−1 Zn), and Zn-DTPA (100 mg·L−1 Zn) and compared with the Zn-untreated control. After 3 years of evaluation, the trees with the best appearance were those treated with ZnNO3 (100 mg·L−1 Zn) and Zn-DTPA (100 mg·L−1 Zn), which showed leaf Zn concentration increases of 73% and 69%, respectively, when compared with the controls. The chlorophyll values of the Zn-treated trees reached 46 SPAD units, equivalent to 43 mg·kg−1 dry weight (DW) of chlorophyll compared with values of 22 mg·kg−1 DW in Zn-deficient leaves. On a leaf area basis, chlorophyll value was 37% lower under Zn deficiency conditions than that of Zn-treated trees. Nut quality was unaffected by the Zn treatments. Data suggest that Zn-DTPA and Zn-NO3 are good options to carry out foliar Zn fertilization in pecan trees.Research supported by the Mexican National Council of Science and Technology (CONACYT) and the Chihuahua State Government. Project code: CHIH-2006-COI-54685.Peer reviewe

Plant and livestock waste compost compared with inorganic fertilizer: nutrient contribution to soil

The use of livestock and plant wastes, as sources of nutrients and organic material to the soil, is a viable alternative to chemical fertilizers, which eventually cause serious risks to agroecosystems. The present study was conducted in 2013 in a greenhouse at FACIATEC-UACH, Chihuahua, México. Four composts made with (a) cow manure, (b) hen manure, (c) sawdust and (d) maize stover were evaluated for their contribution of the soil macronutrients NO3-, P=, K+, Ca++, Mg++ and Na+ and compared with urea as a synthetic fertilizer and a control without fertilizer. The experiment was based on a completely randomized design; statistical analysis included an analysis of variance using the statistical package SAS (Statistical Analysis System) version 9.3.1 and comparison of means with the Tukey procedure (a = 0.05). Results suggest that five of the compost treatments increased the concentration of NO3-. Hen manure significantly outperformed cow manure in providing NO3- and P=. Likewise, the sawdust-based compost significantly affected the content of NO3-, outperforming the treatment based on maize stover. The concentration of Ca++ and Mg++ in soils resulting from the applied composts was lower than in the treatment with inorganic fertilizer, but that of Na+ was statistically higher than in the inorganic fertilizer treatment. This evidence suggests that the use of organic fertilizers, of either animal or plant origin, is a beneficial source of soil nutrients with high potential in sustainable agriculture

Zinc nutritional status of pecan trees influences physiological and nutritional indicators, the metabolism of oxidative stress, and yield and fruit quality

7 Pags.- 1 Tabl.- 4 Figs.In the United States of America and in Mexico, zinc deficiency is a common nutritional disorder in pecan trees [Carya illinoinensis (Wangenh.) C. Koch], especially in calcareous soils. This study in Chihuahua, northern Mexico, analyses the effects of zinc nutritional status on various physiological and nutritional indicators, on the metabolism of oxidative stress, and on the yield and fruit quality of pecan. The aim was to identify possible bioindicators of soil zinc deficiency. The experimental design was completely randomized with four nutritional conditions with respect to zinc: a control and three levels of zinc deficiency - slight, moderate and severe. Zinc deficiency is characterised by small leaves with interveinal necrosis and rippled leaf margins. The lowest values of leaf area, SPAD values, total N and NO3 concentration were observed under conditions of severe zinc deficiency. With worsening zinc deficiency, results indicate an increased enzymatic activity of superoxide dismutase, catalase and glutathione peroxidase. Interestingly, under severe zinc deficiency there are decreases in trunk cross-sectional area growth, in yield and in percentage kernel. Increased activity of superoxide dismutase, catalase and peroxidase enzymes is associated with detoxification of reactive oxygen species. The activity of enzymes detoxifying reactive oxygen species lessens the negative effects of zinc deficiency stress, and may be good bioindicators of zinc deficiency and its visual symptoms on pecan trees.The authors express their gratitude to Sistema Producto Nuez México and to Sistema Producto Nuez del Estado de Chihuahua, Mexico, for financial support granted for the completion of the present research.Peer reviewe