Julie G. Lauren

A COMPARISON OF THE EFFECTS OF MICRONUTRIENT SEED PRIMING AND SOIL FERTILIZATION ON THE MINERAL NUTRITION OF CHICKPEA ( Cicer arietinum ), LENTIL ( Lens culinaris ), RICE ( Oryza sativa ) AND WHEAT ( Triticum aestivum ) IN NEPAL

SUMMARY Soil deficiencies of zinc (Zn) and boron (B) limit crop production in Nepal. Improving the micronutrient status of plants would increase yield and increase micronutrient content of the seeds, leading to better nutrition of the progeny crop and to improved human micronutrient nutrition. The primary micronutrient problem in grain legumes is B deficiency, while in rice (Oryza sativa), Zn deficiency is more important, and wheat (Triticum aestivum) suffers from both deficiencies. A series of field experiments was carried out over two seasons to compare soil fertilization and micronutrient seed priming as methods of improving Zn and B nutrition of each crop. Micronutrient treatments were evaluated for their effect on grain yield and grain micronutrient content. Soil B fertilization increased B content of the grain of lentil (Lens culinaris), chickpea (Cicer arietinum), and wheat by a factor of two to five, while increasing the yield of chickpea only. Soil fertilization with Zn had no effect on yield of any crop, but resulted in a small increase in Zn in wheat grain. Sowing micronutrient-primed seeds had no effect on yield or micronutrient content of the progeny seeds in most cases. During the first season, the primed chickpea seeds failed to emerge at either site, causing complete yield loss, but this negative effect was not observed in the second season with similar priming treatments at nearby sites, and no effect of priming on yield was observed with any other crop in either season.

Scaling properties of saturated hydraulic conductivity in soil

Abstract Variability of saturated hydraulic conductivity, k sat , increases when sample size decreases implying that saturated water flow might be a scaling process. The moments of scaling distributions observed at different resolutions can be related by a power-law function, with the exponent being a single value (simple scaling) or a function (mutiscaling). Our objective was to investigate scaling characteristics of k sat using the method of the moments applied to measurements obtained with different sample sizes. We analyzed three data sets of k sat measured in: (1) cores with small diameter and increasing length spanning a single soil horizon, (2) columns with increasing cross sectional area and constant length, and (3) columns with increasing cross sectional area and length, the longest column spanning three soil horizons. Visible porosity (macroporosity) was traced on acetate transparency sheets prior to measurement of k sat in situation (2). Six moments were calculated assuming that observations followed normal ( k sat , macroporosity) and/or log-normal ( k sat ) distributions. Scaling of k sat was observed in all three data sets. Simple scaling was only found when flux occurred in small cross sectional areas of a simple soil horizon (data set (1)). Multiscaling of k sat distributions was found when larger soil volumes were involved in the flux process (data sets (2) and (3)). Moments of macroporosity distributions showed multiscaling characteristics, with exponents similar to those from ln k sat distributions. The scaling characteristics of k sat reported in this paper agree with similar results found at larger scales using semivariograms. Scaling exponents from the semivariogram and the moment techniques could be complemented, as demonstrated by the agreement between macroporosity scaling exponents found with both techniques.

Methane emissions associated with a green manure amendment to flooded rice in California

The goals of sustainable food production and mitigation of greenhouse gas emissions may be in conflict when green manures are used in flooded rice systems. A field study was initiated in early spring 1992 near Sacramento, California to quantify the potential for enhanced methane emissions following a green manure amendment to rice. Replicate flux measurements were made twice a day every 3–4 days throughout the growing season in four treatment plots: burned rice straw, spring incorporated rice straw, burned straw plus purple vetch and spring incorporated straw plus vetch. Seasonal methane emissions ranged from 66–136 g CH4 m−2 and were 1.5 to 1.8 times higher from the straw plus vetch treatments relative to the straw only treatments. No significant differences in emissions were found between the two straw only treatments or the straw plus vetch treatments. Methane fluxes were exponentially related to soil temperature, but no effect of redox potential or floodwater depth were observed. The potential impact of these results on the global methane budget is discussed.

Effect of water management, arsenic and phosphorus levels on rice in a high-arsenic soil-water system: II. Arsenic uptake.

Rice consumption is one of the major pathways for As intake in populations that depend on a rice diet in several countries of South and South-east Asia. Pot experiments were undertaken to investigate the effects of water management (WM), arsenic (As) contaminated soil-water and Phosphorus (P) rates on As uptake in rice plants. There were 18 treatments comprising of three each of As rates (0, 20 and 40 mg kg(-1) soil) and P rates (0, 12.5 and 25 mg kg(-1) soil) and two WM (aerobic and anaerobic) strategies on winter (boro var. BRRI dhan 29) and monsoon (aman var. BRRI dhan 32) rice at the Wheat Research Center (WRC), Nashipur, Dinajpur, Bangladesh. Arsenic concentrations in rice grain and straw increased significantly (P ≤ 0.01) with the increasing As rates in the soil. Arsenic availability in soil pore-water solution was less (58%) under aerobic WM (redox potential-Eh=+135 to +138 mV; pH-6.50 at 24.3 °C) as compared to anaerobic WM (flooded: Eh=-41 to -76 mV; pH-6.43 at 23 °C). The highest total grain As content 2.23 ± 0.12 mg kg(-1) and 0.623 ± 0.006 mg kg(-1) was found in T(6) (P(12.5)As(40)-anaerobic) and T(9) (P(25)As(40)-anaerobic) in BRRI dhan 29 and BRRI dhan 32, respectively, which was significantly higher (41-45%) than in the same As and P treatments for pots under aerobic WM. The As content in rice straw (up to 24.7 ± 0.49 ppm in BRRI dhan 29, 17.3 ± 0.49 mg kg(-1) in BRRI dhan 32 with the highest As level) suggested that As can more easily be translocated to the shoots under anaerobic conditions than aerobic condition. BRRI dhan 29 was more sensitive to As than BRRI dhan 32. Under aerobic WM, P soil amendments reduced As uptake by rice plants. The study demonstrated that aerobic water management along with optimum P amendment and selection of arsenic inefficient rice varieties are appropriate options that can be applied to minimize As accumulation in rice which can reduce effects on human and cattle health risk as well as soil contamination.

Immobilization of zinc fertilizer in flooded soils monitored by adapted DTPA soil test.

Zinc (Zn) deficiency is a persistent problem in flooded rice (Oryza sativa L.). Severe Zn deficiency causes loss of grain yield, and rice grains with low Zn content contribute to human nutritional Zn deficiencies. The objectives of this study were to evaluate the diethylenetriaminepentaacetic acid (DTPA) extraction method for use with reduced soils and to assess differences in plant availability of native and fertilizer Zn from oxidized and reduced soils. The DTPA‐extractable Zn decreased by 60% through time after flooding when the extraction was done on field‐moist soil but remained at original levels when air‐dried prior to extraction. In a pot experiment with one calcareous and one noncalcareous soil, moist‐soil DTPA‐extractable Zn and plant Zn uptake both decreased after flooding compared with the oxidized soil treatment for both soils. In the flooded treatment of the calcareous soil, both plant and soil Zn concentrations were equal to or less than critical deficiency levels even after fertilization with 50 kg Zn ha−1. We concluded that Zn availability measurements for rice at low redox potentials should be made on reduced soil rather than air‐dry soil and that applied Zn fertilizer may become unavailable to plants after flooding.

Making a greener revolution: a nutrient delivery system for food production to address malnutrition through crop science.

Abstract During the 1970s, the Green Revolution basically used dwarfing genes in wheat and rice that allowed greater water and fertilizer efficiency which dramatically increased the cereal productivity and thus, increased human caloric intake of the developing world. However, having met caloric intake, there is a need to address the issues of malnutrition through a holistic food production system. For example Ca-deficient induced rickets was found in 9% of children in SE Bangladesh, illustrating the failure of that food production system to address this vital nutrient, calcium. A clinical trial has shown a minimum of increase in calcium intake of 250 mg Ca per child per day was enough to prevent rickets. In Bangladesh, a consortium of universities and other medical institutions and the International Center for Wheat and Maize Improvement (CIMMYT) has developed strategies to infuse calcium within the food delivery system. For treatment of ricketic children, a strategy was developed to use live and video drama to create community awareness of the production and/or consumption of highcalicum crops/food and calcium supplement added to the cooking rice (in this case, highly edible CaCO3 readily available throughout the country). Though this represents a very specific case study, this is a useful example of how collaboration based around crop science can address the ‘hidden’ hunger of malnutrition throughout the world.