Application of Corn Straw and Woody Peat to Improve the Absorption and Utilization of 15N-Urea by Maize

Increasing nitrogen fertilizer use efficiency has become an environmental and economic demand in order to minimize losses of nitrogen and maximize the output from nitrogen added. The application of organic amendments with N fertilizers could be proposed as an important economic and environmental practice for improving N fertilizer use. A two-year field experiment was carried out using the 15N tracer technique to study the impact of corn straw and woody peat application on uptake and utilization of N fertilizer by maize plant. Three treatments were set up: CK (15N labeled urea alone), CS (15N labeled urea + crushed corn straw) and WP (15N labeled urea+ crushed woody peat). The results showed that, as compared to CK, both straw and peat treatments led to (i) an increase in yield of maize, 15N urea utilization rate, and residual 15N urea remained in soil by 11.20% and 19.47%, 18.62% and 58.99%, 41.77% and 59.45%, respectively, but (ii) a decrease in the total loss rate by 6.21% and 16.83% (p < 0.05), respectively over the two seasons. Moreover, the significantly highest effect was recorded with woody peat application rather than that with corn straw. Our study suggests that corn straw and woody peat can be used as organic fertilizers to increase maize yields, promote nitrogen fertilizer balance sheet, reduce the leaching of N fertilizer into the subsurface soil layer, and facilitate the further absorption and utilization of soil residual nitrogen. Therefore, the application of humified organic material play a crucial role in N utilization efficiency enhancement.

RUMINAL AMMONIA AND BLOOD UREA METABOLISM IN SHEEP FED HAY WITH OR WITHOUT CONCENTRATE SUPPLEMENT

Metabolism of ruminal ammonia and blood urea was investigated in West African Dwarf ewes and wethers, fed a low quality hay with or without concentrate supplementation, using single injection of [15N] ammonium chloride (HN4Cl) or [15N] urea into the rumen and blood respectively. The percentages of 15N administered intraruminal as HN4Cl recovered in the urine, faeces and milk of the ewes were 4.3, 9.0 and 3.1, Also 32.3 and 28.7% of [15Nl urea administered into the blood were recovered in the urine of the wethers. Ruminal ammonia contributed 50.6% or protozoal-N in sheep fed hay and 14.2 78.7 and 35.0% respectively in sheep fed hay and concentrate. Also, 59.0 and 7.9% of ruminal ammonia-N was derived from blood urea of sheep fed hay and hay plus concentrate respectively. The inclusion of concentrate in the diet increased the extent of ruminal bacteria protein synthesis but not that of the protozoa, However, the contributions of ruminal ammonia to blood urea synthesis and of blood urea to ruminal ammonia were Sharply decreased in the presence of the concentrate.

Review of Lysine Metabolism with a Focus on Humans

ABSTRACT Lysine cannot be synthesized by most higher organisms and, therefore, is an indispensable amino acid (IAA) that must be consumed in adequate amounts to maintain protein synthesis. Although lysine is an abundant amino acid in body proteins, lysine is limited in abundance in many important food sources (e.g. grains). Older observations assigned importance to lysine because animals fed a lysine-deficient diet did not lose weight as fast as animals placed upon other IAA-deficient diets, leading to the theory that there may be a special pool of lysine or metabolites that could be converted to lysine. The first step in the lysine catabolic pathway is the formation of saccharopine and then 2-aminoadipic acid, processes that are mitochondrial. The catabolism of 2-aminoadipic acid proceeds via decarboxylation to a series of CoA esters ending in acetyl-CoA. In mammals, the liver appears to be the primary site of lysine catabolism. In humans, the metabolic and oxidative response of lysine to diets either restricted in protein or in lysine is consistent with what has been measured for other IAAs with isotopically labeled tracers. Intestinal microflora are known to metabolize urea to ammonia and scavenge nitrogen (N) for the synthesis of amino acids. Studies feeding 15N-ammonium chloride or 15N-urea to animals and to humans, demonstrate the appearance of 15N-lysine in gut microbial lysine and in host lysine. However, the amount of 15N-lysine transferred to the host is difficult to assess directly using current methods. It is important to understand the role of the gut microflora in human lysine metabolism, especially in conditions where dietary lysine intake may be limited, but better methods need to be devised.

Nitrogen use efficiency of 15N urea applied to wheat based on fertiliser timing and use of inhibitors

Improving fertiliser nitrogen (N) use efficiency is essential to increase productivity and avoid environmental damage. Using a 15N mass balance approach, we investigated the effects of five N fertiliser management strategies to test the hypothesis that increasing uptake of applied N by wheat improves productivity and reduces loss of N in a semi-arid environment. Three experiments were conducted between 2012 and 2014. Treatments included urea application (50 kg N/ha) at sowing with and without nitrification inhibitor (3,4-dimethylpyrazole phosphate, DMPP) and surface broadcast with and without urease inhibitor (n-butyl thiophosphoric triamide, NBPT) at the end of tillering plus an unfertilised control. It was found that deferring fertiliser application until the end of tillering decreased losses of fertiliser N (35–52%) through increasing uptake by the crop and or recovery in the soil at harvest, while maintaining yield except when rainfall following application was low. In this case, deferring application reduced fertiliser uptake (− 71%) and grain yield (− 18%) and increased recovery of N in the soil (+ 121%). Use of DMPP or NBPT reduced N loss where seasonal conditions were conducive to denitrification during winter (DMPP) and volatilisation or denitrification later in the season (NBPT). Their effect on grain yield was less significant; DMPP increased yield (+ 3–31%) in all years and NBPT increased yield (+ 7–11%) in 2 of 3 years compared to unamended urea. The majority of crop N uptake was supplied from soil reserves and as a result, crop recovery of applied N was not strongly related to grain yield response.

Biochar Effects on Mineral Nitrogen Leaching, Moisture Content, and Evapotranspiration after 15N Urea Fertilization for Vegetable Crop

Globally, mineral nitrogen (N) losses as nitrate leaching (NL) are a substantial portion of applied fertilizer and cause surface and sub-surface water contamination. To precisely measure NL and its interlink parameters, biochar soil amendment was tested in this study. Three treatments—biochar (BC), without biochar (WB) with 15N urea (300 kg/ha), and control (no fertilization)—were tested in soil-filled lysimeters (circular PVC (Polyvinyl Chloride) tank of 30 cm diameter and 35 cm height) equipped with moisture content sensors and weighing assembly for the consecutive two cropping of Brassica Camprestis Var. Chinensis. The 15N-urea in the first season and the poultry manure in the second season were applied, but the fate of the 15N was examined in leachate, dry matter, and soil. As compared to WB, BC significantly decreased mineral N leaching, including nitrate levels (35%), increased electrical conductivity (68.5%), and water availability (20% inches per foot), while there was a non-significant increase in biomass per plant (2.84%), evapotranspiration (8.33%), dry matter (6.89%), and a decrease in mean leachate volume (7.63%). Moreover, BC accumulated values were higher than WB, as N uptake (38%), water use efficiency (12.24%), maximum fresh weight (11.4%), and soil N retained (185%) after cropping. The soil pH, the bulk density, and the total nitrogen were changed but presented non-significant differences. Therefore, biochar can increase soil N retention and available water to improve water use efficiency and decrease potential N leaching.

Evaluation of Cowpea (Vigna unguiculata L.walp) Genotypes for Biological Nitrogen Fixation in Maize-cowpea Crop Rotation

Nitrogen is a major plant nutrient which is most limiting in the soil due to soil losses of mineral nitrogen (N) form. To ensure availability of nitrogen in the soil, the study was conducted to screen four cowpea genotypes for Biological Nitrogen Fixation (BNF) and their contribution to maize yield in maize- cowpea rotation. The cowpea genotypes used were mutants LT11-3-3-12 (LT) and BB14-16-2-2 (BB) and their parental varieties Lutembwe (LTPRT) and Bubebe (BBPRT) respectively. Trials were established at two sites (Chisamba and Batoka) of different soil types. The Randomized Complete Block Design (RCBD) with three replications was used. Labelled 15N urea was applied at 20kgNha-1 on the four cowpea genotypes during 2015/16 growing season. Cowpea plant parts were dried and milled for 15N isotopic analysis. The data collected included Nitrogen content and atom % 15N excess in the fixing cowpea genotypes and non-nitrogen fixing pearl millet to determine total nitrogen derived from the atmosphere (TNdfa) and total nitrogen (TN) in plant parts which were further used to compute Biological Nitrogen Fixation (BNF). The results showed that BNF by cowpea genotypes at Chisamba was 63.9 kg ha-1 and was significantly (P&lt;0.001) more than BNF of 6.6 kgha-1 at Batoka. The LT mutant fixed significantly (P&lt;0.001) higher nitrogen of 86.1 kgha-1 and 16.5kg ha-1 at Chisamba and Batoka respectively than other genotypes. However, both BB and LT mutants significantly fixed more nitrogen than their parents and have demonstrated to increase maize grain yields up-to 12 tha-1 in the maize &ndash; cowpea rotation.