Addition Of Plant Material Research Articles

Effects of Prey Scarcity and Plant Material as a Dietary Supplement on an Insect Predator

This study examined the effects of prey availability and the addition of plant material to the diet of a generalist insect predator (the stinkbug Podisus maculiventris). In the first experiment, third through fourth instar stinkbugs were fed a diet of mealworms (Tenebrio molitor), either one mealworm every day or one mealworm every five days. In addition, the stinkbugs had either no plant material, a green bean leaf or a slice of green bean pod. Final dry weight, developmental rate and relative growth rate were negatively affected by prey scarcity. In contrast, none of these variables were affected by the addition of plant material. In the second experiment, third instar stinkbugs through the adult stage were fed a diet of mealworms, with one every day, one every four days, or one every eight days. In addition, tomato leaves, celery leaves, basil leaves, or no plant material were provided. Fresh weight of newly ecdysed adults, developmental rate and relative growth rate of the nymphs were negatively affected by prey scarcity and plant supplement. Increasing prey scarcity reduced the total number of eggs produced by females, and egg developmental time was decreased. With addition of plant material, females laid more eggs, but weight of first instar progeny was lower. The use of plant material and the trade-off between increased egg production and reduced progeny weight may help to explain how populations of this predator survive during periods of low prey density.

Soil pH changes during legume growth and application of plant material

During cultivation of legumes soil is acidified due to proton release from roots. As a consequence of proton release, plants accumulate organic anions which may, if returned and decomposed in the soil, neutralize the soil acids. Until now the detailed processes responsible for the change in soil pH after incorporation of plant material have not been completely understood. Using a pot experiment we studied the changes in acid and base in soil during growth of field beans (Vicia faba L. cv. Alfred) and after incorporation of the plant material into the soil. Soil pH was significantly decreased by field beans from 6.00 to 5.64 in a cultivation period of 45 days. Proton release amounted to 32.7 mmol H+ pot-1, which was approximately equivalent to the accumulated alkalinity in the plant shoots (34.4 mmol). Return of field bean shoots caused a significant soil pH increase from 5.64 to 6.29. Within 7 days more than 90% of the added alkalinity was released. After 307 days incubation, soil pH decreased to 5.86 due to nitrification. In a second experiment, maize leaves (Zea mays L.), containing various concentrations of nitrogen and at various alkalinities, were incorporated into the soil. Soil pH change was positively correlated to alkalinity and malate concentration and negatively correlated to total nitrogen and water-soluble organic nitrogen of incorporated leaves. It is concluded that the soil acidification caused by legume cultivation can be partly compensated for if crop residues are returned to the soil. Addition of plant material may initially cause an increase in soil pH due to decomposition of organic anions and organic nitrogen. Soil pH may decrease if nitrification is involved. The concentrations of nitrogen and alkalinity of added plant material are decisive factors controlling soil pH change after incorporation of plant material.

Modelling of soil carbon forms after organic amendment under controlled conditions

Two different soils were amended with 14C-labelled plant material and incubated under controlled laboratory conditions for 2 yr. The dynamics of labelled and total (labelled + unlabelled) C remaining in the soil, in the microbial biomass and in the plant residue, were monitored throughout the experiment. In order to fit these results simultaneously, a model was defined including five compartments with functioning concepts according to earlier proposals and with a relatively simplified mathematical presentation among those used to describe the soil C cycle. The simultaneous fitting of microbial, plant and total labelled C appears satisfactory in the two soils, with a plausible simulation of the humification process. This model, focusing on the labelled C (added form), has allowed to fit the evolution of soil total C (labelled + unlabelled). The two fittings reveal the presence of a stable form of carbon with a half-life longer than that stabilized since the addition of plant material, but shorter than the ‘chemically stabilized organic matter’ named by Jenkinson and Rayner ( Soil Science 123, 298–303, 1977). Mineralization and humification kinetics were different in the two types of soils. These differences are expressed by model parameters and discussed with the presentation of results. In this way, hypothesis were derived in agreement with the soil mineral status and the soil carbon forms. Nevertheless, complementary investigations are necessary to verify these hypotheses and perhaps take into account newly endogenous variable in kinetic equations.

Evaluation of the Nitrogen Fertilizer Value of Plant Materials to Spring Wheat Production

AbstractUse of green manure crops has become a preferred alternative source of N. The objectives of this 3‐yr field study were to evaluate the N supplying power of 1, 2, and 3 Mg ha−1 of Austrian winter pea (Pisum sativum ssp. arvense (L.) Poir), alfalfa (Medicago sativa L.), and wheat (Triticum aestivum L.) residue. Residues were incorporated in September and the N contribution of each amendment to a subsequent spring wheat crop was calculated. We measured inorganic soil N levels and wheat yields in northern Idaho on Latahco silt loam (fine‐silty, mixed, mesic Pachic Ultic Haploxeroll) soils. Soil samples were taken during July of each year to determine residual inorganic N. Plant material addition and incorporation affected spring wheat yield and soil inorganic N level in each study. Pea and alfalfa material applied at 3 Mg ha−1 resulted in the highest spring wheat yields. Austrian winter pea residue at 3 Mg ha−1 provided a N credit of 51 to 63 kg ha−1 to spring wheat, compared to 1 to 36 kg ha−1 for alfalfa applied at the same rate. Based on inorganic soil N in July, application of 3 Mg ha−1 of Austrian winter pea, alfalfa, and wheat residue provided an N credit of 16 to 24, 21 to 26, and –1 to –25 kg ha−1, respectively. Average total N credits (soil + plant uptake) for the 3 Mg ha−1 application of Austrian winter pea, alfalfa, and wheat materials were 76, 47, and –35 kg ha−1, respectively. Estimated N recovery of Austrian winter pea material after 10 mo of incorporation was 77% (58% in wheat and 19% in soil).

Microbial biomass responses to soil drying and rewetting: The fate of fast- and slow-growing microorganisms in soils from different climates

Two soils from a temperate humid climatic region and one soil from a tropical subhumid area were incubated with 14C-labelled plant material for 27 days. Samples from each soil were then subjected to (1) drying at 40°C for 3 days, remoistening and incubation at 25°C for 10 days, or (2) storage at 4°C for 3 days and incubation. One of the soils (a silty loam from a temperate climate area) was also treated after 7 days of incubation with 14C-labelled plant material. During drying or storage and subsequent incubation of soils, biomass 12C and 14C were determined using a fumigation-extraction method. The amounts of 12CO 2 and 14CO 2 evolved and inorganic N released during 10 days' incubation were monitored. When the silty-loam soil was dried after 7 days of incubation with added plant material, biomass 14C decreased by 63% when compared to stored control soils. A smaller relative decline in biomass 14C (viz. 40%) was observed when this soil was subjected to drying 27 days after addition of plant material, suggesting that actively-growing microorganisms are more susceptible to desiccation than populations with slower growth rates. Relative decreases of biomass 12C by drying were similar for the three soils of various texture classes and carbon contents, and ranged from 14 to 30%. It was concluded that desiccation resistance was mainly determined by intrinsic properties of soil biota, presumably cell wall characteristics. For both soils from temperate climatic regions, biomass 14C declined relatively more after soil drying than biomass 12C. In contrast, similar relative decreases in biomass 14C and biomass 12C caused by drying were observed for the tropical soil. Adaptation of the microbial communities to frequent and severe desiccation of the latter soil in its natural environment, was suggested to explain those observations. Drying and rewetting of soils enhanced carbon and nitrogen mineralization during subsequent moist incubation. It was inferred that the sources of mineralization flushes were partly biomass killed by drying, and partly non-living (labelled and unlabelled) organic residues. The sizes of flushes appeared to be influenced by soil properties such as carbon content and texture.

Nature and properties of soil humic acid as influenced by incorporation of different plant materials

Properties of soil humic acids (HAs) due to incorporation of plant materials (berseem and wheat) were studied in black, laterite and red soil representing the soil orders vertisol, ultisol and alfisol, respectively. Incorporation of plant material was found to reduce the carbon content, but to increase the nitrogen content of soil HAs, irrespective of soil type. The total-N/available-N ratio of soil was found to be a determining factor for the variation in nitrogen content of soil HAs due to incorporation of plant materials. Cation exchange capacity (CEC) and optical density of soil HAs decreased, whereas coagulation threshold, absorption in different infrared regions, buffering beyond pH 7.0, and reduced viscosity increased due to addition of plant material. The amount of proton released and the drop in the initial pH of soil HAs after addition of different metal ions indicated formation of mono-, dihydroxy-metal-HA complexes which were unstable at pH 8.0 and above.

Effects of sugarcane trash and pineapple residue on titration curves, redox potential and extractable Mn and Fe in an oxisol

Undecomposed sugarcane trash and pineapple residue were dried, finely-ground and incorporated in an Oxisol at the rates of 0, 5 and 10% by weight. Effects of organic matter on the nature of titration curves, redox potential (Eh) and extractable Fe and Mn were determined. The addition of plant material of higher pH than that of soil increased the pH and buffering capacity of the soil. Soil Eh decreased with an increase in pH and rate of organic matter. The concentration of water-soluble and exchangeable Mn increased with increasing amounts of organic matter, and a decrease in soil pH was accompanied by a significant increase in water-soluble Mn. The changes in extractable Fe did not follow any definite trend.

INFLUENCE OF PLANT PARTS DECOMPOSITION ON THE DECOMPOSITION OF SOIL ORGANIC MATTER

The addition of fresh plant material to soil has been reported to accelerate the decom- position of indigenous organic matter. In some studies this claim has been disproved. This was tested using C labelled tissues of leaves, stems and roots of maize plants of different maturity stages in a laboratory study on a clay loam soil containing 0.49 percent. organic carbon. Plant materials added to the soils accelerate the decomposition of indi- genous organic matter; plant. leaves and stems decomposa more rapidly than the roots: increased loss of soll organic matter was obtained in the case of only 14-day old plant materials. Similar trends were observed in case of experiments conducted with moisture for 14 days. Considerably less soil organic matter decomposition was found in a compa- rable time after the addition of the plant materials in the preincubation experiments than in the non-preincubation experiments.

The release of phosphorus from plant material added to soil

An experiment was conducted to study the release of 32P from white clover plant residues in the presence and absence of growing oats plants in both low and high phosphorus status soils. Net reutilization of phosphorus from the added plant material after 48 days was highest in the high phosphorus system in the presence of plants (29.3 %) and least in the low phosphorus system in the absence of plants (0.6%). Watering to field capacity daily, every 3 days, or every 6 days, had no significant effect on reutilization rates. Evidence from the soil inorganic phosphorus data suggests that the addition of plant material resulted in a significant immobilization of soil phosphorus only in the low phosphorus soil in the absence of plants. The significance of these findings is discussed in relation to the large number of incubation studies conducted to study phosphorus turnover rates in soil.

The rôle of organic matter in soil fertility

Soil organic matter is a very heterogeneous mixture of substances, ranging from plant and root fragments, through the living bodies of the soil organisms, to brown amorphous humic substances produced by their activity. These materials have very different rates of decomposition in the soil and very different effects on the soil tilth and nutrient status. The method of soil cultivation used affects the stabilizing power of a limited addition of plant material. The soil organic carbon content under a well fertilized arable rotation stabilizes at about 1 % on many loam and clay soils. Incorporating a 1 year ley in the rotation or ploughing in all the straw produced may increase this by just under 0.1 %, and using normal farm dressings of farmyard manure by just over 0.1 %. These increases may be additive, but the increases are considerably smaller than this on some soils. Incorporating a 3 year grass ley in a 5 or 6 course rotation increases the carbon by between 0.15 and 0.3%, and there is some evidence that farmyard manure has a greater effect if used in a ley-arable than an all-arable rotation. A 3 year lucerne ley behaves more like a 1 year grass-clover ley except just after it has been ploughed out, though it increases the nitrifiable nitrogen in the soil for several years.

Carbohydrases in Soil as Affected by Successional Stages of Revegetation

AbstractAddition of plant materials from the first successional stage of old‐field succession caused a continuous increase in the microbial population and in activities of amylase, invertase, and cellulase for 45 days, the duration of the experiment. On the other hand, addition of plant materials from an intermediate successional stage or the climax stage resulted in an initial increase in the microbial population and in the activities of the three carbohydrases with a leveling off or decrease after 30 days. Type of organic matter added appeared to be responsible for the higher activities of the carbohydrases during the early stages of old‐field succession.