Amount Of Mulch Research Articles

Biological control of the cassava mealybug, Phenacoccus manihoti (Hom., Pseudococcidae) by Epidinocarsis lopezi (Hym., Encyrtidae) in West Africa, as influenced by climate and soil

Population data concerning the cassava mealybug (CM) Phenacoccus manihoti Matile-Ferrero, the introduced parasitoid Epidinocarsis lopezi (De Santis), and indigenous antagonists were collected, together with ecological and plant growth variables, during a survey of 414 fields covering all ecological zones of Nigeria and Benin, for evaluation in multiple regression analyses. The choice of fields was unbiased, and insect populations were estimated from large random samples. Seven years after the first release of E. lopezi, the entire area, with the exception of an isolated CM population near Lake Chad, had been colonized by the parasitoid. Within the area of distribution of E. lopezi, average CM populations were very low (1.6 CM per shoot tip), highest densities being found in the forest transition zone. The mean tip damage score on a scale from 1 to 5 was only 1.2. Only 3.2% of all tips were strongly stunted, the same percentage had more than 10 CM, and no tip had over 1000 CM. However, significant tip damage persisted on the 4.8% of fileds with unmulched, sandy soils in the forest zone. In these fields, 3.3 times fewer CM were needed to cause heavy stunting than on less stressed plants on soils with mulch, or clay, or less rain. This deleterious effect of leaching and lack of crop rotation was alleviated completely in the fields which had a small amount of mulch. Thus, agronomic factors, mediated through the condition of the plant, influenced biological control.

Effect of mulch rates and tillage systems on infiltrability and other soil physical properties of an Oxisol in Paraná, Brazil

A 7-year-old tillage trial, comprising conventional tillage (CT), minimum tillage (MT) and no-tillage (NT), was chosen to study the relative importance of controlled mulch rates and soil physical properties such as bulk density, pore volume and hydraulic conductivity upon infiltrability. Infiltration measurements were carried out with a portable rainfall simulator. Mulch consisted of soya bean residues. Soil physical analysis showed higher bulk densities in the top 20 cm under NT, whereas CT, and to a lesser extent MT, led to the development of a plough pan in 20–30 cm depth. At the same time, compaction brought about a decrease in macropores and an increase in micropores. Total porosity ranged between 56.6% and 66.4%. Hydraulic conductivity did not differ significantly between tillage systems, and overall conductivity values were very high. The main factor influencing infiltrability was the formation of a surface seal depending on the degree of soil cover by mulch, irrespective of tillage system. For all 3 tillage systems, a 100% soil cover led to the complete infiltration of a 60-mm rainfall, whereas only 20% of the applied rain infiltrated when the soil was bare and the surface completely sealed. Plant residues of 4–6 t ha −1 are proposed, as the minimum amount of mulch needed to reduce runoff and erosion effectively.

Effects of the amount of stubble mulch and overland flow on erosion of a cracking clay soil under simulated rain

A field study by using simulated rain and run-on water was carried out to determine the effects of different amounts of wheat stubble mulch (ranging from 0.1 to 3 t ha-1) and increasing discharge on erosion. Rain-flow erosion decreased with increasing amounts of stubble. Concentrations of bed-load sediment carried by rain-flow decreased with increasing plot discharge. As discharges increased, overland flow probably became too deep for drop impact to effectively disturb the soil surface and entrain sediment. Only plots carrying 0.1 t ha-1 stubble showed definite scour by overland flow. However, sediment concentrations produced by scour were well below those measured in rill flow on bare soil at this site, showing that even very small rates of stubble mulch can, in some situations, significantly reduce erosion. Discharges at which rilling develops fully must be much larger than those at which scour by overland flow is initiated. Future work will need to consider discharges much larger than those used in this study.

Infiltration rate, measured with double-ring infiltrometers and a rainfall simulator, as affected by the amount of mulch and the tillage system

Infiltration rate, measured with double-ring infiltrometers and a rainfall simulator, as affected by the amount of mulch and the tillage system

Soil Reception and Activity of Acetochlor, Alachlor, and Metolachlor as Affected by Wheat (Triticum aestivum) Straw and Irrigation

Acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide], alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] were applied in 280 L of water/ha to plots covered with 0 to 6720 kg/ha of wheat (Triticum aestivumL.) straw. At straw levels of 1120 kg/ha or greater, 50% or less of the applied herbicides were received by the soil surface before irrigation. Sprinkle irrigation (1.3 cm) washed 15 to 20% of the originally applied herbicide into the soil regardless of straw level. More metolachlor was retained on the straw than acetochlor or alachlor. Analysis of the wheat straw indicated that little water-extractable herbicide remained for all herbicides. Initial herbicidal activity on grain sorghum [Sorghum bicolor(L.) Moench.] was reduced by the presence of wheat straw at the time of application, with acetochlor being least affected and alachlor most affected. Ten days after treatment, less than 10% of the original alachlor and acetochlor remained in the soil. When planted at this time, grain sorghum response was inversely related to the amount of straw mulch that was originally present. Metolachlor residues in the soil on day 10 were 11 to 26% of that on day 0 and there was comparably less reduction in activity on grain sorghum.

Stubble Height, Basal Cover, and Herbage Production Relationships in Grasslands of Northern Greece

Leaving an amount of mulch at the end of the grazing period, before the new growing season starts is vital in maintaining productivity in grasslands on a sustained yield basis. Mulch was expressed as stubble height at 6 levels (0 3 6 9 12, and 15 cm) and 9 , , 9 was related to basal cover and herbage production attained at the end of the growing season for 5 consecutive years. The research was conducted on 3 perennial grassland sites with a Mediterraneantype climate, representing the low, middle, and high (subalpine) ecological zones in northern Greece. Bare soil was significantly increased with nearly all stubble heights as compared to the control while mulch cover had an opposite response. There were significant changes in the absolute cover of the dominant species, especially perennial bunchgrasses, but the overall grass and forb cover was not significantly affected. Stubble heights of 12 or 15 cm at the low site and 6 to 15 cm at the other two sites produced the highest yields. These were not significantly different from the control, indicating that the middle and the high sites can withstand closer grazing than the low site.

Factors Involved in the Decline of Annual Ryegrass Seeded on Burned Brushlands in California

Highlight : The effect of amount of mulch, nitrogen fertilizer, <nd clipping frequency was studied on herbage and seed production of annual ryegrass /Lolium multiflorum Lam.) seeded on a burned brushland in California. The experiment was continued for 2 years but, in the second year, actual grazing by meadow mice {Microtus californicus) was substituted for the clipping treatment. Available nitrogen in the soil was found deficient in both years but the deficiency was more pronounced in the relatively dry year. Meadow mice reduced herbage and seed yields significantly in the second year. It is concluded that the decline of annual ryegrass in burned brushlands is associated with a corresponding decline through immobilization of available soil nitrogen released by brush burning.

Chemical Fallow in a Winter Wheat-Fallow Rotation

Five fallow treatments in an alternate winter wheat (Triticum aestivumL.) fallow rotation experiment were compared over a 6-yr period at North Platte, Nebraska. During the 14-month fallow period from winter wheat harvest until winter wheat planting, plots receiving no tillage (weeds were controlled by herbicides) had the least weed growth, most soil water stored, and highest amount of surface mulch maintained. Also, the plots receiving only herbicides had the highest grain yields of all treatments. However, an average of 3.8 herbicide applications were needed to control grass weeds missed by 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) during the last 5.5 months of the fallow period. Greatest weed growth during the fallow period was on plots that received only tillage and occurred during the first 3 months after harvest.

ULAŞ DEVLET ÜRETME ÇİFTLİĞi ARAZİSİNİN RÜZGAR EROZYONU YÖNÜNDEN PLANLANMASI

ULAŞ DEVLET ÜRETME ÇİFTLİĞi ARAZİSİNİN RÜZGAR EROZYONU YÖNÜNDEN PLANLANMASI

Establishment of green panic as influenced by type, amount, and placement of vegetative mulch

Establishment of green panic (Panicum maximum var, trichoglume cv. Petrie), was measured after sowing beneath mulches of sawdust, native pasture hay, barley straw, Dolichos lablab stubble and sorghum stubble. Long, chaffed, or milled materials, all applied at 2500, 5000, or 10,000 kg ha-1 were tested. Comparisons were made with a control (no mulch) in two experiments on a self-mulching clay at Gayndah, south-eastern Queensland. Seedling emergence with all surface mulches was superior to the control and to emergence from sowing into mulch incorporated in the surface soil. Optimum rates of mulch for emergence approached 5000 kg ha-1 but varied between experiments and with mulch types. Reducing mulch particle size did not consistently improve emergence relative to long straw. In a third experiment, seedling emergence at 42 days after irrigation was directly related to the proportion of area covered by mulch irrespective of the arrangement of mulch bands. Seedling yield followed trends in plant density. Practical implications of the results are discussed.

Effects of Grazing Intensity and Cover on the Water-Intake Rate of Fescue Grassland

The Eastern Slope of the Rocky Mountains and the adjacent foothills comprise the watershed of the Saskatchewan River System. Most of the rivers, except a few tributaries that arise in areas such as the Cypress Hills, originate along the mountain chain. These waters are of prime importance in the irrigation of 840,000 acres in southern Alberta and in the proposed irrigation of large tracts of land in southern Saskatchewan. The effects of grazing intensity on the water-intake characteristics of soils of the area have not been s t u d i e d previously. Work elsewhere has indicated that these effects may be important. D u 1 e y and Kelley (1939) found that the infiltration rate on native sod with a good cover was several times that of bare ground. In a further study, Duley and D o m in g o (1949) found that total cover including live grass and associated litter was more important than the kind of grass or the type of soil in inducing a high water-intake rate. Dyksterhuis and Schmutz (1947) noted that natural mulch was a primary factor in determining total annual infiltration of water into rangeland. Rauzi. (1960) found that the water-intake rate increased with an increase in the amount of natural mulch and standing vegetation. Alderfer and Robinson (1947) found runoff losses to vary from 0 to 2 percent on ungrazed range and from 33 to 80 percent on heavily g r a z e d range. Both Tomanek (1948) and Hopkins (1954) showed that a relationship exists between the amount of natural mulch and the moisture content of rangeland soils. The purposes of the study were to assess the effect of grazing by cattle on the water-intake rate of soils in the fescue grass1 a n d of southwestern Alberta and to determine the effect of various constituents of the vegetation cover on the water-intake rate.

Effect of Amount of Mulch on Soil Temperature and Early Growth of Corn1

SynopsisEarly growth of corn was progressively retarded by increasing amounts of mulch.

Effect of Tansy Mustard (Descurainia intermedia) on Moisture Storage during Fallow

C INCE the work of Cox and Cates (2) in 1912, it had been shown 3 repeatedly that weeds growing in competition with crops decrease yields. These results lead to the general assumption that weeds are detrimental anytime, including a fallow period for moisture conservation. In fact many farmers in the Great Plains area still plow during the winter or when there are no weeds to promote a dust for moisture conservation even though this practice has been shown to be of little value (6, 7). Recent research has shown that where runoff is prevented and weed control is adequate during the fallow period, type of tillage or amount of mulch does not greatly affect moisture storage in the Southern Great Plains (8). Finnell (5) stated that on the heavy soils of the Southern Great Plains 65.8 percent of the rainfall was evaporated, 13.5 percent was runoff, 2.7 percent was lost in tillage operations and 18.0 percent was stored in the soil.

The Mulch Layer of California Annual Ranges

T HE past few years of below average precipitation have emphasized the importance of a mulch layer on annual ranges in California. It has been apparent that where sufficient mulch was found germination was better, and early growth and total production of forage was greater than on ranges lacking enough mulch cover. It was observed also that where grazing animals had old forage in fall and early winter to eat along with the new, they scoured less and made better gains than where only new growth was available. ,4 mulch layer also helps to maintain the percolating capacity of soils and prevent erosion. In studying the mulch layer near Berkeley it was found that terminology applied to it varies among different workers (1, 4, 6, 7, 8, IO, 11, 12). In an attempt to standardize terms and classification of the mulch layer on annual ranges in accordance with present usage, the writer proposes adoption of the termsmulch, forage residue, and humic mulch. Applied in this way, mulch is a collective term which refers to the whole protective blanket of vegetation after the forage has dried. Forage residue includes all dried herbage of the past year’s growth that might be used for grazing. Humic mulch is used only in referring to semi-decomposed materials which constitute but a thin layer on the surface of the soil. Considerable work has already been done in determining the amount of forage residue which should be left on annual ranges to keep them in productive condition (6, IO, 13). This varies from about 400 to 1000 pounds per acre. However, few, if any, measurements of the humic mulch layer are available even though it has been used as an important factor in determining range condition (6, 7, 10, 12). Since humic mulch on annual ranges is so thoroughly mixed with mineral soil, separation of it is difficult and time consuming. Accordingly, some method other than those used in other forage types (4,9) had to be devised for measuring the effect of intensity of grazing on the humic mulch layer of annual ranges. Several workers have noted the increase in volume weight of soils brought about by grazing and cultural practices (2, 5). In view of these results it seemed reasonable to assume that measures of volume weight of thin layers of surface soil might give usable measurements of the amount of humic mulch. If so, the effect of intensity of grazing on humic mulch could be determined indirectly by sampling the top layer of soil. This was accomplished by using a loinch length of l+-inch water pipe sharpened on one end. After first clearing away green plants and residue, the sampling tube was sunk into the surface layer of soil to a depth of about 1 inch. Rotating the tube while sampling helped to avoid compaction and shear off the sample near the end of the cylinder. Volume of the sample collected was then determined by filling the hole with sand as described by Daubenmire (3). After drying in an oven for 24 hours at 105 degrees Centigrade, the samples were weighed and volume weights determined by the ratio of dry weight of soil and humic mulch in grams/volume in cubic

Microbiological Studies of the Effect of Straw Used as a Mulch

Microbiological Studies of the Effect of Straw Used as a Mulch, T. M. McCALLA2, U.S. Department of Argiculture and College of Agriculture, Lincoln, Nebraska Converting the land of the virgin forest and prairie to the production of cultivated crops has permitted the ravages of soil erosion by wind and water to deplete the fertility of many American soils (2). Recently, it has been found possible to lessen the soil deteriorating action of water and wind by leaving crop residues at the surface of the soil with a system of subsurface tillage (3, 4), rather than plowing under the residues or burning them. Duley and Russel (3) have shown that crop residues left on the surface of the soil reduce runoff and erosion to a high degree. It is possible by using a stubble mulch on the surface to protect land effectively against erosion while growing cultivated crops. The practice of leaving residues on the surface of the soil and cultivating underneath them is radically different from the conventional method of handling land in cultivated crops. However, it is not so different from the method employed by nature in returning residues from grasses or trees to the surface of the soil where the residues act as a protective mantle. Microorganisms in the soil bring about the decay of plant remains, produce humus, and convert the mineral elements of the organic matter to a soluble form. In order to know how the presence of a mulch affects the environment of the organisms, and hence their activities, the following points have been investigated: (A) moisture and temperature conditions, (B) soil populations, (C) amount and nature of mulch as influenced by decomposition, (D) decomposition products of soil microorganisms as they influence soil structure and water infiltration, and (E) production of soluble nitrogen. It seems desirable to consider the influence of straw mulch on the soil as a medium for biological activity in order to plan wisely a cropping sequence which will provide a mulching material, secure maximum soil protection, maintain or increase crop yields, and provide for maintenance of soil fertility.