Effective Rooting Depth Research Articles

An Irrigation Scheduling Model for Summer Squash

An irrigation scheduling model for summer squash (Cucurbita pepo L.) was developed and validated during 1986, 1987, and 1989. The model is represented by the equation: 12.7(i - 4) × 0.5ASW = Di-1 + [E(0.14 + 0.015) - P - I]i, where crop age in days is i; effective root depth is 12.7(i - 4) with a maximum of 381 mm; usable water (cubic millimeter per cubic millimeter of soil) is 0.5ASW, deficit on the previous day is Di-1; evapotranspiration is pan evaporation (E) times 0.14 + 0.015i; rainfall (in millimeters) is P; and irrigation (in millimeters) is I. The model was validated during the three years using a line-source irrigation system with irrigation depths ranging from 5% to 160% of the model rates. Nitrogen rates were 50%, 100%, and 150% of the recommended rate. Marketable fruit yields increased as the irrigation depths increased up to the model rate then decreased with greater water application depths. Marketable fruit yields increased as the N rate increased in 1987 and 1989, but yields were similar at all N rates in 1986. The shelf life of marketable fruits was not influenced by irrigation or N rates.

Effect of limited irrigation on growth and yield of a semi-dwarf wheat in southern New South Wales

The semi-dwarf wheat cv. Egret, was subjected to moisture stress at specific growth stages in a field experiment in the Murmmbidgee Irrigation Area of New South Wales. The 6 treatments ranged from natural rainfall (129 mm of effective rainfall) to flood irrigations in the spring. Moisture stress during spike emergence and anthesis reduced yield from 7.0 to 3.3 t/ha through reductions in spikesJm2 (37%), individual grain weight (15%) and grain number per spike (13%). Stress during grain filling reduced yield by 20% mainly through a 16% reduction in individual grain weight. Irrigation treatment also significantly influenced dry matter production, plant height, leaf area, duration of grain filling and grain protein. Where irrigation water supply is limited, the best strategy would be avoidance of moisture stress during tillering through to spike emergence. An effective rooting depth of 70-80 cm was extended to >110 cm under severe moisture stress during grain filling, but at the expense of considerable yield.

A Field Guide to Site Quality for the Allegheny Hardwood Region

Abstract A site quality evaluation technique using soils and topographic criteria is presented. The field guide, developed in the unglaciated, deeply dissected Allegheny Plateau region of southwestern New York and in northcentral and northwestern Pennsylvania, is currently being used by International Paper foresters on company property within that region. A different set of decision criteria and site quality weightings is applied for each of four topographic units: (1) plateau tops (≤15% slope) and side slopes < 10%, (2) upper slopes (>9% slope), (3) middle slopes (>9% slope), and (4) lower slopes (>9% slope). Decision criteria are all field determinable and include: soil texture, soil stoniness, aspect, shade angle, slope shape, and effective rooting depth. Points are awarded so that relative site quality ratings from 40 to 100 are scored. Site I, II, and III designations are assigned to site quality ratings of 80-100, 60-79, and 40-59, respectively. North. J. Appl. For. 8(1):3-8

AN IRRIGATION SCHEDULING MODEL FOR TURNIP GREENS

An irrigation scheduling model for turnip greens (Brassica rapa L.) was developed and validated.. The irrigation scheduling model is represented by the equation: 12.7 (i-3) * 0.5 ASW = 0i-1 + Ei(0.365+0.00154i+0.00011i2) - R - I where crop age is i; effective root depth is 12.7 * (i-3) with a maximum of 300 mm; usable water (cm/cm of soil) is 0.5 ASW; deficit on the previous day is Di-1 evapotranspiration; is pan evaporation (Ei) times 0.365+0.0154i+0.00011i2; rainfall (R) and irrigation (I) are in millimeters. Yield measured as leaf weight, and quality analyzed in terms of color (Gardner XL20 cronameter L, a, b), leaf blade and blade: stem weight ratio were determined. Leaf yield and quality responses were affected by both irrigation and fertilizer rates. Yield increased quadratically as irrigation rates increased from 0 to 190% of the model rate. Maximum leaf yields were produced by irrigations at 100% of the model rate. Leaf quality parameters also tended to change quadratically with irrigation rates. Leaf yield and quality changed quadratically as nitrogen fertilizer rates increased from 80 to 120% of the median recommended N rate for Georgia.

Interpretation of Environmental Gradients Which Influence Sagebrush Community Distribution in Northeastern Nevada

Sagebrush stands on the Humboldt National Forest, northeastern Nevada, were classified by two-way indicator species analysis (TWINSPAN) into 15 community types. Detrended correspondence analysis (DECORANA) was used to ordinate samples and plant species and characterize environmental gradients regulating community structure. Regression of soil attributes with sample ordination scores suggested that the plant communities respond to a complex gradient involving soil depth, water holding capacity, mollic epipedon thickness, clay content, and effective rooting depth. Soil chemical properties which displayed significant correlations with sample ordinations included pH, base saturation, calcium, total nitrogen, organic matter, and phosphorus. These soil properties are considered to either directly influence or indirectly reflect the available soil moisture of a site. The transition from black sagebrush (Artemisia nova Nels.) to low sagebrush (A. arbuscula Nutt.), basin big sagebrush (A. tridentata Nutt. ssp. tridentata) and mountain big sagebrush (A. tridentata Nutt. ssp. vaseyana) stands along DECORANA Axis 1 appeared to represent a gradient of increasing available soil moisture. Elevation and aspect were not correlated with sample ordination scores. This lack of correspondence is presumably due to various soil properties (e.g., depth, rock content, texture) which modify the direct effects of elevation and aspect on available soil moisture.

An Irrigation Scheduling Model for Snap Bean

An irrigation scheduling model for snap bean (Phaseolus vulgaris L.) was developed and validated. The irrigation scheduling model is represented by the equation: 12.7(i - 4) × 0.5ASW = Di-1 + [E(0.31 + 0.01i) - P - I]i, where crop age is i; effective root depth is 12.7(i - 4) with a maximum of 400 mm; usable water (cm3·cm-3 of soil) is 0.5 ASW, deficit on the previous day is Di-1; evapotranspiration is pan evaporation (E) times 0.31 + 0.01i; rainfall (mm) is P, and irrigation (mm) is I. The model was validated using a line source irrigation system with irrigation depths ranging from 3% to 145% of tbe model rate in 1985 and from 4% to 180% of the model rate in 1986. Nitrogen fertilization rates ranged from 50% to 150% of the recommended rate both years. Marketable pod yields increased as irrigation rate increased in 1985. Irrigation at 4%, 44%, 65%, 80%, 150%, and 180% of the model rate produced yields that were 4%, 39%, 71%, 85%, 92%, and 55% as great as yields with the model rate in 1986. Marketable pod yields increased as N rate increased when irrigation was applied at 80%, 100%, or 150% of the model rate in 1986, but pod yields varied less with N rate when irrigation was applied at 4%, 44%, 65%, or 180% of the model.

Associations Between Productivity, Root Growth and Carbon Isotope Discrimination in Phaseolus vulgaris Under Water Deficit

Recent theoretical and empirical studies have indicated that isotopic discrimination against 13C (Δ) during photosynthesis in C3 plants reflects variation in intercellular CO2 concentration (ci). Under water deficit, cultivar differences in Δ may indicate differences in leaf gas exchange characteristics. Cultivar differences in Δ may also result indirectly from genetic variation in root characteristics affecting the level of water stress experienced by the canopy. Differences in root growth affecting the degree of dehydration postponement could prolong gas exchange activity and the maintenance of relatively high ci and Δ. To evaluate relations between root growth, productivity and Δ in common bean (Phaseolus vulgaris L.), Δ and crop growth parameters, including biomass production, grain yield and root length density, were determined for ten bean genotypes grown under rainfed conditions at two sites in Colombia which differed primarily in soil fertility and effective rooting depth. The 10 genotypes were also grown under irrigation at the more fertile site. Under rainfed conditions, root length density was positively correlated with Δ in the fertile Mollisol at Palmira, and was also positively correlated with Δ in the infertile Oxisol at Quilichao if one possibly abberent genotype was excluded. At Palmira, reduced crop growth and seed yield were associated with low Δ values. At Quilichao, intermediate Δ values were associated with the greatest growth and yield. Under irrigation at Palmira there was no association between growth or yield and Δ.

EXPERT SYSTEM-BASED COUPLING OF SOYGRO AND DRAINMOD

ABSTRACT A combined crop growth (SOYGRO 5.4) and water management (DRAINMOD 3.4) modeling system was developed using an expert system shell to coordinate input and output between the models. An iterative simulation procedure was used to keep the models intact and modular for inclusion of additional crop growth, pest, economic, and environmental impact models in the future. DRAINMOD 3.4 was modified to accept evapotranspiration and effective rooting depths from SOYGRO and allow feedback control. The feedback control system performed satisfactorily. SOYGRO 5.4 was enhanced to accept from DRAINMOD water movement due to upward flux from a water table. In addition, the model was modified to account for the crop stress due to oxygen deprivation caused by a water table extending into the rooting zone. Simulated soybean yields and root length densities were greatly affected by a raised water table and by climatic variations for the tested conditions. However, if the water table was maintained within 90 cm of the soil surface during the entire growing season, weather patterns had only a minor influence on root length densities and yield.

Root distribution of lychee trees growing in acid soils of subtropical Queensland

A core sampling technique was used to investigate the vertical root distribution of 8-10-year-old lychee trees (Litchi chinensis cv. Tai So) growing on 5 acid soils in subtropical Queensland (lat. 27�s.). At each site, soil and roots were sampled at 10 cm depth intervals to 100 cm, the root density determined and a range of soil chemical and physical properties measured. Eighty percent of the feeder roots were located within the top 0-20 cm (1 site), 0 4 0 cm (2 sites) or 0-60 cm (2 sites). The depth of rooting was greatest in the fine textured soils, while the greatest total root density was recorded in the coarse textured soils. The data suggest that the placement of tensiometers for water scheduling needs to take into account the effective rooting depth of lychee because it may vary with soil type. At all sites, pH values were acidic (pH<6.0) and subsoil pH values were below 5.5, and exchangeable Ca decreased and exchangeable A1 increased with depth. Four of the 5 sites had subsoil with >30% Al saturation of the cation exchange capacity. Although root density (all sites) was correlated with a number of soil chemical properties, stepwise multiple linear regression showed that 62% of the variation in root density could be explained by a curvilinear function of depth. The intercorrelations between soil properties and the correlation of depth with some properties demonstrate the difficulties in separating the effects of depth per se from those of soil properties in reducing root growth.

Hydrology of a tropical rain forest in Surinam.

Rainfall and discharge were measured for almost 5 years in a 300 ha forested watershed in Surinam. Groundwater levels were measured for 2 years. The hydrological data were used in a simulation model for plant growth. Estimates were made on effective rooting depth, transpiration reduction in the dry season, and the contribution of interception to total water use. Possible relations between hydrological characteristics of the forest and nutrient cycling are given. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Fertilising Commercial Forest Species in Southern Africa: Research Progress and Problems (Part 1)

SYNOPSIS Since the inception of forest fertiliser research in Southern Africa in 1926, eight eucalypt, six pine and four acacia species have been tested, encompassing a wide range of sites in summer, winter and uniform rainfall areas. Marked deficiencies of P, Mn and sometimes N, usually associated with hydromorphic and elluviated soils derived from sandstone, are easily diagnosed and corrected at planting or after canopy closure. On the other hand, ferralitic soils showing adequate growth rates respond mainly to applications of P and Ca but balanced for N and K at planting. However, requirements after canopy closure are difficult to determine, varying with site, species and stand development. Fertilising at planting promotes the development of a vigorous root system, which allows for continually improved growth. Thus responses increase with the effective rooting depth and soil water availability of sites, as well as being larger for the faster growing species. Hence MAI has been increased up to 11 m3/ha ...

Quantification of accelerated soil erosion using the environmental tracer caesium‐137

AbstractThe principal objective of this investigation was to quantify erosion rates for five agricultural fields in three separate study areas in Saskatchewan. The radionuclide tracer caesium‐137 (137Cs) was used to quantify net erosion and net deposition within the landscape over a 30‐year period. Uneroded (native) sites were used to establish the mean background level of 137Cs in each of the study areas. The assumption being that agricultural sites with 137Cs areal activities greater than the native site were subject to deposition, and sites with 137Cs less than the native control site were subject to erosion. A linear proportionality model was used to convert the loss or gain of 137Cs to net soil erosion or deposition. Results have indicated that accelerated (anthropogenic) erosion has been commonplace on arable land in Saskatchewan, even on near‐level fields (< 1.3 degrees). The net integrated sediment output from the five agricultural fields ranged from — 0.6 t th−1 y−1 to — 6.8 t ha−1 y−1 (where negative values represent erosion). What is more alarming is that between 40 and 75 per cent of all sites sampled within individual fields had erosion rates in excess of the generally accepted rate of soil formation (1.0 t ha−1 y−1). Also, in one highly eroded field (Crystal Springs medium sloping site) 65 per cent of the sites sampled exceeded the upper tolerable erosion rate of 11.0 t ha−1 y−1. These results indicate significant degradation of the non‐renewable soil resource has occurred over the past 30 years and is still presently active. Land degradation by accelerated erosion would result in reductions in effective rooting depth, soil moisture holding capacity, essential nutrient stores, and would adversely effect the physical structure of the topsoil. The major reason for accelerated erosion on arable land in Saskatchewan is the practice of summer fallowing, where the field is left in a ‘bare’ state and repeatedly tilled every second or third year. During a fallow period, or prior to crop emergence during a cropping year, fields are subject to wind and water erosion. On near‐level fields wind would be the dominant transport agent, while on sloping fields inter‐rill and rill erosion would be the primary forces of erosion. It is suggested that the appropriate conservation farming response would be to increase application of surface mulches and possibly to decrease the frequency of summer fallowing. Without such efforts long‐term sustainable agricultural production in the Prairies of Canada is considered to be a tenuous land use practice.

Estimates of effective rooting depth for predicting available water capacity of burdekin soils, Queensland

Estimates of rooting depth are necessary parameters in predicting available water capacity (AWC) of soils. In a recently assembled database for the Burdekin River Irrigation Area, no single criterion, commonly used to estimate rooting depth, was available for all sites. Therefore a number of methods of estimating rooting depth which give interchangeable results were required. This paper compares eight methods of estimating rooting depth within three AWC models and compares the outcome with field determinations. Soil properties used to estimate rooting depth were laboratory-based (two chloride methods, electrical conductivity and pH), morphological (carbonate and mottling) and two fixed depths (0.9 and 1.0 m). For all soils tested, the laboratory-based methods used within one AWC model (based on regression equations by using -1500 kPa water retained) resulted in predicted AWC values not significantly different (P< 0.05) from field measurements. The suitability of mottling was limited to cracking clays and sodic duplex soils and other rooting depth methods had varying applicability depending on soil type. This work shows that a range of rooting depth methods can be used to predict AWC of Burdekin soils. The results should have application to soils of other areas.

Water use and water‐use efficiency of perennial ryegrass swards as affected by the height and frequency of cutting and seed rate

AbstractThe effects of cutting height (20 and 44 mm), frequency (once every 2 weeks April‐September inclusive and twice a year) and seed rate (250 and 20 kg ha‐1) on the water use and herbage yield of perennial ryegrass swards, for 3 years after sowing, were compared.Frequent cutting and a low cutting height reduced water use in the first year only. In later years infrequent cutting led to higher yields and higher water‐use efficiencies, but did not affect total water use or the shape of the soil water profile. Seed rate influenced sward composition and the pattern of water use, but not total water use. The swards from the low seed rate had a lower stubble biomass and tiller density, and extracted relatively more water at depths of 75 and 85 cm and less at depths of 15 and 35 cm, than the swards derived from the high seed rate.The ratio of actual: potential evapotranspiration was reduced as the soil water deficit increased and was lowest in the summer after a dry spring. Cutting height and frequency during summer were shown not to be effective methods of either conserving water or manipulating the effective rooting depth of an established sward.

Comparison of models for predicting available water capacity of burdekin soils Queensland

Various models for predicting profile available water capacity (PAWC) from laboratory measurements were compared with published field values for the same sites. The intention was to choose the best model/s to predict PAWC, by using a database, for a wide range of soils in the Burdekin Irrigation Area, North Queensland. Effective rooting depth for all models was estimated from the chloride profile. It was found that the predictive abilities of all models used were dependent on soil types. A conventional model (ASWC) based on the difference between water retained at -33 and -1500 kPa matric potentials was higher (P < 0.01) than field measured PAWC. An empirical model (PAWC2) based on cation exchange capacity (CEC) and depth was suitable only for cracking clays and sodic duplex soils. Another empirical model (PAWC1) based on -1500 kPa water retained and depth, predicted field PAWC particularly well on cracking clays, sodic duplex and related soils. There were strong indications that the PAWC1 model is also suitable for the better drained, lighter textured soils but there was a shortage of comparable field data to confirm this. The practical implication of these findings was that an analytical database can be used to predict PAWC on many Burdekin soils, providing immediate assistance to those designing irrigation channels and farm layouts.

Predicting Seasonal Irrigation Water Requirements on Coarse-Textured Soils

ABSTRACT Awater-balance model has been developed for predicting seasonal irrigation water requirements. The model treats the soil as a multi-layered water storage reservoir. Reservoir capacity is defined by soil water desorption data, rate of root growth, and effective rooting depth. Water withdrawal rate or crop water use is determined from pan evaporation data corrected to potential ET and converted by consideration of plant growth stage. Rainfall is partitioned into runoff, effective precipitation, and deep percolation. Field data from corn and soybeans during the seasons 1979-81 on two soil types were used for verification. The mean absolute difference between predicted and measured seasonal irrigation water requirements was 16%. Simulation data were fitted to frequency distributions, and irrigation requirements are expressed in terms of probabilities.

The effect of a ploughpan in marine loam soils on potato growth. 1. Physical properties and rooting patterns

The ploughpans studied on old land had a very small number of large pores, a large penetration resistance and a diminished aeration. On recently reclaimed land a very weak ploughpan was present but a severe ploughpan with similar characteristics as on old land could be established relatively easily. A too high mechanical impedance has to be considered as the primary factor severely hampering root growth in these ploughpans. Especially in a relatively dry growing season, water supply to the root system, therefore, was clearly suboptimal. Removal of the ploughpan on old land only slightly increased the effective rooting depth because of a hardly rootable subsoil. Roots easily penetrated the subsoil on new land.

Site Requirements for Commercial Afforestation in the Cape

SYNOPSIS General guidelines for the mapping of forest sites in the Cape suggest that a soil based resource inventory at a field mapping scale of 1:10 000 may offer the best compromise for selection of species. The soil requirements at the form level for Acacia melanoxylon, Eucalyptus diversicolor, Pinus elliottii, P. patula, P. pinaster, P. radiata and P. taeda are given for the eastern, southern and western Cape. The influence of soil morphology, indicator species, leaching status, effective rooting depth, available phosphate, exposure to winds and other adverse climatic conditions on the yields of these species is indicated in relative terms.

The structural improvement of damaged clay subsoils

SummaryA manually damaged, smeared layer (pan) was created at plough depth in two clay soils. Soil physical properties, soil water regimes and plant responses were measured in panned and non‐panned soil from 1972 to 1975. Continuity of the pan was readily lost on drying by formation of shrinkage cracks which did not fully close unless the soil had been wet for a long time; thus the occurrence of perched water tables above the pan was rare. The pans had no effect on crop yields. Leaf water potential, effective rooting depth and subsoil water deficits all showed that the pans affected water uptake by roots, but these effects were transient. The results indicate that natural amelioration of pans in these clay soils occurs even after slight drying and that the degree but not duration of drying is important.

Distribution of Crumenulopsis sororia (Karst)

A study was made of the canker pathogen Crumenulopsis sororia in ten stands of Lodgepole pine (2825 trees) at Mearns Forest, Grampian Region, Scotland. The stands sampled were all of Alberta provenance and ranged from 46–50 years old. In heavily infected stands co- and subdominant trees were more extensively cankered than were dominant and suppressed trees, whereas the extent of cankering and resinosis was not related to stem girth-class. Significantly (p = 0.001) greater numbers of cankers occurred on north and east facing sides of tree stems as compared with south and west sides. The use of Weighting Coefficients to integrate severity of infection with stage of disease showed that suppressed trees scored highest disease indices and that there were significant (p = 0.01) differences in disease indices between the dominant, codominant and suppressed classes. Percentage infection of Lodgepole pine by Crumenulopsis sororia was correlated negatively with effective rooting depth (r=−0.66) and positively with percentage soil moisture (r=+0.91). These findings suggest that limited rooting volume and variations in the micro-climatic regime around individual stems may influence critically the success of infection.