Tillage and crop residue management affect Vertisol properties and grain sorghum growth over seven years in the semi-arid sub-tropics. 2. Changes in soil properties

Six treatments, disc (D), blade (B) or zero (Z) tillage, each with stubble (crop residue) retained (+) or removed (−), were imposed during fallow periods between annual grain sorghum crops from June 1978 to June 1985 on a grey Vertisol in the semi-arid sub-tropics of central Queensland. Plots were neither irrigated nor fertilized. Soil profiles for chemical analysis were sampled post-harvest and pre-plant after fallow. For surface soil (0–0.1 m and sometimes also 0.1–0.2 m) during the 7 years, net decreases were measured for organic and total carbon, total nitrogen, total bicarbonate extractable and calcium chloride extractable phosphorus, total sulphur, total and exchangeable potassium. Net increases were measured for exchangeable sodium, calcium and magnesium. No net changes were found for dispersion ratios and cation exchange capacity. A net decrease in nitrate at 0.6–1.6 m began after 3 years. At 0–1.6 m, changes in pH, electrical conductivity, chloride and ammonium were negligible.

General means at 0–0.1 m decreased annually from June 1978 by 3.9% for organic carbon, 3.1% for total nitrogen, 7.5% for bicarbonate extractable phosphorus and 10.0% for calcium chloride extractable phosphorus. Decreases in organic carbon and total nitrogen had similar trends for each tillage treatment, being greater with stubble removed than with stubble retained. Decreases were least for Z+. After five years the increase in exchangeable sodium was highest for Z−. The pattern for each tillage treatment was for higher exchangeable calcium and magnesium at 0−0.1 m and higer exchangeable potassium at 0–0.02 m with stubble retained than with stubble removed. After 7 years the silt + clay dispersion ratio was lower for Z+ and Z− than for the other treatments.

There was an average net gain of 30 kg ha⁻¹ of nitrate-N at 0–0.6 m during fallow periods followed by a similar loss during cropping periods. Nitrate at the end of the fallow was equally distributed at three depths: 0–0.1, 0.1–0.2 and 0.2–0.6 m. On two occasions after a crop, the pattern was less nitrate (0–0.6 m) with stubble retained than with stubble removed, the difference for each tillage treatment increasing in the order D−1) ranged from 62 kg N ha⁻¹ for Z− to 128 kg N ha⁻¹ for Z+. The decrease for all tillage treatments was greater where stubble was retained than where it was removed. Decreases where stubble was retained were in the order D相似文献   

Tillage and crop residue management affect Vertisol properties and grain sorghum growth over seven years in the semi-arid sub-tropics. 3. Crop growth, water use and nutrient balance

The effects of fallow surface management treatments on subsequent growth and yield of grain sorghum were studied during seven cropping periods on a grey Vertisol near Biloela in central Queensland, Australia. Treatments were disc (D), blade (B) and zero (Z) tillage, each with stubble or residue from previous crops either retained ( + ) or removed ( − ) at the start of the fallow period. Treatments were planted to grain sorghum between December and February, following a 7–8 month fallow period.

Plant establishment was significantly (P<0.05) lower in Z than in D and B treatments in five of the seven crops. Average plant establishment over 7 years was about 20% lower in Z treatments. Early crop growth was generally more vigorous in D and B than in Z treatments, but this trend became less pronounced at later stages of growth. Surface cover (stubble+crop) ranged from 46% in Z + to 26% in Z− 5 weeks after planting and from 68% to 57% at anthesis and 62% to 46% at maturity in these same treatments. For the seven crops, annual mean grain yields over all treatments ranged from 1650 to 4490 kg ha⁻¹. Z− had a significantly (P<0.05) lower mean grain yield over the seven crops than all other treatments, which did not differ significantly (P>0.05). Where stubble was retained, yields of D+ and B+ never differed significantly. However, yields from Z+ were significantly higher in three crops than those from D+ and B+ and lower in three other crops. Stubble retention consistently resulted in significantly higher yields than stubble removal in the Z treatment. Crop water use was consistently lower in Z− than in all other treatments. Of the total roots to a depth of 1.6 m, a mean of 28% were found at 0–0.1 m. At 0.1–0.2 m and in deeper 0.2 m increments, the mean ranged from 6 to 11%.

Over 7 years, decreases in soil organic carbon at 0–0.1 m with stubble retained were less than with stubble removed. The differences corresponded to 4.1, 10.0 and 6.2% of stubble carbon inputs in D, B and Z treatments, respectively. Nitrogen removal in grain and stubble, expressed as a fraction of soil total nitrogen at 0–0.2 m plus nitrate-nitrogen at 0–1.6 m, ranged from 43% for D+ to 82% for Z+. Decreases of bicarbonate- and acid-extractable phosphorus at 0–0.1 m each corresponded to between 31 and 50% of the phosphorus removal in grain and stubble.     

Crop residue management and tillage methods for conserving soil and water in semi-arid regions

Soil degradation reduces soil productivity and is a serious problem on much of the land in semi-arid regions. To avert continued degradation, the soil productivity balance must be shifted from degrading processes to conservation practices. Crop residue management and conservation tillage are on the positive side of the balance. When adequate residues are available and conservation tillage is used, soil erosion is greatly reduced and water conservation is enhanced. Water conservation is important for improving crop yields in semi-arid regions, especially where irrigations is not used. A major constraint to residue management in many countries is low production and widespread use for other purposes. In such cases, clean tillage and appropriate support practices such as contouring, furrow diking, strip cropping and terracing may provide adequate soil and water conservation benefits. Where these are not adequate, alternative management practices should be implemented to ease the demand for residues, thus permitting more of them to be retained on the land for soil and water conservation purposes. Some alternative practices include limited or selective residue removal, substituting high quality forages for residues as animal feed, alley cropping, using wasteland areas more effectively, improving the balance between feed supplies and animal populations, and using alternative fuel sources.     

Tillage practices for soil and water conservation in the semi-arid zone I. Management of fallow during the rainy season preceding cotton

Field and laboratory experiments were conducted on a crusting loess soil in the northern Negev (Israel) with the aim of improving the efficiency of the use of rain by row crops, either in dryland or irrigated farming, and to decrease erosion. The specific objective of the experiments described was to develop methods that enhance infiltration of rainfall during the winter fallow season in an area with a mean annual rainfall of 400 mm which is subject to wide variation.It was found that the traditional tillage system consisting of deep ploughing (35–45 cm) of dry soil in the fall followed by disking, smoothing and ridging is the worst choise as it could result in runoff losses of as much as 60% of the rainfall, accompanied by accelerated erosion. This water loss can be critical to the success of dryland cotton and also determines whether or not a pre-irrigation of about 25% of the total annual water allotment must be given to irrigated cotton.The traditional practice was compared with: deep ploughed land left fallow during the entire rainy season; ridging after subsoiling instead of deep ploughing; subsoiling and ridging carried out in one minimum tillage operation; direct ridging without primary tillage and basin tillage of ridges following either deep ploughing, subsoiling or minimum tillage.This study showed that by far the most effective method for enhancing infiltration and eliminating runoff was the basin tillage system. The method is adaptable both to mechanized farming and to farming based on animal power or manual labour, and its application can ensure success where rainfall is limiting.It was found that laboratory characterization of soil hydraulic properties with a static rainfall simulator allows prediction of runoff on crusting soils. This means that the need for, and the effectiveness of, conservation measures may be estimated using disturbed soil samples, which is quicker and cheaper than field tests.     

Relationships between abiotic and biotic soil properties during fallow periods in the sudanian zone of Senegal

Relationships between soil characteristics, various forms of soil organic matter, microbial biomass and the structure of phytoparasitic nematode populations were investigated in six fallow fields aged from 1 to 26 years in the West African Savanna (WAS) belt in southern Senegal. Soil sampling was performed along two transects in each field. Herbaceous biomass and soil physical, chemical and biological characteristics were studied with principal component analysis (PCA) and the relationships between the parameters were extracted with co-inertia analysis.Soil properties (mainly calcium, magnesium and total carbon contents, and cation exchange capacity) slightly improved in the upper soil layer (0–5 cm) during the succession of vegetation. In constrast, in the 0–10 cm soil layer, microbial biomass and total soil organic carbon content showed no clear pattern of change over time, while highest charcoal stocks were found in older fallows where bush fires are frequent. In the 0–40 cm layer, living root biomass increased and herbaceous biomass decreased through the chronosequence. Evidence is presented here for particular relationships between some of the carbon components and the structure of the nematode community. Pratylenchus and Ditylenchus species were associated with the grass vegetation of the youngest fallows. In contrast Helicotylenchus and Scutellonema were present in old fallows. The multiplication of the latter appeared closely related to the presence of woody fine roots, whereas, that of the former seemed to be favoured by the presence of the coarsest roots of trees.Xiphinema had a higher density in soils with higher bulk density. Microbial biomass was not affected by fallow duration and was not correlated with the abundance of non-phytoparasitic nematodes. These results suggested that the management of crop pests such as nematodes in the soils of the WAS could be exerted through stump protection and tree plantation (improved fallow, agroforestry) during the crop-fallow cycle.     

Tillage effects on water storage during fallow, and on barley root growth and yield in two contrasting soils of the semi-arid Segarra region in Spain

In semi-arid areas under rainfed agriculture water is the most limiting factor of crop production. To investigate the best way to perform fallow and its effect on soil water content (SWC) and root growth in a barley (Hordeum vulgare L.) crop after fallow, an experiment was conducted on two soils in La Segarra, a semi-arid area in the Ebro Valley (Spain). Fallow was a traditional system used in these areas to capture out-of-season rainfall to supplement that of the growing period, usually lasting 16 months, from July to October of the next year. Soil A was a loamy fine Fluventic Xerochrept (Haplic Calcisol, FAO) of 120 cm depth and Soil B was a loamy Lithic Xeric Torriorthent (Calcaric Regosol, FAO) of only 30 cm depth. The experiment was continued for four fallow-crop cycles in Soil A and for two in Soil B. In Soil A, three tillage systems were compared: subsoil tillage (ST), minimum tillage (MT) and no-tillage (NT). In Soil B, only MT and NT were compared. In the fields cropped to barley, SWC and root length density (LV) were measured at important developmental stages during the season, lasting from October to June. In the fallow fields SWC was also monitored. Here, evaporation (EV), water storage (WS) and water storage efficiency (WSE) were calculated using a simplified balance approach. The fallow period was split in two 8-month sub-periods: July–February (infiltration) and March–October evaporation (EV). In Soil A, values of WSE were in the range 10–18% in 1992–1993, 1993–1994 and 1994–1995 fallow, but fell to 3% in 1995–1996. Among tillage systems, NT showed significantly greater WSE in the July–February sub-period of 1992–1993 and 1993–1994 fallow, but significantly lower WSE in the March–October sub-period, due to greater EV under NT. Consequently, no differences in total WSE were found between tillage systems. In Soil B, WSE was low, about 3–7%, and there were no difference between tillage systems. During the crop period, the differences in SWC and LV between tillage systems were small. Regarding yields, the best tillage system depended on the year. NT is potentially the best system for executing fallow, but residues of the preceding crop must be left spread over the soil.     

Tillage and crop residue management significantly affects N-trace gas emissions during the non-rice season of a subtropical rice-wheat rotation

Field operations of tillage and residue incorporation could have potentially important influences on N-trace gas fluxes, though poorly quantified. Here we studied the effects of straw incorporation in the preceding rice season and no-tillage prior to wheat sowing on nitric oxide (NO) and nitrous oxide (N₂O) emissions during the non-rice period of a typical rice-wheat rotation in the Yangtze River Delta. Compared to conventional management practice (no straw incorporation along with rotary harrowing tillage to 10 cm before wheat sowing), straw incorporation alone decreased cumulative N₂O emissions over the entire non-rice period by 32% (1.53 vs. 2.24 kg N ha^-1, P < 0.05) but did not affect NO emissions (0.88 vs. 0.87 kg N ha⁻¹). In contrast, no-tillage alone increased N₂O emissions by 75% (P < 0.05) while reducing NO emissions by 48% (P < 0.01). Combination of no-tillage and straw incorporation led to no change in N₂O emissions but a reduction in NO emissions compared to the conventional management regime. The direct N₂O emission factors (EF_ds) of applied nitrogen fertilizers during the non-rice season ranged from 0.29% to 1.35% with a coefficient of variation (CV) as large as 68% among the investigated management regimes. The EF_ds for NO ranged from 0.13% to 0.32% with a CV of 50%. Adoption of these new EF_ds will allow us to account for management effects on N-trace gas emissions when calculating emission inventories. Nevertheless, it is noteworthy that the uncertainty remains high, since the effects of soil properties such as texture or pH on management practices are not yet well defined.     

Tillage practices for soil and water conservation in the semi-arid zone II. Development of the basin-tillage system in wheat fields

In the northern Negev of Israel, a typical semi-arid region with a Mediterranean rainfall pattern, wheat production is limited mainly by the amount of available water. Despite the common occurrence of drought years, storm runoff coefficients for unit areas may reach 30–50% of rainfall. Runoff is the main cause of serious erosion damage consisting of soil loss, gully development and loss of productivity.The system of tied ridges or basin tillage, which effectively eliminated over 90% of runoff and erosion in fallow fields before cotton, appears to be a promising solution to the problem of both soil and water conservation in drilled crops as well. Analysis of the long-term rainfall record of the region and the predicted runoff indicates that the basin-tillage system can decrease runoff by at least 50% as compared with the conventional planting system. Experiments carried out during the 1980–1981 rainy season proved that even in a relatively dry year the basin tillage system was effective in increasing wheat yield by about 50% and eliminating erosion.     

Development and evaluation of a soil water evaporation model to assess the effects of soil texture, tillage and crop residue management under field conditions

Abstract. A number of mathematical models to predict soil water evaporation are available in the literature which generally require complex input data. In the present study, a simple parametric model has been developed by coupling existing and newly developed equations to assess soil water evaporation and drainage under field conditions in relation to potential evaporation rate, soil texture, time and depth of tillage and crop residue management. The model has moderate input data requirements and predicts well the effects of tillage and crop residue management practices on soil water loss (evaporation+drainage) with multi-drying and -wetting cycles prevailing under natural conditions. The root mean squares of deviations between observed and predicted cumulative water loss at different periods of study were 0.82, 2.04, 2.31 and 1.74  cm for untreated, residue-mulch, tillage and residue-incorporated treatments, respectively. Simulation analysis on cumulative evaporation and evaporation rate has shown that the evaporation reduction with different combinations of tillage and crop residue followed the order of residue-undercut>residue-mulch>residue-incorporated>tillage. Thus, the magnitude of beneficial effects of crop residues and tillage on soil water evaporation reduction are associated with amount of residues, mode of residue management (mulched or incorporated in the soil) and time and depth of tillage.     

Tillage practices for soil and water conservation in the semi-arid zone III. Runoff modeling as a tool for conservation tillage design

A method of runoff calculation and prediction has been developed, based on known soil properties and a probability analysis of historical rainfall data. The method provides an evaluation of the efficiency of any tillage system for conserving runoff water. It consists of four steps: (1) the infiltration characteristics of a particular soil type under a given management regime are determined with the aid of a portable rainfall simulator; (2) the long-term record of actual rainfall of the region is analyzed for storm intensity distribution; (3) runoff amounts and rates are calculated for all rain storms on record by a method which combines the soil infiltration function and storm intensity pattern; and (4) synthetic long-term runoff values are predicted by calculations based on the rainfall probability distribution.The method was verified by comparing predicted results with available data from field experiments. In addition to predicting the probability of runoff under given soil conditions, the method is useful in providing information on the amount of surface storage required for successful performance of the basin tillage (tied-ridge) system, and aids in the evaluation of the efficacy of measures for improving soil infiltrability, e.g., of amendments such as gypsum.     

Evaluation of fly ash as a soil amendment for the Atlantic Coastal Plain: II. Soil chemical properties and crop growth

Crop yields in the Atlantic Coastal Plain of the U.S.A. are limited by the low moisture-holding capacities of the sandy soils common to the region. Corn was grown in a Hammonton loamy sand soil amended with fly ash (0, 5, 10, 20, 30, and 40%) to determine if the ash rates required to improve soil moisture holding capacity would adversely affect plant growth, or soil and plant levels of nutrients and heavy metals. Fly ash increased soil test levels of P, K, Ca, Mg, Mn, Cu, Zn, B, Cd, Cr, Ni, and Pb. Nutrient concentrations in plants grown in the ash-amended soils, except P, Mn, and B, remained within established sufficiency ranges. The 20 and 40% ash rates increased soil soluble salt (EC) levels from 0.2 to 1.1–1.5 and 1.7–2.1 mmho cm^?1, soil pH from 5.6 to 6.0–6.4 or 6.3–6.9, and extractable B from 0.2 to 2.2–5.9 and 2.2–9.0 mg kg^?1. Fly ash reduced corn germination, delayed seedling emergence, and reduced root and shoot dry weights. Plant B concentrations at the 40% ash rate were in the phytotoxic range (136–189 mg kg^?1). Management practices that allow for pre-leaching of B and soluble salts will likely be required to attain satisfactory corn growth in ash-amended soils.     

Smoke‐water and karrikinolide (KAR1) foliar applications promote seedling growth and photosynthetic pigments of the biofuel seed crop Jatropha curcas L.

This greenhouse study tested the effect of smoke‐water and the smoke‐isolated biologically active compound karrikinolide (KAR₁) on growth and photosynthetic pigments of Jatropha curcas L. seedlings. Fifteen‐day‐old seedlings were sprayed once weekly for 5 weeks with three dilutions of smoke‐water (1 : 250, 1 : 500, and 1 : 1000 v/v) or KAR₁ (10^–7, 10^–8, and 10^–9 M). Growth parameters and photosynthetic pigment concentrations of 75‐d‐old seedlings were measured. Foliar application of both smoke‐water and KAR₁ on J. curcas seedlings showed significant increases in stem width, shoot length, chlorophyll a, chlorophyll b, total chlorophyll, and total carotenoid concentrations compared to the untreated control. KAR₁ significantly improved leaf area, shoot and root dry mass, seedling‐vigor index, and photosynthetic pigments as compared to control treatments. These results suggest the possible use of smoke‐water and KAR₁ to achieve a vigorous and well established crop of J. curcas.