水稻田间育秧精密播种机设计与试验     

马旭  邝健霞  齐龙  梁仲维  谭永炘  江立凯 《农业机械学报》2015,46(7):31-37

为提高田间育秧播种机的播种合格率和播种稳定均匀性,设计了一种适用于南方水稻田间育秧的精密播种机。在深入分析螺旋勺轮式播种器的播种原理,以及播种器行走控制系统的基础上,采用正交试验方法,研究了螺旋勺轮的凹槽深度、螺旋升角、播种器行走速度对播种合格率和空穴率的影响规律,得出杂交稻播种合格率和空穴率影响因素的最佳参数组合:凹槽深度h为3 mm、螺旋升角α为81.73°、播种器行走速度v为0.35 m/s。试验表明,采用闭环控制系统后的播种机播种杂交稻2~6粒/格合格率由87.14%提升到93.21%,常规稻3~8粒/格的播种合格率为92.14%,播种性能满足常规稻和杂交稻精密播种育秧的技术要求。  相似文献   

Alfalfa (Medicago sativa L.) water use efficiency as affected by harvest traffic and soil compaction in a sandy loam soil     

E. A. Rechel  W. R. DeTar  B. D. Meek  L. M. Carter 《Irrigation Science》1991,12(2):61-65

Summary Traffic during alfalfa harvest operations can cause soil compaction and damage to newly growing stems. Root exploration for soil water and nutrients, forage growth dynamics, and final yield can all be affected. The objectives of this study were to determine the long-term effects of harvest traffic and soil compaction on water-use efficiency (WUE) of alfalfa grown in a Wasco sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents). Alfalfa was planted into tilled soil and managed with or without harvest traffic. Plants subjected to traffic during harvest had a significantly lower WUE two out of the three years studied compared to plants that were never subject to traffic. The second experiment examined whether planting alfalfa into compacted soil and managed with or without harvest traffic altered WUE. Soil compaction had no affect on alfalfa WUE. It was significantly lower when grown in compacted soil and subjected to harvest traffic. It is suggested that the decrease in WUE caused by harvest traffic may be explained by plants allocating carbohydrates to damaged shoots and crowns instead of to above ground forage production. The area of the field affected by harvest traffic, which damages newly growing stems, should be minimized to increase crop water use efficiency.  相似文献   

Design and evaluation of an irrigation system for creating water gradients under an automatic rain shelter     

R. L. McCown  B. H. Wall  P. S. Carberry  J. N. G. Hargreaves  K. L. Green  P. L. Poulton 《Irrigation Science》1990,11(3):189-195

Summary This paper reports on the design and performance of an irrigation system associated with a rain shelter. The shelter is used in the closed position as a platform for multiple spray lines. This system automatically supplies, at a specified time, water of specified depth and delivery rate, either uniformly or on a specified gradient across the sheltered area. Variations in crop water deficits and yields have conformed closely to imposed water gradients.  相似文献   

Simulation of the intake and partition of nutrients by the dairy cow: Part I — Management control in the dairy enterprise; philosophy and general model construction     

A. C. Bywater  J. B. Dent 《Agricultural Systems》1976,1(4):245-260

The development of management control techniques for the dairy derd is discussed in this paper in relation to the rationale behind the construction of a detailed model of milk production in the individual cow. The movement towards a more flexible and individualised basis for predicting yield, which does not depend on historical records or standard energy systems, is highlighted.The overall concept and approach of the model are set out and the control aspects and structural framework of the program explained. Subsequent papers in the series will deal in more detail with the major sections of the program in order to illustrate how the mechanisms of the model actually operate and to provide results and an account of the validation procedure.  相似文献   

Measuring yield-reducing plant water potential depressions in wheat by infrared thermometry   总被引：1，自引：0，他引：1  

Idso  S. B.  Reginato  R. J.  Jackson  R. D.  Pinter  P. J. 《Irrigation Science》1981,2(4):205-212

Summary Measurements of foliage and air wet- and dry-bulb temperatures were made over six differentially irrigated plots of Produra wheat grown at Phoenix, Arizona, in the spring of 1976. These data were used to evaluate a newly developed plant water stress index each day from the initiation of heading to the commencement of senescence. Daily measurements on total plant water potential were also obtained over this period; and after demonstrating how the atmospheric-induced component can be removed from these data, the resultant soil-induced component was plotted as a function of the new water stress index. The result was a simple linear relationship, which was found to be identical to one previously derived for alfalfa. Finally, it was shown that grain yield was directly related to the mean plant water stress index over the reproductive growth period from heading to senescence.Contribution from Agricultural Research, Science and Education Administration, US Department of AgricultureResearch physicist, soil scientist, research physicist, and research entomologist, respectively  相似文献   

Control of irrigation amounts using velocity and position of wetting front     

B. Zur  U. Ben-Hanan  A. Rimmer  A. Yardeni 《Irrigation Science》1994,14(4):207-212

A new approach for the estimation and control of the quantity of water applied in an irrigation is presented in which irrigation is stopped when the wetting front reaches a critical depth, Z _L. An expression for calculating the critical depth Z _L was developed. A major parameter in this expression is the velocity of advance of the wetting front, V, which was shown to be directly related to the application rate, IR, and inversely related to the initial soil water content, _i. A depth probe (patent pending) was designed, constructed and tested for the purpose of monitoring the position of the wetting front during infiltration and redistribution and for computing the value of V. Equations developed for relating the velocity of advance of the wetting front to _i as well as for estimating the value of the critical depth Z _L were successfully tested under conditions of uniform distribution of the initial soil water content. An iterative learning process which utilizes the real time output from the depth probe during each irrigation and is therefore capable of handling realistic field conditions where nonuniformity is the rule is presented. The acquired information is used to estimate a critical depth of the wetting front, Z _L, for a planned final wetted depth, Z _F, during each irrigation. This process is incorporated in the depth probe and is used to stop irrigation and thus control the quantity of water applied.  相似文献   

Real-time adaptive irrigation scheduling under a limited water supply   总被引：5，自引：0，他引：5  

N. H. Rao  P. B. S. Sarma  Subhash Chander 《Agricultural Water Management》1992,20(4):267-279

The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study.  相似文献   

Water requirement of Aloe vera in a dry caribbean climate     

Willem B. M. Genet  Cok A. M. van Schooten 《Irrigation Science》1992,13(2):81-85

Summary As hardly any data can be found on the water requirement and yield response to water of Aloe vera, an irrigation experiment on transplanted aloe poles was conducted on the Caribbean island of Aruba. Compared to non-irrigated treatments irrigation shows a positive influence on growth, number of developed leaves, raw gel figure and gel production per plant. The amount of irrigation water to apply can be best calculated based on crop coefficients (K_c) between 0.20 and 0.30. Treatment based on a K_c value higher than 0.30 did not further increase production. A lysimeter study conducted over a relatively short period revealed that the crop coefficient for Aloe vera varied between 0.25 and 0.40 which is characteristic of the so-called agave/pineapple group.  相似文献   

Relations between relative evapotranspiration and predawn leaf water potential in soybean grown in several locations     

B. Itier  D. Flura  K. Belabbes  P. Kosuth  G. Rana  L. Figueiredo 《Irrigation Science》1992,13(3):109-114

Summary The measurement of water consumption in the field is normally restricted to research purposes, although the development of practical field criteria for timing water application is required to improve crop productivity. To develop such criteria irrigation experiments on Soybean were conducted from flowering to grain filling at four locations which differed in their soil properties and the convective contribution of their climates to potential evapotranspiration. The energy balance, predawn leaf water potential (PLWP), soil moisture depletion, and a crop water stress index (CWSI) based on foliage temperature were measured. The range of soil, atmospheric, phenological and irrigation conditions, produced a common, linear relation between relative evapotranspiration (rET) and the logarithm of -PLWP. Correlation with the temperature based CWSI was weak. A similar relation with PLWP for other C₃ plants was also derived from data in the literature. This relation could be helpful for irrigation scheduling once the critical values of rET for crop productivity are known.  相似文献   

Photosynthesis,plant growth and dry matter distribution in kiwifruit as influenced by water deficits   总被引：1，自引：0，他引：1  

K. Chartzoulakis  B. Noitsakis  I. Therios 《Irrigation Science》1993,14(1):1-5

The effects of water deficits on photosynthesis, plant growth and dry matter accumulation and distribution in the kiwifruit, cv Hayward, grown under controlled conditions in the glasshouse were studied. Water stress was imposed by irrigating the plants with 100%, 85%, 65% and 40% of water needed to reach pot capacity in the soil. Water deficits reduced the rate of photosynthesis by up to 53–64% in relation to the control. This decline was attributed to stomatal closure, since stomatal conductance was reduced significantly, or/and to inhibition of photosynthesis at chloroplast level. Severe water stress reduced plant height by 78–84%, total dry weight by 58–66% and total leaf area by 72–77%. The root to shoot ratio was 3.5 times higher in water-stressed plants, showing that water stress in kiwifruit alters the pattern of dry matter distribution favouring the roots. The decrease in growth induced by water deficits was a consequence of a reduction in both photosynthesis and photosynthates partitioning, which adversely affects leaf area development.  相似文献