Soil Water Resources Utilization Limit by Red Plum Apricot Zhongsheng Guo1,2 1,Institute of Soil and Water Conservation, Northwestern A & F University, 2,Institute of Soil and Water Conservation, CAS & MWR, Yangling, China; 26, Xinong Road, Yangling, Shaanxi Province 712100, P. R. China Tel. ++86-29-87012411 Fax. ++86-29-8701-2210 Corresponding Author: zhongshenguo@sohu.com
ABSTRACT:Red plum apricot is a deciduous fruit tree and the best cash forest in semiarid loess hilly regions. Since 1995, the distribution area of red plum apricot spreads in the most of the water-limited regions, China. The yield, benefits and plantation area of red plum apricot increase dramatically. But along with the growth of red plum apricot tree, soil drying appeared and sometime become sever,which influence the yield,quality and benefits of red plum apricot. At this time, the relationship between the soil water and red plum apricot growth must be regulated on Soil Water Resource Use Limitation by Plant and Soil Moisture Carrying Capacity for Vegetation. However, there are few studies on the regulation theory. In this study, daily precipitation, soil water suctions at different soil water content were measured, and the maximal infiltration depth and the soil water resource use limitation by red plum apricot was estimated. The results show that wilting coefficient varies with soil depth from 7.98 in surface soil to 7.1% in 240 cm soil depth, and the maximal infiltration depth is 290 cm, and Soil Water Resources use limit by red plum apricot is 212.7 mm. When the soil water resource in the maximal infiltration depth is lower than the limit, the relationship between the soil water and red plum apricot vegetative growth must be regulated in Red Plum Apricot plantation for high quality production of red plum apricot.
Keywords: Red plum apricot growth; water-limited regions;soil drying; soil degradation; wilting coefficient; maximum infiltration depth; Use Limit of Soil Water Resources by Red plum apricot; high quality production of red plum apricot
INTRODUCTION
Soil water limits the ecological situation where plant roots grow, especially in water-limited regions where climate and soil characteristics set the limits of available water for plant growing. Soil water equilibrium plays a vital role for restoration rehabilitation. Therefore, soil water management is very important in agricultural systems (Asgarzadeh et al. 2014).
In recent years, agricultural production activity has been strenthened to meet the food need of an increasing population worldwide, the intensification of agricultural activity coexisted negative environmental influence (Maharjan et al. 2016). Along with population increase in the water-limited regions, such as in the semiarid loess hilly region of Loess plateau, People need a lot of food, fruit, fiber, etc, and original vegetation has been destroyed and change into farmland. As a result, forest and vegetation is scarcity, and the loss of soil and water in the Loess Plateau had become a serious environmental problem by 1949. Loss of soil and water eroded fertile surface soil and led to soil fertility and crop productivity reduced, which influence quality of human life. In order to conserve soil and water loss, relief of destruction caused by sandstorms and haze weather, increase crop productivity and the improvement of ecological environment, the government has been taking many measures since 1950. In particular, with the implementation of Three-North Shelter Forest Program sponsored in 1978 for 50 years, large-scale afforestation and fruit trees has been carried out on the Loess Plateau. As a result of these efforts, great achievements have been made. The forest coverage fast increased and annual sediment discharge on the Loess plateau has been reduced from 1.6 billion tons in the 1970s to 0.31 billion tons in recent years, and the runoff has been halved.
Because soil in this region is very deep and in the range of 30–80 m from the surface (zhu et al. 1983), and the groundwater table is also deep (Yang and Shao, 2000), and without irrigation, soil water mainly comes from some precipitation penetrating through the canopy. Along with canopy and the roots development, the interception by canopies increase and the roots of these plants grow quickly and thus take up water from considerable soil depths, which reduces the soil water supply and increases soil water consumption. Consequently, the increased water use by plants and interception and low infiltration capacity and soil water recharge rates has led to serious soil drying with times going by (Guo and Li 2009). The dried soil layers(DSL)appeared and then its thickness of DSL increased, and soil drying widespread (Li 1983; Chen et al. 2007). Serious drying of soil eventually and poor self-regulation of plant result in soil degradation, vegetation decline and agriculture failure, which have adverse effects on sustainable use of soil water resources and the stability of forest vegetation ecosystems (Guo and Shao 2013). Thus we should take effective measures to regulate the nonequilibrium relationship between soil water and plant growth (RBSWPG) by reducing the population quantity or density of indicator plants in a plant community on soil water carrying capacity for vegetation (SWCCV) on the Loess Plateau to balance the soil water recharge and soil water consumption in plantation (Guo and Shao 2003; Guo 2014,2021) because soil in this region range from 30 to 80 m from the surface (zhu et al. 1983), and the groundwater table is also deep (Yang and Shao 2000),without irrigation.
The concept of soil water resources come in 1985 (Budagovski 1985; Budagovski and Busarova 1992) after Lvovich proposed the concept of overall soil moistening in 1980. Soil water resources have different meaning in different field, such as Geology, Soil Science, Agriculture, Forestry and Animal Husbandry. In order to meet the need of different specialty, soil water resources can be classified into static soil water resources and dynamic soil water resources. Static soil water resources include generalized and narrow soil water resources. The generalized soil water resources refers the water storage in the soil from surface soil to water table, and narrow soil water resources refers the water storage in the root zone soil, and dynamic soil water resources refers the antecedent soil storage plus the soil water supply from precipitation in the growing season for deciduous plant or a year for evergreen plants. Soil water resources are renewable water resources, a component of water resources (Guo 2014).
The state of vertical distribution of soil water in the root soil zone space influence plant growth. Since drought is a recurring natural phenomenon, and the soil in which plant root distribute resembles a reservoirs and have the storage capacity of water, which have the buffering effect of soil drying on plant growth, the effects of water stress on plant growth vary with the their gravity in these regions. Soil Water Resources Use Limit by Plant is the soil water storage in the maximum infiltration depth(MID) when soil water content in all of the soil layers of the MID equals wilting coefficient (Guo 2010, 2014 ).We do not regulate the relationship as soil drought happens until the soil water resources reduce to a degree (Soil Water Resources Use Limit by Plant ) because when soil water resources in the maximum infiltration depth equal Soil Water Resources Use Limit by Plant, soil water seriously influence plant growth if the duration dry climate continue surpass the key period of regulation of the relationship between soil water and plant growth because plant have some self-regulation power .
Red plum apricot is a deciduous fruit tree and the best cash forest in semiarid loess hilly regions. Since having been selected as good varieties to popularize in 1995, the distribution area of red plum apricot spreads from Guyuan county to the whole Ningxia, and then to Gansu province and so on in the most of the water-limited regions, China,the yield, benefits and planting area of red plum apricot increase doubly. But along with the growth of red plum apricot and precipitation, sometime soil drying become severer. Once serious drying happens, which led to the change of red plum apricot tree leaf colour from green to yellow or croci and drop earlier of the leaf. If serious drying happens in the fruit expansion stage, the size of red plum apricot fruit cannot expand to normal size, which influence the yield, quality and economic benefits of red plum apricot forest. At this time, the relationship between the soil water and red plum apricot growth must be regulated on Soil Water Resources Use Limit by Plant and Soil Water Carrying Capacity for Vegetation to reduce or evade the bad influence of soil drought on the yield and benefits of red plum apricot (Guo 2014,2021). However, there are few studies of Use Limit of Soil Water by red plum apricot.
In the present work, the study aims at achieving these objectives: (1) the changes of cumulative infiltration depths with time and the maximum cumulative infiltration depth in the red plum apricot forest ; (2) Change of wilting coefficient with soil depth up to maximum infiltration depth; and (3) Use Limit of soil Water by red plum apricot.
Methods