Large diversity of micro flora and fauna are found in soil horizons. Microbial population in soil are determined by various factor such as soil depth, organic matter, porosity, oxygen and carbon dioxide concentration, soil PH, etc. Factors that influence microorganism role in nutrient building and cycling in soil and organic matter decomposition are of unique interest. Microorganisms decompose organic matter, detoxifying the toxic substance, fixing the nitrogen, transformation of nitrogen, phosphorous, potassium and other secondary & micro nutrients are the major biochemical activities performed by microbes in soil. Low population of microorganism is found in the compact soil, soil with low organic matter percentage and on deeper strata of soil. So, this paper was reviewed to explore major factors that influence soil microbial population and its role in soil productivity. This was already established fact but main aim of this paper is to collect related information and conclude the future research prospects to strengthen the microorganism role in soil productivity and factor that influence growth of microorganism.

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The declining Ogallala aquifer in the Texas High Plains may no longer meet the irrigation requirement to produce high water‐demanding forage crops like silage corn (Zea mays L.) to support a large number of beef and dairy enterprises. Forage sorghum (Sorghum bicolor L.) and pearl millet (Pennisetum glaucum L.) can be viable alternatives to silage corn due to their relative drought tolerance than silage corn. A field experiment was conducted at New Deal, TX to assess and compare the physiology, forage yield, and nutrient composition of the brown midrib (BMR) forage sorghum, BMR pearl millet, and corn under deficit irrigation in 2018 and 2019. The experiment was conducted in a split‐plot design with three irrigation levels (I0 [50 mm], I1 [200 mm], and I2 [350 mm]) as main‐plot and five cultivars (P1498AM [corn], AF7401 and Silo700D [BMR sorghum], and Epic and Exceed [BMR pearl millet]) as sub‐plot with four replications. The higher leaf water potential (LWP), stomatal conductance, and leaf area index resulted in greater biomass assimilation in I2 compared to I1 and I0 irrigation treatments in both years. Sorghum and pearl millet cultivars showed lower water status through lower LWP and canopy‐air temperature difference compared to corn cultivar. However, sorghum cultivars yielded greater fresh biomass than pearl millet and corn in both years. Lower lignin concentration and higher digestible energy were observed in corn, followed by pearl millet and sorghum. These results suggest that under water‐stress conditions BMR sorghum can produce higher forage yield with acceptable nutritive value.

Core Ideas• Declining groundwater supplies, the increasing cost of irrigation, and excessive summer dryness threaten the sustainability of corn production in the Texas High Plains (THP).• Forage sorghum and pearl millet are potential alternatives to corn silage.• Sorghum and pearl millet are likely to replace much of the corn silage crop in the THP. AbstractDiminishing irrigation water from the Ogallala aquifer to produce forage crops is jeopardizing the beef and dairy industries in the Texas High Plains (THP). The principal feed ingredient of the beef and dairy sectors is corn (Zea mays L.) silage, which is produced near the feeding operations to minimize transport costs, unlike concentrated feed, which can be transported long distances. The declining pumping capacity of irrigation wells hinders the ability to sustain a supply of water for profitable corn production in the THP. Forage sorghum [Sorghum bicolor (L.) Moench] and pearl millet [Pennisetum glaucum (L.) R. Br.] are known for their ability to tolerate drought and heat, which enables them to produce high forage yields with less water than corn. Pearl millet and sorghum can also be harvested as hay, greenchop, or silage like corn. Introduction of the brown midrib (BMR) trait into pearl millet and sorghum has enhanced their nutrient composition. Brown midrib is a genetic trait associated with reduced lignin synthesis, resulting in enhanced digestion of forage fiber in the bovine (Bos taurus) rumen, thereby increasing weight gain and milk production per ton of forage fed over non-BMR types. Therefore, BMR forage sorghum and BMR pearl millet could be potential alternative forage crops where water is insufficient to grow corn silage in the THP. Hence, the objective of this review paper is to compare the water use efficiency, nutritional composition, associated antinutritional compounds, animal performance, and potential yields of BMR forage sorghum and BMR pearl millet with corn.

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