FALL SEMESTER - October 21

October 21

Today we talked about N and P in agriculture. 

Fertilizer run-off in agricultural systems can compromise water quality at the regional level. The detrimental effects on the ecosystems are cost effective and difficult to manage. According to a new study in Science, there are now 405 identified dead zones worldwide as the direct result of fertilizer runoff and fossil-fuel use lead to massive areas in the ocean with scant or no oxygen, killing large swaths of sea life and causing hundreds of millions of dollars in damage

This is no small economic matter. As it stands, roughly 83,000 tons (75,000 metric tons) of fish and other ocean life are lost to the Chesapeake Bay dead zone each year

More than 212,000 metric tons [235,000 tons] of food is lost to hypoxia in the Gulf of Mexico

The primary culprit in marine environments is nitrogen and, nowadays, the biggest contributor of nitrogen to marine systems is agriculture.

So much nitrogen is now reaching these coastal waters that much of it ends up buried in sediment, even when new nitrogen sources are removed through sound agricultural practices, those sediments release that nitrogen over time, perpetuating the cycle.

Many studies had looked into integrated management systems to mitigate the effects. 

Effect of Surface Incorporation of Broiler Litter Applied to

No-Till Cotton on Runoff Quality

Adeli et al. 2011

Since surface application of broiler litter to no-till cotton could lead to degradation of water quality…

A 2-yr field study was conducted on a silt loam upland soil to determine the effect of incorporation of broiler litter into the soil surface on nutrient and bacterial transport in runoff.

The experimental design was a randomized complete block with four treatments and three replications: (i) unfertilized control; (ii) surface-applied broiler litter without incorporation; (iii) surface-applied broiler litter with immediate incorporation; and (iv) inorganic fertilizer N and inorganic fertilizer P.

Runoff was collected from small runoff plots (2.4 m by 1.6 m) established at the bottom side of main plots (13.7 m by 6.0 m).

Incorporation of broiler litter reduced total N, NO3-N, water soluble P, and total P concentrations in runoff by 35, 25, 61, and 64%, respectively, and litter-associated bacteria by two to three orders of magnitude compared with unincorporated treatment.