Effects of Composition and Rainfall on the Quality of Manure from Small-Scale Manure Storage Systems in Kenya.

Because manure is the most commonly used soil amendment in much of sub-Saharan Africa, knowledge of its nutrient contributions is important to maintaining soil fertility.  This study was designed to determine: 1)  when N losses occur during manure storage, 2) how urine affects manure mineral-N and neutral detergent fiber-bound N (NDIN), 3) leaching losses from storage, and 4) how rainfall affects manure composition.  In a spatially-balanced complete block experiment, cattle manure from two Kenyan farms was stored with and without urine during dry and rainy seasons. Farm 2 manure quality was superior to Farm 1.  Manure was sampled destructively 10 times over a 120-d storage period and leachates were collected throughout.  Preliminary data: 

Farm	Season		Treatment			Storage days	Treatment
			No urine	Urine			No urine	Urine
1	Dry	Initial NDIN	32.4	32.4	%NDIN lostsd	30	24.72.1	34.35.3
2	Dry	g/kg	41.3	41.3		30	30.67.4	56.58.3
1	Dry		---	---		120	37.11.8	60.31.8
2	Dry		---	---		120	55.47.3	79.41.1
1	Rainy		38.0	38.0		30	38.417.3	10.43.1
2	Rainy		36.3	36.3		30	30.66.4	15.58.2

Mineral-N concentrations tripled after 30 d and were twice the initial concentrations after 120 d in manure with urine.  Without urine, the initial and final mineral-N concentrations were the same while the 30 d mineral-N concentration was 1.5 the initial.  Urine did not affect the leachate NH₄-N content (P>0.01).  Addition of urine to the dry season manure resulted in lower NDIN levels (P<0.01) and higher mineral-N levels (P<0.05).  This was not observed during the rainy season.  Cattle waste may be stored in an uncovered system during dry seasons.  During rains, covering the storage system prevents leaching due to rainfall so that the advantages of urine inclusion are realized. To exploit the mineral-N before it is leached, manure should not be stored more than 30 d before soil application.