Impact of Forage Fertilization with Urea and Composted Cattle Manure on Soil Fertility in Sandy Soils of South-Central Vietnam

Table 7

Dry matter yield, partial N, P, and K balances, and nitrogen recovery, by composted manure and urea treatment combinations.

Compost rate	Urea rate	Yield	N balance	P balance	K balance	Nitrogen recovery
						Sept 2011	Dec 2012
(Mg DM/ha per yr)	(kg N/ha per yr)	(Mg DM/ha per yr)	(kg N/ha per yr)	(kg P/ha per yr)	(kg K/ha per yr)	(%)	(%)
24	120	18.3	−67 bc	−5 b	−241 bc	34.0 ab	42.2 ab
24	60	12.5	32 a	17 a	−123 a	3.0 b	−7.8 b
24	0	11.7	−8 ab	20 a	−104 a	−8.5 b	−12.4 b
12	120	15.4	−113 cd	−25 d	−258 cd	22.4 ab	23.0 b
12	60	15.7	−168 def	−25 d	−247 bc	21.4 ab	32.7 ab
12	0	12.2	−153 de	−13 c	−192 b	−10.7 b	−20.4
8	120	15.3	−155 de	−36 e	−263 cd	21.0 ab	30.3 ab
8	60	13.3	−160 de	−28 d	−230 bc	0.5 b	−0.6 b
8	0	12.8	−208 efg	−26 d	−216 bc	−13.1 b	−13.0 b
4	120	14.1	−181 def	−42 fg	−248 bc	23.4 ab	17.9 b
4	60	16.7	−307 hi	−52 h	−316 d	78.5 a	112.2 a
4	0	12.8	−264 ghi	−38 ef	−240 bc	1.1 b	−10.8 b
0	120	13.6	−202 efg	−49 h	−280 cd	10.6 ab	5.0 b
0	60	12.5	−236 fgh	−47 gh	−276 cd	−13.5 b	−42.2 b
0	0	12.6	−312 i	−47 gh	−240 bc	—	—

Balances were calculated using overall dry matter yield treatment means and plot treatment nutrient concentrations from September 2011 and December 2012 samples.
Means not connected by the same letter in each column are significantly different ().
Nitrogen recovery was calculated according to Jokela and Randall [20] as  % N recovery = [(N uptake in treatment − N uptake in zero N control)/total N applied in treatment] × 100. Nitrogen recovery was based on overall dry matter yield treatment means and application rates in September 2011 and December 2012.