Comparative effectiveness of animal manures on soil chemical properties, yield and root growth of amaranthus (Amaranthus cruentus L.)

Abstract

Pot and field experiments were conducted to compare the effects of dairy cow, goat and poultry manures on soil available levels of N and P and amaranths yield and root growth. The three amendments were applied on Oxisols at 100, 150 and 170 kg N/ha in a split plot design and replicated three times. Pot experiment lasted for one month whereas field experiment was conducted over three monthly crop cycles. Results of both experiments indicated that applications of the three manures significantly (P < 0.01) increased soil available levels of N and P shoot dry matter yield, taproot length and root dry weight. Comparison of the responses from the three manures revealed that for all the parameters evaluated the trend was; Poultry manure > goat manure > dairy cow manure. This was largely attributed to differences in total N, total P, C/N and C/P ratios of the amendments. Field experiment results revealed that responses were highest after the third crop harvest suggesting that mineralization of organic N and P increased with time. Based on fertilizer recommendations of N and P for Southern highlands of Tanzania and the highest rate used in this study (170 kg N/ha), applications of 5.8 tons/ha, 9.8 tons/ha and 13.4 tons/ha of poultry, goat and dairy cow manure will suffice the requirement of 40 kg N/ha and 20 kg P/ha recommended for most field crops.